diff --git a/CHANGES b/CHANGES
index f3b20a9242..209f724d3b 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,4 +1,10 @@
 
+3.2.0-dev.378 | 2020-04-09 08:47:44 -0700
+
+  * Replace most of the uses of 0 or NULL to indicate null pointers with nullptr.
+    This change does not change any calls to syscalls, in the interest of passing
+    what the API for those calls says to pass. (Tim Wojtulewicz, Corelight)
+
 3.2.0-dev.372 | 2020-04-08 14:00:28 -0700
 
   * Lazy-initalize some of the fields in Frame to reduce size (Tim Wojtulewicz, Corelight)
diff --git a/VERSION b/VERSION
index 73ecc2b0ae..4ea7de2eb6 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-3.2.0-dev.372
+3.2.0-dev.378
diff --git a/src/Anon.cc b/src/Anon.cc
index 4c54510217..41544ab8c8 100644
--- a/src/Anon.cc
+++ b/src/Anon.cc
@@ -12,7 +12,7 @@
 #include "Reporter.h"
 
 
-AnonymizeIPAddr* ip_anonymizer[NUM_ADDR_ANONYMIZATION_METHODS] = {0};
+AnonymizeIPAddr* ip_anonymizer[NUM_ADDR_ANONYMIZATION_METHODS] = {nullptr};
 
 static uint32_t rand32()
 	{
@@ -148,7 +148,7 @@ AnonymizeIPAddr_A50::~AnonymizeIPAddr_A50()
 
 void AnonymizeIPAddr_A50::init()
 	{
-	root = next_free_node = 0;
+	root = next_free_node = nullptr;
 
 	// Prepare special nodes for 0.0.0.0 and 255.255.255.255.
 	memset(&special_nodes[0], 0, sizeof(special_nodes));
@@ -222,7 +222,7 @@ AnonymizeIPAddr_A50::Node* AnonymizeIPAddr_A50::new_node_block()
 	for ( int i = 1; i < block_size - 1; ++i )
 		block[i].child[0] = &block[i+1];
 
-	block[block_size - 1].child[0] = 0;
+	block[block_size - 1].child[0] = nullptr;
 	next_free_node = &block[1];
 
 	return &block[0];
@@ -276,12 +276,12 @@ AnonymizeIPAddr_A50::Node* AnonymizeIPAddr_A50::make_peer(ipaddr32_t a, Node* n)
 	Node* down[2];
 
 	if ( ! (down[0] = new_node()) )
-		return 0;
+		return nullptr;
 
 	if ( ! (down[1] = new_node()) )
 		{
 		free_node(down[0]);
-		return 0;
+		return nullptr;
 		}
 
 	// swivel is first bit 'a' and 'old->input' differ.
@@ -292,7 +292,7 @@ AnonymizeIPAddr_A50::Node* AnonymizeIPAddr_A50::make_peer(ipaddr32_t a, Node* n)
 
 	down[bitvalue]->input = a;
 	down[bitvalue]->output = make_output(n->output, swivel);
-	down[bitvalue]->child[0] = down[bitvalue]->child[1] = 0;
+	down[bitvalue]->child[0] = down[bitvalue]->child[1] = nullptr;
 
 	*down[1 - bitvalue] = *n;	// copy orig node down one level
 
@@ -316,7 +316,7 @@ AnonymizeIPAddr_A50::Node* AnonymizeIPAddr_A50::find_node(ipaddr32_t a)
 		root = new_node();
 		root->input = a;
 		root->output = rand32();
-		root->child[0] = root->child[1] = 0;
+		root->child[0] = root->child[1] = nullptr;
 
 		return root;
 		}
@@ -351,12 +351,12 @@ AnonymizeIPAddr_A50::Node* AnonymizeIPAddr_A50::find_node(ipaddr32_t a)
 		}
 
 	reporter->InternalError("out of memory!");
-	return 0;
+	return nullptr;
 	}
 
 void init_ip_addr_anonymizers()
 	{
-	ip_anonymizer[KEEP_ORIG_ADDR] = 0;
+	ip_anonymizer[KEEP_ORIG_ADDR] = nullptr;
 	ip_anonymizer[SEQUENTIALLY_NUMBERED] = new AnonymizeIPAddr_Seq();
 	ip_anonymizer[RANDOM_MD5] = new AnonymizeIPAddr_RandomMD5();
 	ip_anonymizer[PREFIX_PRESERVING_A50] = new AnonymizeIPAddr_A50();
@@ -365,7 +365,7 @@ void init_ip_addr_anonymizers()
 
 ipaddr32_t anonymize_ip(ipaddr32_t ip, enum ip_addr_anonymization_class_t cl)
 	{
-	TableVal* preserve_addr = 0;
+	TableVal* preserve_addr = nullptr;
 	AddrVal addr(ip);
 
 	int method = -1;
diff --git a/src/Attr.cc b/src/Attr.cc
index ea735b67f0..bf39c7f9c9 100644
--- a/src/Attr.cc
+++ b/src/Attr.cc
@@ -197,7 +197,7 @@ void Attributes::AddAttrs(Attributes* a)
 Attr* Attributes::FindAttr(attr_tag t) const
 	{
 	if ( ! attrs )
-		return 0;
+		return nullptr;
 
 	for ( const auto& a : *attrs )
 		{
@@ -205,7 +205,7 @@ Attr* Attributes::FindAttr(attr_tag t) const
 			return a;
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 void Attributes::RemoveAttr(attr_tag t)
diff --git a/src/Base64.cc b/src/Base64.cc
index 51d2b707ad..16e43d296c 100644
--- a/src/Base64.cc
+++ b/src/Base64.cc
@@ -55,7 +55,7 @@ int* Base64Converter::InitBase64Table(const string& alphabet)
 	if ( alphabet == default_alphabet && default_table_initialized )
 		return default_base64_table;
 
-	int* base64_table = 0;
+	int* base64_table = nullptr;
 
 	if ( alphabet == default_alphabet )
 		{
@@ -98,7 +98,7 @@ Base64Converter::Base64Converter(Connection* arg_conn, const string& arg_alphabe
 		alphabet = default_alphabet;
 		}
 
-	base64_table = 0;
+	base64_table = nullptr;
 	base64_group_next = 0;
 	base64_padding = base64_after_padding = 0;
 	errored = 0;
@@ -234,7 +234,7 @@ BroString* decode_base64(const BroString* s, const BroString* a, Connection* con
 		{
 		reporter->Error("base64 decoding alphabet is not 64 characters: %s",
 		                a->CheckString());
-		return 0;
+		return nullptr;
 		}
 
 	int buf_len = int((s->Len() + 3) / 4) * 3 + 1;
@@ -259,7 +259,7 @@ BroString* decode_base64(const BroString* s, const BroString* a, Connection* con
 
 err:
 	delete [] rbuf;
-	return 0;
+	return nullptr;
 	}
 
 BroString* encode_base64(const BroString* s, const BroString* a, Connection* conn)
@@ -268,10 +268,10 @@ BroString* encode_base64(const BroString* s, const BroString* a, Connection* con
 		{
 		reporter->Error("base64 alphabet is not 64 characters: %s",
 		                a->CheckString());
-		return 0;
+		return nullptr;
 		}
 
-	char* outbuf = 0;
+	char* outbuf = nullptr;
 	int outlen = 0;
 	Base64Converter enc(conn, a ? a->CheckString() : "");
 	enc.Encode(s->Len(), (const unsigned char*) s->Bytes(), &outlen, &outbuf);
diff --git a/src/Base64.h b/src/Base64.h
index cdebc93017..2348eccc11 100644
--- a/src/Base64.h
+++ b/src/Base64.h
@@ -59,5 +59,5 @@ protected:
 
 };
 
-BroString* decode_base64(const BroString* s, const BroString* a = 0, Connection* conn = 0);
-BroString* encode_base64(const BroString* s, const BroString* a = 0, Connection* conn = 0);
+BroString* decode_base64(const BroString* s, const BroString* a = nullptr, Connection* conn = nullptr);
+BroString* encode_base64(const BroString* s, const BroString* a = nullptr, Connection* conn = nullptr);
diff --git a/src/BroString.cc b/src/BroString.cc
index 33a14a315b..cfd7e92c15 100644
--- a/src/BroString.cc
+++ b/src/BroString.cc
@@ -284,7 +284,7 @@ BroString* BroString::GetSubstring(int start, int len) const
 	{
 	// This code used to live in zeek.bif's sub_bytes() routine.
 	if ( start < 0 || start > n )
-		return 0;
+		return nullptr;
 
 	if ( len < 0 || len > n - start )
 		len = n - start;
@@ -302,7 +302,7 @@ BroString::Vec* BroString::Split(const BroString::IdxVec& indices) const
 	unsigned int i;
 
 	if ( indices.empty() )
-		return 0;
+		return nullptr;
 
 	// Copy input, ensuring space for "0":
 	IdxVec idx(1 + indices.size());
@@ -343,7 +343,7 @@ VectorVal* BroString:: VecToPolicy(Vec* vec)
 	VectorVal* result =
 		new VectorVal(internal_type("string_vec")->AsVectorType());
 	if ( ! result )
-		return 0;
+		return nullptr;
 
 	for ( unsigned int i = 0; i < vec->size(); ++i )
 		{
diff --git a/src/BroString.h b/src/BroString.h
index 40a1029291..66c3bce4b7 100644
--- a/src/BroString.h
+++ b/src/BroString.h
@@ -94,7 +94,7 @@ public:
 	//
 	// Note that you need to delete[] the resulting string.
 	//
-	char* Render(int format = EXPANDED_STRING, int* len = 0) const;
+	char* Render(int format = EXPANDED_STRING, int* len = nullptr) const;
 
 	// Similar to the above, but useful for output streams.
 	// Also more useful for debugging purposes since no deallocation
diff --git a/src/Brofiler.cc b/src/Brofiler.cc
index c406182747..a2391145cd 100644
--- a/src/Brofiler.cc
+++ b/src/Brofiler.cc
@@ -76,7 +76,7 @@ bool Brofiler::ReadStats()
 
 		pair<string, string> location_desc(std::move(location), std::move(desc));
 		uint64_t count;
-		atoi_n(cnt.size(), cnt.c_str(), 0, 10, count);
+		atoi_n(cnt.size(), cnt.c_str(), nullptr, 10, count);
 		usage_map.emplace(std::move(location_desc), count);
 		}
 
diff --git a/src/CompHash.cc b/src/CompHash.cc
index b28c9e307b..7d9a29da62 100644
--- a/src/CompHash.cc
+++ b/src/CompHash.cc
@@ -47,19 +47,19 @@ CompositeHash::CompositeHash(IntrusivePtr<TypeList> composite_type)
 		// via the singleton later.
 		singleton_tag = (*type->Types())[0]->InternalType();
 		size = 0;
-		key = 0;
+		key = nullptr;
 		}
 
 	else
 		{
-		size = ComputeKeySize(0, true, true);
+		size = ComputeKeySize(nullptr, true, true);
 
 		if ( size > 0 )
 			// Fixed size.  Make sure what we get is fully aligned.
 			key = reinterpret_cast<char*>
 				(new double[size/sizeof(double) + 1]);
 		else
-			key = 0;
+			key = nullptr;
 		}
 	}
 
@@ -72,7 +72,7 @@ CompositeHash::~CompositeHash()
 char* CompositeHash::SingleValHash(bool type_check, char* kp0,
 				   BroType* bt, Val* v, bool optional) const
 	{
-	char* kp1 = 0;
+	char* kp1 = nullptr;
 	InternalTypeTag t = bt->InternalType();
 
 	if ( optional )
@@ -90,7 +90,7 @@ char* CompositeHash::SingleValHash(bool type_check, char* kp0,
 		{
 		InternalTypeTag vt = v->Type()->InternalType();
 		if ( vt != t )
-			return 0;
+			return nullptr;
 		}
 
 	switch ( t ) {
@@ -186,12 +186,12 @@ char* CompositeHash::SingleValHash(bool type_check, char* kp0,
 				bool optional = (a && a->FindAttr(ATTR_OPTIONAL));
 
 				if ( ! (rv_i || optional) )
-					return 0;
+					return nullptr;
 
 				if ( ! (kp = SingleValHash(type_check, kp,
 							   rt->FieldType(i),
 							   rv_i, optional)) )
-					return 0;
+					return nullptr;
 				}
 
 			kp1 = kp;
@@ -242,7 +242,7 @@ char* CompositeHash::SingleValHash(bool type_check, char* kp0,
 
 				if ( ! (kp1 = SingleValHash(type_check, kp1, key->Type(), key,
 				                            false)) )
-					return 0;
+					return nullptr;
 
 				if ( ! v->Type()->IsSet() )
 					{
@@ -250,7 +250,7 @@ char* CompositeHash::SingleValHash(bool type_check, char* kp0,
 
 					if ( ! (kp1 = SingleValHash(type_check, kp1, val->Type(),
 								    val.get(), false)) )
-						return 0;
+						return nullptr;
 					}
 				}
 
@@ -278,7 +278,7 @@ char* CompositeHash::SingleValHash(bool type_check, char* kp0,
 					{
 					if ( ! (kp1 = SingleValHash(type_check, kp1,
 					                            vt->YieldType(), val, false)) )
-						return 0;
+						return nullptr;
 					}
 				}
 			}
@@ -295,7 +295,7 @@ char* CompositeHash::SingleValHash(bool type_check, char* kp0,
 				Val* v = lv->Index(i);
 				if ( ! (kp1 = SingleValHash(type_check, kp1, v->Type(), v,
 				                            false)) )
-					return 0;
+					return nullptr;
 				}
 			}
 			break;
@@ -303,7 +303,7 @@ char* CompositeHash::SingleValHash(bool type_check, char* kp0,
 		default:
 			{
 			reporter->InternalError("bad index type in CompositeHash::SingleValHash");
-			return 0;
+			return nullptr;
 			}
 		}
 
@@ -326,7 +326,7 @@ char* CompositeHash::SingleValHash(bool type_check, char* kp0,
 		break;
 
 	case TYPE_INTERNAL_ERROR:
-		return 0;
+		return nullptr;
 	}
 
 	return kp1;
@@ -361,7 +361,7 @@ HashKey* CompositeHash::ComputeHash(const Val* v, bool type_check) const
 		{
 		int sz = ComputeKeySize(v, type_check, false);
 		if ( sz == 0 )
-			return 0;
+			return nullptr;
 
 		k = reinterpret_cast<char*>(new double[sz/sizeof(double) + 1]);
 		type_check = false;	// no need to type-check again.
@@ -370,18 +370,18 @@ HashKey* CompositeHash::ComputeHash(const Val* v, bool type_check) const
 	const type_list* tl = type->Types();
 
 	if ( type_check && v->Type()->Tag() != TYPE_LIST )
-		return 0;
+		return nullptr;
 
 	const val_list* vl = v->AsListVal()->Vals();
 	if ( type_check && vl->length() != tl->length() )
-		return 0;
+		return nullptr;
 
 	char* kp = k;
 	loop_over_list(*tl, i)
 		{
 		kp = SingleValHash(type_check, kp, (*tl)[i], (*vl)[i], false);
 		if ( ! kp )
-			return 0;
+			return nullptr;
 		}
 
 	return new HashKey((k == key), (void*) k, kp - k);
@@ -393,13 +393,13 @@ HashKey* CompositeHash::ComputeSingletonHash(const Val* v, bool type_check) cons
 		{
 		const val_list* vl = v->AsListVal()->Vals();
 		if ( type_check && vl->length() != 1 )
-			return 0;
+			return nullptr;
 
 		v = (*vl)[0];
 		}
 
 	if ( type_check && v->Type()->InternalType() != singleton_tag )
-		return 0;
+		return nullptr;
 
 	switch ( singleton_tag ) {
 	case TYPE_INTERNAL_INT:
@@ -434,17 +434,17 @@ HashKey* CompositeHash::ComputeSingletonHash(const Val* v, bool type_check) cons
 			}
 
 		reporter->InternalError("bad index type in CompositeHash::ComputeSingletonHash");
-		return 0;
+		return nullptr;
 
 	case TYPE_INTERNAL_STRING:
 		return new HashKey(v->AsString());
 
 	case TYPE_INTERNAL_ERROR:
-		return 0;
+		return nullptr;
 
 	default:
 		reporter->InternalError("bad internal type in CompositeHash::ComputeSingletonHash");
-		return 0;
+		return nullptr;
 	}
 	}
 
@@ -507,7 +507,7 @@ int CompositeHash::SingleTypeKeySize(BroType* bt, const Val* v,
 
 		case TYPE_RECORD:
 			{
-			const RecordVal* rv = v ? v->AsRecordVal() : 0;
+			const RecordVal* rv = v ? v->AsRecordVal() : nullptr;
 			RecordType* rt = bt->AsRecordType();
 			int num_fields = rt->NumFields();
 
@@ -517,7 +517,7 @@ int CompositeHash::SingleTypeKeySize(BroType* bt, const Val* v,
 				bool optional = (a && a->FindAttr(ATTR_OPTIONAL));
 
 				sz = SingleTypeKeySize(rt->FieldType(i),
-						       rv ? rv->Lookup(i) : 0,
+						       rv ? rv->Lookup(i) : nullptr,
 						       type_check, sz, optional,
 						       calc_static_size);
 				if ( ! sz )
@@ -632,7 +632,7 @@ int CompositeHash::SingleTypeKeySize(BroType* bt, const Val* v,
 int CompositeHash::ComputeKeySize(const Val* v, bool type_check, bool calc_static_size) const
 	{
 	const type_list* tl = type->Types();
-	const val_list* vl = 0;
+	const val_list* vl = nullptr;
 	if ( v )
 		{
 		if ( type_check && v->Type()->Tag() != TYPE_LIST )
@@ -646,7 +646,7 @@ int CompositeHash::ComputeKeySize(const Val* v, bool type_check, bool calc_stati
 	int sz = 0;
 	loop_over_list(*tl, i)
 		{
-		sz = SingleTypeKeySize((*tl)[i], v ? v->AsListVal()->Index(i) : 0,
+		sz = SingleTypeKeySize((*tl)[i], v ? v->AsListVal()->Index(i) : nullptr,
 				       type_check, sz, false, calc_static_size);
 		if ( ! sz )
 			return 0;
@@ -745,7 +745,7 @@ const char* CompositeHash::RecoverOneVal(const HashKey* k, const char* kp0,
 
 	TypeTag tag = t->Tag();
 	InternalTypeTag it = t->InternalType();
-	const char* kp1 = 0;
+	const char* kp1 = nullptr;
 
 	if ( optional )
 		{
diff --git a/src/Conn.cc b/src/Conn.cc
index bc37dea87a..95ee5af8f2 100644
--- a/src/Conn.cc
+++ b/src/Conn.cc
@@ -120,7 +120,7 @@ Connection::Connection(NetSessions* s, const ConnIDKey& k, double t, const ConnI
 	if ( arg_encap )
 		encapsulation = new EncapsulationStack(*arg_encap);
 	else
-		encapsulation = 0;
+		encapsulation = nullptr;
 	}
 
 Connection::~Connection()
@@ -132,7 +132,7 @@ Connection::~Connection()
 
 	if ( conn_val )
 		{
-		conn_val->SetOrigin(0);
+		conn_val->SetOrigin(nullptr);
 		Unref(conn_val);
 		}
 
@@ -148,7 +148,7 @@ void Connection::CheckEncapsulation(const EncapsulationStack* arg_encap)
 		{
 		if ( *encapsulation != *arg_encap )
 			{
-			Event(tunnel_changed, 0, arg_encap->GetVectorVal());
+			Event(tunnel_changed, nullptr, arg_encap->GetVectorVal());
 			delete encapsulation;
 			encapsulation = new EncapsulationStack(*arg_encap);
 			}
@@ -157,14 +157,14 @@ void Connection::CheckEncapsulation(const EncapsulationStack* arg_encap)
 	else if ( encapsulation )
 		{
 		EncapsulationStack empty;
-		Event(tunnel_changed, 0, empty.GetVectorVal());
+		Event(tunnel_changed, nullptr, empty.GetVectorVal());
 		delete encapsulation;
 		encapsulation = nullptr;
 		}
 
 	else if ( arg_encap )
 		{
-		Event(tunnel_changed, 0, arg_encap->GetVectorVal());
+		Event(tunnel_changed, nullptr, arg_encap->GetVectorVal());
 		encapsulation = new EncapsulationStack(*arg_encap);
 		}
 	}
@@ -269,7 +269,7 @@ void Connection::HistoryThresholdEvent(EventHandlerPtr e, bool is_orig,
 void Connection::DeleteTimer(double /* t */)
 	{
 	if ( is_active )
-		Event(connection_timeout, 0);
+		Event(connection_timeout, nullptr);
 
 	sessions->Remove(this);
 	}
@@ -282,7 +282,7 @@ void Connection::InactivityTimer(double t)
 		{
 		if ( last_time + inactivity_timeout <= t )
 			{
-			Event(connection_timeout, 0);
+			Event(connection_timeout, nullptr);
 			sessions->Remove(this);
 			++killed_by_inactivity;
 			}
@@ -402,12 +402,12 @@ RecordVal* Connection::BuildConnVal()
 
 analyzer::Analyzer* Connection::FindAnalyzer(analyzer::ID id)
 	{
-	return root_analyzer ? root_analyzer->FindChild(id) : 0;
+	return root_analyzer ? root_analyzer->FindChild(id) : nullptr;
 	}
 
 analyzer::Analyzer* Connection::FindAnalyzer(const analyzer::Tag& tag)
 	{
-	return root_analyzer ? root_analyzer->FindChild(tag) : 0;
+	return root_analyzer ? root_analyzer->FindChild(tag) : nullptr;
 	}
 
 analyzer::Analyzer* Connection::FindAnalyzer(const char* name)
@@ -696,7 +696,7 @@ void Connection::CheckFlowLabel(bool is_orig, uint32_t flow_label)
 		if ( connection_flow_label_changed &&
 		     (is_orig ? saw_first_orig_packet : saw_first_resp_packet) )
 			{
-			EnqueueEvent(connection_flow_label_changed, 0,
+			EnqueueEvent(connection_flow_label_changed, nullptr,
 				IntrusivePtr{AdoptRef{}, BuildConnVal()},
 				IntrusivePtr{AdoptRef{}, val_mgr->GetBool(is_orig)},
 				IntrusivePtr{AdoptRef{}, val_mgr->GetCount(my_flow_label)},
diff --git a/src/Conn.h b/src/Conn.h
index 53ece49bef..bc33effd57 100644
--- a/src/Conn.h
+++ b/src/Conn.h
@@ -180,13 +180,13 @@ public:
 	// given that event's first argument will be it, and it's second will be
 	// the connection value.  If 'name' is null, then the event's first
 	// argument is the connection value.
-	void Event(EventHandlerPtr f, analyzer::Analyzer* analyzer, const char* name = 0);
+	void Event(EventHandlerPtr f, analyzer::Analyzer* analyzer, const char* name = nullptr);
 
 	// If a handler exists for 'f', an event will be generated.  In any case,
 	// 'v1' and 'v2' reference counts get decremented.  The event's first
 	// argument is the connection value, second argument is 'v1', and if 'v2'
 	// is given that will be it's third argument.
-	void Event(EventHandlerPtr f, analyzer::Analyzer* analyzer, Val* v1, Val* v2 = 0);
+	void Event(EventHandlerPtr f, analyzer::Analyzer* analyzer, Val* v1, Val* v2 = nullptr);
 
 	// If a handler exists for 'f', an event will be generated.  In any case,
 	// reference count for each element in the 'vl' list are decremented.  The
diff --git a/src/DFA.cc b/src/DFA.cc
index e99e772fcc..071a8f9570 100644
--- a/src/DFA.cc
+++ b/src/DFA.cc
@@ -17,7 +17,7 @@ DFA_State::DFA_State(int arg_state_num, const EquivClass* ec,
 	num_sym = ec->NumClasses();
 	nfa_states = arg_nfa_states;
 	accept = arg_accept;
-	mark = 0;
+	mark = nullptr;
 
 	SymPartition(ec);
 
@@ -96,7 +96,7 @@ DFA_State* DFA_State::ComputeXtion(int sym, DFA_Machine* machine)
 	else
 		{
 		delete ns;
-		next_d = 0;	// Jam
+		next_d = nullptr;	// Jam
 		}
 
 	AddXtion(equiv_sym, next_d);
@@ -182,7 +182,7 @@ void DFA_State::ClearMarks()
 	{
 	if ( mark )
 		{
-		SetMark(0);
+		SetMark(nullptr);
 
 		for ( int i = 0; i < num_sym; ++i )
 			{
@@ -395,7 +395,7 @@ DFA_Machine::DFA_Machine(NFA_Machine* n, EquivClass* arg_ec)
 		}
 	else
 		{
-		start_state = 0; // Jam
+		start_state = nullptr; // Jam
 		delete ns;
 		}
 	}
@@ -451,7 +451,7 @@ bool DFA_Machine::StateSetToDFA_State(NFA_state_list* state_set,
 	if ( accept->empty() )
 		{
 		delete accept;
-		accept = 0;
+		accept = nullptr;
 		}
 
 	DFA_State* ds = new DFA_State(state_count++, ec, state_set, accept);
diff --git a/src/DNS_Mgr.cc b/src/DNS_Mgr.cc
index e0bc8ffe90..b39ba83aab 100644
--- a/src/DNS_Mgr.cc
+++ b/src/DNS_Mgr.cc
@@ -194,7 +194,7 @@ DNS_Mapping::DNS_Mapping(const IPAddr& addr, struct hostent* h, uint32_t ttl)
 	{
 	Init(h);
 	req_addr = addr;
-	req_host = 0;
+	req_host = nullptr;
 	req_ttl = ttl;
 	}
 
@@ -203,7 +203,7 @@ DNS_Mapping::DNS_Mapping(FILE* f)
 	Clear();
 	init_failed = true;
 
-	req_host = 0;
+	req_host = nullptr;
 	req_ttl = 0;
 	creation_time = 0;
 
@@ -255,7 +255,7 @@ DNS_Mapping::DNS_Mapping(FILE* f)
 			}
 		}
 	else
-		addrs = 0;
+		addrs = nullptr;
 
 	init_failed = false;
 	}
@@ -302,7 +302,7 @@ IntrusivePtr<TableVal> DNS_Mapping::AddrsSet() {
 IntrusivePtr<StringVal> DNS_Mapping::Host()
 	{
 	if ( failed || num_names == 0 || ! names[0] )
-		return 0;
+		return nullptr;
 
 	if ( ! host_val )
 		host_val = make_intrusive<StringVal>(names[0]);
@@ -315,8 +315,8 @@ void DNS_Mapping::Init(struct hostent* h)
 	no_mapping = false;
 	init_failed = false;
 	creation_time = current_time();
-	host_val = 0;
-	addrs_val = 0;
+	host_val = nullptr;
+	addrs_val = nullptr;
 
 	if ( ! h )
 		{
@@ -327,7 +327,7 @@ void DNS_Mapping::Init(struct hostent* h)
 	map_type = h->h_addrtype;
 	num_names = 1;	// for now, just use official name
 	names = new char*[num_names];
-	names[0] = h->h_name ? copy_string(h->h_name) : 0;
+	names[0] = h->h_name ? copy_string(h->h_name) : nullptr;
 
 	for ( num_addrs = 0; h->h_addr_list[num_addrs]; ++num_addrs )
 		;
@@ -344,7 +344,7 @@ void DNS_Mapping::Init(struct hostent* h)
 				                  IPAddr::Network);
 		}
 	else
-		addrs = 0;
+		addrs = nullptr;
 
 	failed = false;
 	}
@@ -352,10 +352,10 @@ void DNS_Mapping::Init(struct hostent* h)
 void DNS_Mapping::Clear()
 	{
 	num_names = num_addrs = 0;
-	names = 0;
-	addrs = 0;
-	host_val = 0;
-	addrs_val = 0;
+	names = nullptr;
+	addrs = nullptr;
+	host_val = nullptr;
+	addrs_val = nullptr;
 	no_mapping = false;
 	map_type = 0;
 	failed = true;
@@ -363,7 +363,7 @@ void DNS_Mapping::Clear()
 
 void DNS_Mapping::Save(FILE* f) const
 	{
-	fprintf(f, "%.0f %d %s %d %s %d %d %" PRIu32"\n", creation_time, req_host != 0,
+	fprintf(f, "%.0f %d %s %d %s %d %d %" PRIu32"\n", creation_time, req_host != nullptr,
 		req_host ? req_host : req_addr.AsString().c_str(),
 		failed, (names && names[0]) ? names[0] : "*",
 		map_type, num_addrs, req_ttl);
@@ -381,11 +381,11 @@ DNS_Mgr::DNS_Mgr(DNS_MgrMode arg_mode)
 
 	dns_mapping_valid = dns_mapping_unverified = dns_mapping_new_name =
 		dns_mapping_lost_name = dns_mapping_name_changed =
-			dns_mapping_altered =  0;
+			dns_mapping_altered =  nullptr;
 
-	dm_rec = 0;
+	dm_rec = nullptr;
 
-	cache_name = dir = 0;
+	cache_name = dir = nullptr;
 
 	asyncs_pending = 0;
 	num_requests = 0;
@@ -540,7 +540,7 @@ IntrusivePtr<TableVal> DNS_Mgr::LookupHost(const char* name)
 
 	case DNS_FORCE:
 		reporter->FatalError("can't find DNS entry for %s in cache", name);
-		return 0;
+		return nullptr;
 
 	case DNS_DEFAULT:
 		requests.push_back(new DNS_Mgr_Request(name, AF_INET, false));
@@ -550,7 +550,7 @@ IntrusivePtr<TableVal> DNS_Mgr::LookupHost(const char* name)
 
 	default:
 		reporter->InternalError("bad mode in DNS_Mgr::LookupHost");
-		return 0;
+		return nullptr;
 	}
 	}
 
@@ -585,7 +585,7 @@ IntrusivePtr<Val> DNS_Mgr::LookupAddr(const IPAddr& addr)
 	case DNS_FORCE:
 		reporter->FatalError("can't find DNS entry for %s in cache",
 		    addr.AsString().c_str());
-		return 0;
+		return nullptr;
 
 	case DNS_DEFAULT:
 		requests.push_back(new DNS_Mgr_Request(addr));
@@ -594,7 +594,7 @@ IntrusivePtr<Val> DNS_Mgr::LookupAddr(const IPAddr& addr)
 
 	default:
 		reporter->InternalError("bad mode in DNS_Mgr::LookupAddr");
-		return 0;
+		return nullptr;
 	}
 	}
 
@@ -634,7 +634,7 @@ void DNS_Mgr::Resolve()
 				DNS_Mgr_Request* dr = requests[i];
 				if ( dr->RequestPending() )
 					{
-					AddResult(dr, 0);
+					AddResult(dr, nullptr);
 					dr->RequestDone();
 					}
 				}
@@ -748,7 +748,7 @@ IntrusivePtr<Val> DNS_Mgr::BuildMappingVal(DNS_Mapping* dm)
 
 void DNS_Mgr::AddResult(DNS_Mgr_Request* dr, struct nb_dns_result* r)
 	{
-	struct hostent* h = (r && r->host_errno == 0) ? r->hostent : 0;
+	struct hostent* h = (r && r->host_errno == 0) ? r->hostent : nullptr;
 	u_int32_t ttl = (r && r->host_errno == 0) ? r->ttl : 0;
 
 	DNS_Mapping* new_dm;
@@ -758,7 +758,7 @@ void DNS_Mgr::AddResult(DNS_Mgr_Request* dr, struct nb_dns_result* r)
 	if ( dr->ReqHost() )
 		{
 		new_dm = new DNS_Mapping(dr->ReqHost(), h, ttl);
-		prev_dm = 0;
+		prev_dm = nullptr;
 
 		if ( dr->ReqIsTxt() )
 			{
@@ -784,10 +784,10 @@ void DNS_Mgr::AddResult(DNS_Mgr_Request* dr, struct nb_dns_result* r)
 			if ( it == host_mappings.end() )
 				{
 				host_mappings[dr->ReqHost()].first =
-					new_dm->Type() == AF_INET ? new_dm : 0;
+					new_dm->Type() == AF_INET ? new_dm : nullptr;
 
 				host_mappings[dr->ReqHost()].second =
-					new_dm->Type() == AF_INET ? 0 : new_dm;
+					new_dm->Type() == AF_INET ? nullptr : new_dm;
 				}
 			else
 				{
@@ -980,7 +980,7 @@ const char* DNS_Mgr::LookupAddrInCache(const IPAddr& addr)
 	AddrMap::iterator it = addr_mappings.find(addr);
 
 	if ( it == addr_mappings.end() )
-		return 0;
+		return nullptr;
 
 	DNS_Mapping* d = it->second;
 
@@ -988,7 +988,7 @@ const char* DNS_Mgr::LookupAddrInCache(const IPAddr& addr)
 		{
 		addr_mappings.erase(it);
 		delete d;
-		return 0;
+		return nullptr;
 		}
 
 	// The escapes in the following strings are to avoid having it
@@ -1002,21 +1002,21 @@ IntrusivePtr<TableVal> DNS_Mgr::LookupNameInCache(const string& name)
 	if ( it == host_mappings.end() )
 		{
 		it = host_mappings.begin();
-		return 0;
+		return nullptr;
 		}
 
 	DNS_Mapping* d4 = it->second.first;
 	DNS_Mapping* d6 = it->second.second;
 
 	if ( ! d4 || ! d4->names || ! d6 || ! d6->names )
-		return 0;
+		return nullptr;
 
 	if ( d4->Expired() || d6->Expired() )
 		{
 		host_mappings.erase(it);
 		delete d4;
 		delete d6;
-		return 0;
+		return nullptr;
 		}
 
 	auto tv4 = d4->AddrsSet();
@@ -1029,7 +1029,7 @@ const char* DNS_Mgr::LookupTextInCache(const string& name)
 	{
 	TextMap::iterator it = text_mappings.find(name);
 	if ( it == text_mappings.end() )
-		return 0;
+		return nullptr;
 
 	DNS_Mapping* d = it->second;
 
@@ -1037,7 +1037,7 @@ const char* DNS_Mgr::LookupTextInCache(const string& name)
 		{
 		text_mappings.erase(it);
 		delete d;
-		return 0;
+		return nullptr;
 		}
 
 	// The escapes in the following strings are to avoid having it
@@ -1077,7 +1077,7 @@ void DNS_Mgr::AsyncLookupAddr(const IPAddr& host, LookupCallback* callback)
 		return;
 		}
 
-	AsyncRequest* req = 0;
+	AsyncRequest* req = nullptr;
 
 	// Have we already a request waiting for this host?
 	AsyncRequestAddrMap::iterator i = asyncs_addrs.find(host);
@@ -1115,7 +1115,7 @@ void DNS_Mgr::AsyncLookupName(const string& name, LookupCallback* callback)
 		return;
 		}
 
-	AsyncRequest* req = 0;
+	AsyncRequest* req = nullptr;
 
 	// Have we already a request waiting for this host?
 	AsyncRequestNameMap::iterator i = asyncs_names.find(name);
@@ -1154,7 +1154,7 @@ void DNS_Mgr::AsyncLookupNameText(const string& name, LookupCallback* callback)
 		return;
 		}
 
-	AsyncRequest* req = 0;
+	AsyncRequest* req = nullptr;
 
 	// Have we already a request waiting for this host?
 	AsyncRequestTextMap::iterator i = asyncs_texts.find(name);
diff --git a/src/DbgBreakpoint.cc b/src/DbgBreakpoint.cc
index aeb9ed0487..60c67f887d 100644
--- a/src/DbgBreakpoint.cc
+++ b/src/DbgBreakpoint.cc
@@ -49,13 +49,13 @@ DbgBreakpoint::DbgBreakpoint()
 	enabled = temporary = false;
 	BPID = -1;
 
-	at_stmt = 0;
+	at_stmt = nullptr;
 	at_time = -1.0;
 
 	repeat_count = hit_count = 0;
 
 	description[0] = 0;
-	source_filename = 0;
+	source_filename = nullptr;
 	source_line = 0;
 	}
 
diff --git a/src/Debug.cc b/src/Debug.cc
index 7bc6e3f4bb..3a13a4c7f7 100644
--- a/src/Debug.cc
+++ b/src/Debug.cc
@@ -55,7 +55,7 @@ DebuggerState::DebuggerState()
 	BreakFromSignal(false);
 
 	// ### Don't choose this arbitrary size! Extend Frame.
-	dbg_locals = new Frame(1024, /* func = */ 0, /* fn_args = */ 0);
+	dbg_locals = new Frame(1024, /* func = */ nullptr, /* fn_args = */ nullptr);
 	}
 
 DebuggerState::~DebuggerState()
@@ -107,7 +107,7 @@ FILE* TraceState::SetTraceFile(const char* filename)
 	else
 		{
 		fprintf(stderr, "Unable to open trace file %s\n", filename);
-		trace_file = 0;
+		trace_file = nullptr;
 		}
 
 	return oldfile;
@@ -137,7 +137,7 @@ int TraceState::LogTrace(const char* fmt, ...)
 
 	const Stmt* stmt;
 	Location loc;
-	loc.filename = 0;
+	loc.filename = nullptr;
 
 	if ( g_frame_stack.size() > 0 && g_frame_stack.back() )
 		{
@@ -178,7 +178,7 @@ void get_first_statement(Stmt* list, Stmt*& first, Location& loc)
 	{
 	if ( ! list )
 		{
-		first = 0;
+		first = nullptr;
 		return;
 		}
 
@@ -231,7 +231,7 @@ static void parse_function_name(vector<ParseLocationRec>& result,
 		return;
 		}
 
-	Stmt* body = 0;	// the particular body we care about; 0 = all
+	Stmt* body = nullptr;	// the particular body we care about; 0 = all
 
 	if ( bodies.size() == 1 )
 		body = bodies[0].stmts.get();
@@ -380,7 +380,7 @@ vector<ParseLocationRec> parse_location_string(const string& s)
 			return result;
 			}
 
-		StmtLocMapping* hit = 0;
+		StmtLocMapping* hit = nullptr;
 		for ( const auto entry : *(iter->second) )
 			{
 			plr.filename = entry->Loc().filename;
@@ -399,7 +399,7 @@ vector<ParseLocationRec> parse_location_string(const string& s)
 		if ( hit )
 			plr.stmt = hit->Statement();
 		else
-			plr.stmt = 0;
+			plr.stmt = nullptr;
 		}
 
 	return result;
@@ -730,7 +730,7 @@ static char* get_prompt(bool reset_counter = false)
 string get_context_description(const Stmt* stmt, const Frame* frame)
 	{
 	ODesc d;
-	const BroFunc* func = frame ? frame->GetFunction() : 0;
+	const BroFunc* func = frame ? frame->GetFunction() : nullptr;
 
 	if ( func )
 		func->DescribeDebug(&d, frame->GetFuncArgs());
@@ -758,7 +758,7 @@ string get_context_description(const Stmt* stmt, const Frame* frame)
 
 int dbg_handle_debug_input()
 	{
-	static char* input_line = 0;
+	static char* input_line = nullptr;
 	int status = 0;
 
 	if ( g_debugger_state.BreakFromSignal() )
@@ -820,7 +820,7 @@ int dbg_handle_debug_input()
 		if ( input_line )
 			{
 			free(input_line);	// this was malloc'ed
-			input_line = 0;
+			input_line = nullptr;
 			}
 		else
 			exit(0);
@@ -934,8 +934,8 @@ bool post_execute_stmt(Stmt* stmt, Frame* f, Val* result, stmt_flow_type* flow)
 
 // Evaluates the given expression in the context of the currently selected
 // frame.  Returns the resulting value, or nil if none (or there was an error).
-Expr* g_curr_debug_expr = 0;
-const char* g_curr_debug_error = 0;
+Expr* g_curr_debug_expr = nullptr;
+const char* g_curr_debug_error = nullptr;
 bool in_debug = false;
 
 // ### fix this hardwired access to external variables etc.
@@ -993,7 +993,7 @@ IntrusivePtr<Val> dbg_eval_expr(const char* expr)
 		if ( g_curr_debug_expr )
 			{
 			delete g_curr_debug_expr;
-			g_curr_debug_expr = 0;
+			g_curr_debug_expr = nullptr;
 			}
 		}
 	else
@@ -1003,9 +1003,9 @@ IntrusivePtr<Val> dbg_eval_expr(const char* expr)
 		pop_scope();
 
 	delete g_curr_debug_expr;
-	g_curr_debug_expr = 0;
+	g_curr_debug_expr = nullptr;
 	delete [] g_curr_debug_error;
-	g_curr_debug_error = 0;
+	g_curr_debug_error = nullptr;
 	in_debug = false;
 
 	return result;
diff --git a/src/Debug.h b/src/Debug.h
index ae3114ebc4..5208e61780 100644
--- a/src/Debug.h
+++ b/src/Debug.h
@@ -149,7 +149,7 @@ bool post_execute_stmt(Stmt* stmt, Frame* f, Val* result, stmt_flow_type* flow);
 // Returns 1 if successful, 0 otherwise.
 // If cmdfile is non-nil, it contains the location of a file of commands
 // to be executed as debug commands.
-int dbg_init_debugger(const char* cmdfile = 0);
+int dbg_init_debugger(const char* cmdfile = nullptr);
 int dbg_shutdown_debugger();
 
 // Returns 1 if successful, 0 otherwise.
diff --git a/src/DebugCmds.cc b/src/DebugCmds.cc
index b65d979f5e..eb284a6c69 100644
--- a/src/DebugCmds.cc
+++ b/src/DebugCmds.cc
@@ -125,7 +125,7 @@ void choose_global_symbols_regex(const string& regex, vector<ID*>& choices,
 PQueue<DebugCmdInfo> g_DebugCmdInfos;
 
 DebugCmdInfo::DebugCmdInfo(const DebugCmdInfo& info)
-: cmd(info.cmd), helpstring(0)
+: cmd(info.cmd), helpstring(nullptr)
 	{
 	num_names = info.num_names;
 	names = info.names;
@@ -153,7 +153,7 @@ const DebugCmdInfo* get_debug_cmd_info(DebugCmd cmd)
 	if ( (int) cmd < g_DebugCmdInfos.length() )
 		return g_DebugCmdInfos[(int) cmd];
 	else
-		return 0;
+		return nullptr;
 	}
 
 int find_all_matching_cmds(const string& prefix, const char* array_of_matches[])
@@ -165,7 +165,7 @@ int find_all_matching_cmds(const string& prefix, const char* array_of_matches[])
 
 	for ( int i = 0; i < num_debug_cmds(); ++i )
 		{
-		array_of_matches[g_DebugCmdInfos[i]->Cmd()] = 0;
+		array_of_matches[g_DebugCmdInfos[i]->Cmd()] = nullptr;
 
 		for ( int j = 0; j < g_DebugCmdInfos[i]->NumNames(); ++j )
 			{
@@ -177,7 +177,7 @@ int find_all_matching_cmds(const string& prefix, const char* array_of_matches[])
 			if ( ! prefix.compare(curr_name) )
 				{
 				for ( int k = 0; k < num_debug_cmds(); ++k )
-					array_of_matches[k] = 0;
+					array_of_matches[k] = nullptr;
 
 				array_of_matches[g_DebugCmdInfos[i]->Cmd()] = curr_name;
 				return 1;
@@ -214,7 +214,7 @@ static int dbg_backtrace_internal(int start, int end)
 	for ( int i = start; i >= end; --i )
 		{
 		const Frame* f = g_frame_stack[i];
-		const Stmt* stmt = f ? f->GetNextStmt() : 0;
+		const Stmt* stmt = f ? f->GetNextStmt() : nullptr;
 
 		string context = get_context_description(stmt, f);
 		debug_msg("#%d  %s\n",
diff --git a/src/DebugCmds.h b/src/DebugCmds.h
index 2e4e424888..ff318140e0 100644
--- a/src/DebugCmds.h
+++ b/src/DebugCmds.h
@@ -18,7 +18,7 @@ public:
 			bool resume_execution, const char* const helpstring,
 			bool repeatable);
 
-	DebugCmdInfo() : helpstring(0) {}
+	DebugCmdInfo() : helpstring(nullptr) {}
 
 	int Cmd() const		{ return cmd; }
 	int NumNames() const	{ return num_names; }
diff --git a/src/DebugLogger.cc b/src/DebugLogger.cc
index fdb57efc61..4fac89414e 100644
--- a/src/DebugLogger.cc
+++ b/src/DebugLogger.cc
@@ -26,7 +26,7 @@ DebugLogger::Stream DebugLogger::streams[NUM_DBGS] = {
 DebugLogger::DebugLogger()
 	{
 	verbose = false;
-	file = 0;
+	file = nullptr;
 	}
 
 DebugLogger::~DebugLogger()
diff --git a/src/Desc.cc b/src/Desc.cc
index 50d95f80c8..c02347f42f 100644
--- a/src/Desc.cc
+++ b/src/Desc.cc
@@ -21,7 +21,7 @@ ODesc::ODesc(desc_type t, BroFile* arg_f)
 	style = STANDARD_STYLE;
 	f = arg_f;
 
-	if ( f == 0 )
+	if ( f == nullptr )
 		{
 		size = DEFAULT_SIZE;
 		base = safe_malloc(size);
@@ -31,7 +31,7 @@ ODesc::ODesc(desc_type t, BroFile* arg_f)
 	else
 		{
 		offset = size = 0;
-		base = 0;
+		base = nullptr;
 		}
 
 	indent_level = 0;
diff --git a/src/Desc.h b/src/Desc.h
index bbb365abd5..658f0c477e 100644
--- a/src/Desc.h
+++ b/src/Desc.h
@@ -29,7 +29,7 @@ class BroType;
 
 class ODesc {
 public:
-	explicit ODesc(desc_type t=DESC_READABLE, BroFile* f=0);
+	explicit ODesc(desc_type t=DESC_READABLE, BroFile* f=nullptr);
 
 	~ODesc();
 
@@ -131,7 +131,7 @@ public:
 	byte_vec TakeBytes()
 		{
 		const void* t = base;
-		base = 0;
+		base = nullptr;
 		size = 0;
 
 		// Don't clear offset, as we want to still support
diff --git a/src/Dict.cc b/src/Dict.cc
index 369510f7b1..1f62908c5c 100644
--- a/src/Dict.cc
+++ b/src/Dict.cc
@@ -81,7 +81,7 @@ TEST_CASE("dict operation")
 	dict.Remove(key2);
 	CHECK(dict.Length() == 0);
 	uint32_t* lookup2 = dict.Lookup(key2);
-	CHECK(lookup2 == (uint32_t*)0);
+	CHECK(lookup2 == (uint32_t*)nullptr);
 	delete key2;
 
 	CHECK(dict.MaxLength() == 1);
@@ -132,7 +132,7 @@ TEST_CASE("dict nthentry")
 
 	// NthEntry returns null for unordered dicts
 	uint32_t* lookup = unordered.NthEntry(0);
-	CHECK(lookup == (uint32_t*)0);
+	CHECK(lookup == (uint32_t*)nullptr);
 
 	// Ordered dicts are based on order of insertion, nothing about the
 	// data itself
@@ -256,7 +256,7 @@ void Dictionary::DeInit()
 void* Dictionary::Lookup(const void* key, int key_size, hash_t hash) const
 	{
 	if ( ! tbl && ! tbl2 )
-		return 0;
+		return nullptr;
 
 	hash_t h;
 	PList<DictEntry>* chain;
@@ -280,7 +280,7 @@ void* Dictionary::Lookup(const void* key, int key_size, hash_t hash) const
 			}
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 void* Dictionary::Insert(void* key, int key_size, hash_t hash, void* val,
@@ -314,7 +314,7 @@ void* Dictionary::Remove(const void* key, int key_size, hash_t hash,
 				bool dont_delete)
 	{
 	if ( ! tbl && ! tbl2 )
-		return 0;
+		return nullptr;
 
 	hash_t h;
 	PList<DictEntry>* chain;
@@ -334,7 +334,7 @@ void* Dictionary::Remove(const void* key, int key_size, hash_t hash,
 		}
 
 	if ( ! chain )
-		return 0;
+		return nullptr;
 
 	for ( int i = 0; i < chain->length(); ++i )
 		{
@@ -346,7 +346,7 @@ void* Dictionary::Remove(const void* key, int key_size, hash_t hash,
 			void* entry_value = DoRemove(entry, h, chain, i);
 
 			if ( dont_delete )
-				entry->key = 0;
+				entry->key = nullptr;
 
 			delete entry;
 			--*num_entries_ptr;
@@ -354,7 +354,7 @@ void* Dictionary::Remove(const void* key, int key_size, hash_t hash,
 			}
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 void* Dictionary::DoRemove(DictEntry* entry, hash_t h,
@@ -395,7 +395,7 @@ void* Dictionary::DoRemove(DictEntry* entry, hash_t h,
 void* Dictionary::NthEntry(int n, const void*& key, int& key_len) const
 	{
 	if ( ! order || n < 0 || n >= Length() )
-		return 0;
+		return nullptr;
 
 	DictEntry* entry = (*order)[n];
 	key = entry->key;
@@ -419,8 +419,8 @@ void* Dictionary::NextEntry(HashKey*& h, IterCookie*& cookie, int return_hash) c
 		{
 		const_cast<PList<IterCookie>*>(&cookies)->remove(cookie);
 		delete cookie;
-		cookie = 0;
-		return 0;
+		cookie = nullptr;
+		return nullptr;
 		}
 
 	// If there are any inserted entries, return them first.
@@ -486,8 +486,8 @@ void* Dictionary::NextEntry(HashKey*& h, IterCookie*& cookie, int return_hash) c
 		// a better way?
 		const_cast<PList<IterCookie>*>(&cookies)->remove(cookie);
 		delete cookie;
-		cookie = 0;
-		return 0;
+		cookie = nullptr;
+		return nullptr;
 		}
 
 	entry = (*ttbl[b])[0];
@@ -604,7 +604,7 @@ void* Dictionary::Insert(DictEntry* new_entry, bool copy_key)
 			c->inserted.push_back(new_entry);
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 int Dictionary::NextPrime(int n) const
@@ -665,7 +665,7 @@ void Dictionary::MoveChains()
 		if ( ! chain )
 			continue;
 
-		tbl[tbl_next_ind - 1] = 0;
+		tbl[tbl_next_ind - 1] = nullptr;
 
 		for ( int j = 0; j < chain->length(); ++j )
 			{
diff --git a/src/Dict.h b/src/Dict.h
index 48e538c3af..d4187aa01f 100644
--- a/src/Dict.h
+++ b/src/Dict.h
@@ -70,7 +70,7 @@ public:
 		}
 
 	// True if the dictionary is ordered, false otherwise.
-	bool IsOrdered() const		{ return order != 0; }
+	bool IsOrdered() const		{ return order != nullptr; }
 
 	// If the dictionary is ordered then returns the n'th entry's value;
 	// the second method also returns the key.  The first entry inserted
diff --git a/src/EquivClass.cc b/src/EquivClass.cc
index c067137227..39bc2699c2 100644
--- a/src/EquivClass.cc
+++ b/src/EquivClass.cc
@@ -12,7 +12,7 @@ EquivClass::EquivClass(int arg_size)
 	bck = new int[size];
 	equiv_class = new int[size];
 	rep = new int[size];
-	ccl_flags = 0;
+	ccl_flags = nullptr;
 	num_ecs = 0;
 
 	ec_nil = no_class = no_rep = size + 1;
diff --git a/src/Event.cc b/src/Event.cc
index c33fba5929..11e34b0117 100644
--- a/src/Event.cc
+++ b/src/Event.cc
@@ -74,10 +74,10 @@ void Event::Dispatch(bool no_remote)
 
 EventMgr::EventMgr()
 	{
-	head = tail = 0;
+	head = tail = nullptr;
 	current_src = SOURCE_LOCAL;
 	current_aid = 0;
-	src_val = 0;
+	src_val = nullptr;
 	draining = false;
 	}
 
@@ -176,8 +176,8 @@ void EventMgr::Drain()
 	for ( int round = 0; head && round < 2; round++ )
 		{
 		Event* current = head;
-		head = 0;
-		tail = 0;
+		head = nullptr;
+		tail = nullptr;
 
 		while ( current )
 			{
diff --git a/src/Event.h b/src/Event.h
index a4bedda6d0..fe5dc9baf2 100644
--- a/src/Event.h
+++ b/src/Event.h
@@ -64,7 +64,7 @@ public:
 	[[deprecated("Remove in v4.1.  Use Enqueue() instead.")]]
 	void QueueEventFast(const EventHandlerPtr &h, val_list vl,
 			SourceID src = SOURCE_LOCAL, analyzer::ID aid = 0,
-			TimerMgr* mgr = 0, BroObj* obj = 0);
+			TimerMgr* mgr = nullptr, BroObj* obj = nullptr);
 
 	// Queues an event if there's an event handler (or remote consumer).  This
 	// function always takes ownership of decrementing the reference count of
@@ -75,7 +75,7 @@ public:
 	[[deprecated("Remove in v4.1.  Use Enqueue() instead.")]]
 	void QueueEvent(const EventHandlerPtr &h, val_list vl,
 			SourceID src = SOURCE_LOCAL, analyzer::ID aid = 0,
-			TimerMgr* mgr = 0, BroObj* obj = 0);
+			TimerMgr* mgr = nullptr, BroObj* obj = nullptr);
 
 	// Same as QueueEvent, except taking the event's argument list via a
 	// pointer instead of by value.  This function takes ownership of the
@@ -84,7 +84,7 @@ public:
 	[[deprecated("Remove in v4.1.  Use Enqueue() instead.")]]
 	void QueueEvent(const EventHandlerPtr &h, val_list* vl,
 			SourceID src = SOURCE_LOCAL, analyzer::ID aid = 0,
-			TimerMgr* mgr = 0, BroObj* obj = 0);
+			TimerMgr* mgr = nullptr, BroObj* obj = nullptr);
 
 	/**
 	 * Adds an event to the queue.  If no handler is found for the event
@@ -117,7 +117,7 @@ public:
 	void Drain();
 	bool IsDraining() const	{ return draining; }
 
-	bool HasEvents() const	{ return head != 0; }
+	bool HasEvents() const	{ return head != nullptr; }
 
 	// Returns the source ID of last raised event.
 	SourceID CurrentSource() const	{ return current_src; }
diff --git a/src/EventHandler.cc b/src/EventHandler.cc
index 8f35d47ed5..c1fad45a91 100644
--- a/src/EventHandler.cc
+++ b/src/EventHandler.cc
@@ -13,8 +13,8 @@ EventHandler::EventHandler(const char* arg_name)
 	{
 	name = copy_string(arg_name);
 	used = false;
-	local = 0;
-	type = 0;
+	local = nullptr;
+	type = nullptr;
 	error_handler = false;
 	enabled = true;
 	generate_always = false;
@@ -42,10 +42,10 @@ FuncType* EventHandler::FType(bool check_export)
 	                    check_export);
 
 	if ( ! id )
-		return 0;
+		return nullptr;
 
 	if ( id->Type()->Tag() != TYPE_FUNC )
-		return 0;
+		return nullptr;
 
 	type = id->Type()->AsFuncType();
 	return type;
diff --git a/src/EventHandler.h b/src/EventHandler.h
index effafb134e..59773560f6 100644
--- a/src/EventHandler.h
+++ b/src/EventHandler.h
@@ -69,7 +69,7 @@ private:
 // Encapsulates a ptr to an event handler to overload the boolean operator.
 class EventHandlerPtr {
 public:
-	EventHandlerPtr(EventHandler* p = 0)		{ handler = p; }
+	EventHandlerPtr(EventHandler* p = nullptr)		{ handler = p; }
 	EventHandlerPtr(const EventHandlerPtr& h)	{ handler = h.handler; }
 
 	const EventHandlerPtr& operator=(EventHandler* p)
diff --git a/src/Expr.cc b/src/Expr.cc
index 0c99f01012..cb34859ea6 100644
--- a/src/Expr.cc
+++ b/src/Expr.cc
@@ -54,7 +54,7 @@ const char* expr_name(BroExprTag t)
 	return expr_names[int(t)];
 	}
 
-Expr::Expr(BroExprTag arg_tag) : tag(arg_tag), type(0), paren(false)
+Expr::Expr(BroExprTag arg_tag) : tag(arg_tag), type(nullptr), paren(false)
 	{
 	SetLocationInfo(&start_location, &end_location);
 	}
@@ -1623,7 +1623,7 @@ IntrusivePtr<Val> BoolExpr::Eval(Frame* f) const
 			result->Assign(i, val_mgr->GetBool(local_result));
 			}
 		else
-			result->Assign(i, 0);
+			result->Assign(i, nullptr);
 		}
 
 	return result;
@@ -1952,7 +1952,7 @@ IntrusivePtr<Val> CondExpr::Eval(Frame* f) const
 			result->Assign(i, v ? v->Ref() : nullptr);
 			}
 		else
-			result->Assign(i, 0);
+			result->Assign(i, nullptr);
 		}
 
 	return result;
@@ -2019,7 +2019,7 @@ AssignExpr::AssignExpr(IntrusivePtr<Expr> arg_op1, IntrusivePtr<Expr> arg_op2,
 	             std::move(arg_op1) : arg_op1->MakeLvalue(),
 	             std::move(arg_op2))
 	{
-	val = 0;
+	val = nullptr;
 	is_init = arg_is_init;
 
 	if ( IsError() )
@@ -2079,7 +2079,7 @@ bool AssignExpr::TypeCheck(attr_list* attrs)
 
 	if ( bt1 == TYPE_TABLE && op2->Tag() == EXPR_LIST )
 		{
-		attr_list* attr_copy = 0;
+		attr_list* attr_copy = nullptr;
 
 		if ( attrs )
 			{
@@ -2178,7 +2178,7 @@ bool AssignExpr::TypeCheck(attr_list* attrs)
 					return false;
 					}
 
-				attr_list* attr_copy = 0;
+				attr_list* attr_copy = nullptr;
 
 				if ( sce->Attrs() )
 					{
@@ -2293,7 +2293,7 @@ void AssignExpr::EvalIntoAggregate(const BroType* t, Val* aggr, Frame* f) const
 	if ( IsError() )
 		return;
 
-	TypeDecl td(0, 0);
+	TypeDecl td(nullptr, nullptr);
 
 	if ( IsRecordElement(&td) )
 		{
@@ -2348,7 +2348,7 @@ IntrusivePtr<Val> AssignExpr::InitVal(const BroType* t, IntrusivePtr<Val> aggr)
 	if ( IsError() )
 		return nullptr;
 
-	TypeDecl td(0, 0);
+	TypeDecl td(nullptr, nullptr);
 
 	if ( IsRecordElement(&td) )
 		{
@@ -2690,7 +2690,7 @@ IntrusivePtr<Val> IndexExpr::Fold(Val* v1, Val* v2) const
 		const ListVal* lv = v2->AsListVal();
 		const BroString* s = v1->AsString();
 		int len = s->Len();
-		BroString* substring = 0;
+		BroString* substring = nullptr;
 
 		if ( lv->Length() == 1 )
 			{
@@ -2709,7 +2709,7 @@ IntrusivePtr<Val> IndexExpr::Fold(Val* v1, Val* v2) const
 			bro_int_t substring_len = last - first;
 
 			if ( substring_len < 0 )
-				substring = 0;
+				substring = nullptr;
 			else
 				substring = s->GetSubstring(first, substring_len);
 			}
@@ -2851,7 +2851,7 @@ TraversalCode IndexExpr::Traverse(TraversalCallback* cb) const
 
 FieldExpr::FieldExpr(IntrusivePtr<Expr> arg_op, const char* arg_field_name)
 	: UnaryExpr(EXPR_FIELD, std::move(arg_op)),
-	  field_name(copy_string(arg_field_name)), td(0), field(0)
+	  field_name(copy_string(arg_field_name)), td(nullptr), field(0)
 	{
 	if ( IsError() )
 		return;
@@ -2905,7 +2905,7 @@ void FieldExpr::Assign(Frame* f, IntrusivePtr<Val> v)
 
 void FieldExpr::Delete(Frame* f)
 	{
-	Assign(f, 0);
+	Assign(f, nullptr);
 	}
 
 IntrusivePtr<Val> FieldExpr::Fold(Val* v) const
@@ -2914,7 +2914,7 @@ IntrusivePtr<Val> FieldExpr::Fold(Val* v) const
 		return {NewRef{}, result};
 
 	// Check for &default.
-	const Attr* def_attr = td ? td->FindAttr(ATTR_DEFAULT) : 0;
+	const Attr* def_attr = td ? td->FindAttr(ATTR_DEFAULT) : nullptr;
 
 	if ( def_attr )
 		return def_attr->AttrExpr()->Eval(nullptr);
@@ -3101,7 +3101,7 @@ TableConstructorExpr::TableConstructorExpr(IntrusivePtr<ListExpr> constructor_li
 			}
 		}
 
-	attrs = arg_attrs ? new Attributes(arg_attrs, type, false, false) : 0;
+	attrs = arg_attrs ? new Attributes(arg_attrs, type, false, false) : nullptr;
 
 	type_list* indices = type->AsTableType()->Indices()->Types();
 	const expr_list& cle = op->AsListExpr()->Exprs();
@@ -3173,7 +3173,7 @@ IntrusivePtr<Val> TableConstructorExpr::InitVal(const BroType* t, IntrusivePtr<V
 	const expr_list& exprs = op->AsListExpr()->Exprs();
 
 	for ( const auto& expr : exprs )
-		expr->EvalIntoAggregate(t, tval.get(), 0);
+		expr->EvalIntoAggregate(t, tval.get(), nullptr);
 
 	return tval;
 	}
@@ -3219,7 +3219,7 @@ SetConstructorExpr::SetConstructorExpr(IntrusivePtr<ListExpr> constructor_list,
 	else if ( type->Tag() != TYPE_TABLE || ! type->AsTableType()->IsSet() )
 		SetError("values in set(...) constructor do not specify a set");
 
-	attrs = arg_attrs ? new Attributes(arg_attrs, type, false, false) : 0;
+	attrs = arg_attrs ? new Attributes(arg_attrs, type, false, false) : nullptr;
 
 	type_list* indices = type->AsTableType()->Indices()->Types();
 	expr_list& cle = op->AsListExpr()->Exprs();
@@ -3265,7 +3265,7 @@ IntrusivePtr<Val> SetConstructorExpr::Eval(Frame* f) const
 	for ( const auto& expr : exprs )
 		{
 		auto element = expr->Eval(f);
-		aggr->Assign(element.get(), 0);
+		aggr->Assign(element.get(), nullptr);
 		}
 
 	return aggr;
@@ -3287,7 +3287,7 @@ IntrusivePtr<Val> SetConstructorExpr::InitVal(const BroType* t, IntrusivePtr<Val
 		{
 		auto element = check_and_promote(e->Eval(nullptr), index_type, true);
 
-		if ( ! element || ! tval->Assign(element.get(), 0) )
+		if ( ! element || ! tval->Assign(element.get(), nullptr) )
 			{
 			Error(fmt("initialization type mismatch in set"), e);
 			return nullptr;
@@ -3521,7 +3521,7 @@ IntrusivePtr<Val> ArithCoerceExpr::Fold(Val* v) const
 		if ( Val* elt = vv->Lookup(i) )
 			result->Assign(i, FoldSingleVal(elt, t));
 		else
-			result->Assign(i, 0);
+			result->Assign(i, nullptr);
 		}
 
 	return result;
@@ -4191,7 +4191,7 @@ IntrusivePtr<Val> CallExpr::Eval(Frame* f) const
 	if ( func_val && v )
 		{
 		const ::Func* funcv = func_val->AsFunc();
-		const CallExpr* current_call = f ? f->GetCall() : 0;
+		const CallExpr* current_call = f ? f->GetCall() : nullptr;
 
 		if ( f )
 			f->SetCall(this);
@@ -4491,12 +4491,12 @@ IntrusivePtr<BroType> ListExpr::InitType() const
 		return nullptr;
 		}
 
-	if ( exprs[0]->IsRecordElement(0) )
+	if ( exprs[0]->IsRecordElement(nullptr) )
 		{
 		type_decl_list* types = new type_decl_list(exprs.length());
 		for ( const auto& expr : exprs )
 			{
-			TypeDecl* td = new TypeDecl(0, 0);
+			TypeDecl* td = new TypeDecl(nullptr, nullptr);
 			if ( ! expr->IsRecordElement(td) )
 				{
 				expr->Error("record element expected");
@@ -5063,7 +5063,7 @@ bool check_and_promote_args(ListExpr* const args, RecordType* types)
 		for ( int i = ntypes - 1; i >= el.length(); --i )
 			{
 			TypeDecl* td = types->FieldDecl(i);
-			Attr* def_attr = td->attrs ? td->attrs->FindAttr(ATTR_DEFAULT) : 0;
+			Attr* def_attr = td->attrs ? td->attrs->FindAttr(ATTR_DEFAULT) : nullptr;
 
 			if ( ! def_attr )
 				{
diff --git a/src/Expr.h b/src/Expr.h
index 33b3a05b8b..543efa1cee 100644
--- a/src/Expr.h
+++ b/src/Expr.h
@@ -523,7 +523,7 @@ public:
 	bool IsPure() const override;
 
 protected:
-	bool TypeCheck(attr_list* attrs = 0);
+	bool TypeCheck(attr_list* attrs = nullptr);
 	bool TypeCheckArithmetics(TypeTag bt1, TypeTag bt2);
 
 	bool is_init;
diff --git a/src/File.cc b/src/File.cc
index ade6918715..7581b9fb3b 100644
--- a/src/File.cc
+++ b/src/File.cc
@@ -56,9 +56,9 @@ BroFile::BroFile(FILE* arg_f)
 	{
 	Init();
 	f = arg_f;
-	name = access = 0;
+	name = access = nullptr;
 	t = base_type(TYPE_STRING);
-	is_open = (f != 0);
+	is_open = (f != nullptr);
 	}
 
 BroFile::BroFile(FILE* arg_f, const char* arg_name, const char* arg_access)
@@ -68,13 +68,13 @@ BroFile::BroFile(FILE* arg_f, const char* arg_name, const char* arg_access)
 	name = copy_string(arg_name);
 	access = copy_string(arg_access);
 	t = base_type(TYPE_STRING);
-	is_open = (f != 0);
+	is_open = (f != nullptr);
 	}
 
 BroFile::BroFile(const char* arg_name, const char* arg_access)
 	{
 	Init();
-	f = 0;
+	f = nullptr;
 	name = copy_string(arg_name);
 	access = copy_string(arg_access);
 	t = base_type(TYPE_STRING);
@@ -110,7 +110,7 @@ const char* BroFile::Name() const
 	if ( f == stderr )
 		return "/dev/stderr";
 
-	return 0;
+	return nullptr;
 	}
 
 bool BroFile::Open(FILE* file, const char* mode)
@@ -168,7 +168,7 @@ void BroFile::Init()
 	{
 	open_time = 0;
 	is_open = false;
-	attrs = 0;
+	attrs = nullptr;
 	buffered = true;
 	raw_output = false;
 
@@ -185,7 +185,7 @@ FILE* BroFile::File()
 FILE* BroFile::Seek(long new_position)
 	{
 	if ( ! File() )
-		return 0;
+		return nullptr;
 
 	if ( fseek(f, new_position, SEEK_SET) < 0 )
 		reporter->Error("seek failed");
@@ -271,11 +271,11 @@ void BroFile::SetAttrs(Attributes* arg_attrs)
 RecordVal* BroFile::Rotate()
 	{
 	if ( ! is_open )
-		return 0;
+		return nullptr;
 
 	// Do not rotate stdin/stdout/stderr.
 	if ( f == stdin || f == stdout || f == stderr )
-		return 0;
+		return nullptr;
 
 	RecordVal* info = new RecordVal(rotate_info);
 	FILE* newf = rotate_file(name, info);
@@ -283,7 +283,7 @@ RecordVal* BroFile::Rotate()
 	if ( ! newf )
 		{
 		Unref(info);
-		return 0;
+		return nullptr;
 		}
 
 	info->Assign(2, make_intrusive<Val>(open_time, TYPE_TIME));
@@ -291,7 +291,7 @@ RecordVal* BroFile::Rotate()
 	Unlink();
 
  	fclose(f);
-	f = 0;
+	f = nullptr;
 
 	Open(newf);
 	return info;
diff --git a/src/File.h b/src/File.h
index 7f14d2ad73..01409ff742 100644
--- a/src/File.h
+++ b/src/File.h
@@ -80,7 +80,7 @@ protected:
 	 * If file is not given and mode is, the filename will be opened with that
 	 * access mode.
 	 */
-	bool Open(FILE* f = nullptr, const char* mode = 0);
+	bool Open(FILE* f = nullptr, const char* mode = nullptr);
 
 	void Unlink();
 
diff --git a/src/Frag.cc b/src/Frag.cc
index c571a039d5..c155a91f51 100644
--- a/src/Frag.cc
+++ b/src/Frag.cc
@@ -49,7 +49,7 @@ FragReassembler::FragReassembler(NetSessions* arg_s,
 		memcpy(proto_hdr, ip->IP6_Hdr(), proto_hdr_len);
 		}
 
-	reassembled_pkt = 0;
+	reassembled_pkt = nullptr;
 	frag_size = 0;	// flag meaning "not known"
 	next_proto = ip->NextProto();
 
@@ -59,7 +59,7 @@ FragReassembler::FragReassembler(NetSessions* arg_s,
 		timer_mgr->Add(expire_timer);
 		}
 	else
-		expire_timer = 0;
+		expire_timer = nullptr;
 
 	AddFragment(t, ip, pkt);
 	}
@@ -285,7 +285,7 @@ void FragReassembler::BlockInserted(DataBlockMap::const_iterator /* it */)
 		}
 
 	delete reassembled_pkt;
-	reassembled_pkt = 0;
+	reassembled_pkt = nullptr;
 
 	unsigned int version = ((const struct ip*)pkt_start)->ip_v;
 
@@ -318,7 +318,7 @@ void FragReassembler::Expire(double t)
 	{
 	block_list.Clear();
 	expire_timer->ClearReassembler();
-	expire_timer = 0;	// timer manager will delete it
+	expire_timer = nullptr;	// timer manager will delete it
 
 	sessions->Remove(this);
 	}
@@ -329,6 +329,6 @@ void FragReassembler::DeleteTimer()
 		{
 		expire_timer->ClearReassembler();
 		timer_mgr->Cancel(expire_timer);
-		expire_timer = 0;	// timer manager will delete it
+		expire_timer = nullptr;	// timer manager will delete it
 		}
 	}
diff --git a/src/Frag.h b/src/Frag.h
index 49174b5f0a..4ad8b1b3a6 100644
--- a/src/Frag.h
+++ b/src/Frag.h
@@ -32,7 +32,7 @@ public:
 
 	void Expire(double t);
 	void DeleteTimer();
-	void ClearTimer()	{ expire_timer = 0; }
+	void ClearTimer()	{ expire_timer = nullptr; }
 
 	const IP_Hdr* ReassembledPkt()	{ return reassembled_pkt; }
 	const FragReassemblerKey& Key() const	{ return key; }
@@ -63,7 +63,7 @@ public:
 	void Dispatch(double t, bool is_expire) override;
 
 	// Break the association between this timer and its creator.
-	void ClearReassembler()	{ f = 0; }
+	void ClearReassembler()	{ f = nullptr; }
 
 protected:
 	FragReassembler* f;
diff --git a/src/Frame.cc b/src/Frame.cc
index b12f0fb402..9785ce1ccc 100644
--- a/src/Frame.cc
+++ b/src/Frame.cc
@@ -143,7 +143,7 @@ void Frame::Reset(int startIdx)
 	for ( int i = startIdx; i < size; ++i )
 		{
 		UnrefElement(i);
-		frame[i] = 0;
+		frame[i] = nullptr;
 		}
 	}
 
@@ -166,7 +166,7 @@ void Frame::Describe(ODesc* d) const
 
 		for ( int i = 0; i < size; ++i )
 			 {
-			 d->Add(frame[i] != 0);
+			 d->Add(frame[i] != nullptr);
 			 d->SP();
 			 }
 		}
diff --git a/src/Frame.h b/src/Frame.h
index e5ebd22724..8716022d6e 100644
--- a/src/Frame.h
+++ b/src/Frame.h
@@ -217,7 +217,7 @@ public:
 	trigger::Trigger* GetTrigger() const		{ return trigger.get(); }
 
 	void SetCall(const CallExpr* arg_call)	{ call = arg_call; }
-	void ClearCall()			{ call = 0; }
+	void ClearCall()			{ call = nullptr; }
 	const CallExpr* GetCall() const		{ return call; }
 
 	void SetDelayed()	{ delayed = true; }
diff --git a/src/Func.h b/src/Func.h
index fd3872fcba..9c1c816e33 100644
--- a/src/Func.h
+++ b/src/Func.h
@@ -97,7 +97,7 @@ public:
 
 	uint32_t GetUniqueFuncID() const { return unique_id; }
 	static Func* GetFuncPtrByID(uint32_t id)
-		{ return id >= unique_ids.size() ? 0 : unique_ids[id]; }
+		{ return id >= unique_ids.size() ? nullptr : unique_ids[id]; }
 
 protected:
 	Func();
@@ -205,7 +205,7 @@ public:
 	void Describe(ODesc* d) const override;
 
 protected:
-	BuiltinFunc()	{ func = 0; is_pure = 0; }
+	BuiltinFunc()	{ func = nullptr; is_pure = 0; }
 
 	built_in_func func;
 	bool is_pure;
diff --git a/src/ID.cc b/src/ID.cc
index e0caea3b2d..3494d8a175 100644
--- a/src/ID.cc
+++ b/src/ID.cc
@@ -25,7 +25,7 @@ ID::ID(const char* arg_name, IDScope arg_scope, bool arg_is_export)
 	scope = arg_scope;
 	is_export = arg_is_export;
 	is_option = false;
-	val = 0;
+	val = nullptr;
 	is_const = false;
 	is_enum_const = false;
 	is_type = false;
@@ -60,7 +60,7 @@ void ID::ClearVal()
 	if ( ! weak_ref )
 		Unref(val);
 
-	val = 0;
+	val = nullptr;
 	}
 
 void ID::SetVal(IntrusivePtr<Val> v, bool arg_weak_ref)
@@ -147,12 +147,12 @@ void ID::SetVal(IntrusivePtr<Expr> ev, init_class c)
 
 bool ID::IsRedefinable() const
 	{
-	return FindAttr(ATTR_REDEF) != 0;
+	return FindAttr(ATTR_REDEF) != nullptr;
 	}
 
 void ID::SetAttrs(IntrusivePtr<Attributes> a)
 	{
-	attrs = 0;
+	attrs = nullptr;
 	AddAttrs(std::move(a));
 	}
 
@@ -197,12 +197,12 @@ void ID::UpdateValAttrs()
 
 Attr* ID::FindAttr(attr_tag t) const
 	{
-	return attrs ? attrs->FindAttr(t) : 0;
+	return attrs ? attrs->FindAttr(t) : nullptr;
 	}
 
 bool ID::IsDeprecated() const
 	{
-	return FindAttr(ATTR_DEPRECATED) != 0;
+	return FindAttr(ATTR_DEPRECATED) != nullptr;
 	}
 
 void ID::MakeDeprecated(IntrusivePtr<Expr> deprecation)
diff --git a/src/ID.h b/src/ID.h
index 6e43d0b162..3735e7a843 100644
--- a/src/ID.h
+++ b/src/ID.h
@@ -41,8 +41,8 @@ public:
 	const BroType* Type() const	{ return type.get(); }
 
 	void MakeType()			{ is_type = true; }
-	BroType* AsType()		{ return is_type ? Type() : 0; }
-	const BroType* AsType() const	{ return is_type ? Type() : 0; }
+	BroType* AsType()		{ return is_type ? Type() : nullptr; }
+	const BroType* AsType() const	{ return is_type ? Type() : nullptr; }
 
 	// If weak_ref is false, the Val is assumed to be already ref'ed
 	// and will be deref'ed when the ID is deleted.
@@ -57,7 +57,7 @@ public:
 	void SetVal(IntrusivePtr<Val> v, init_class c);
 	void SetVal(IntrusivePtr<Expr> ev, init_class c);
 
-	bool HasVal() const		{ return val != 0; }
+	bool HasVal() const		{ return val != nullptr; }
 	Val* ID_Val()			{ return val; }
 	const Val* ID_Val() const	{ return val; }
 	void ClearVal();
@@ -90,7 +90,7 @@ public:
 
 	std::string GetDeprecationWarning() const;
 
-	void Error(const char* msg, const BroObj* o2 = 0);
+	void Error(const char* msg, const BroObj* o2 = nullptr);
 
 	void Describe(ODesc* d) const override;
 	// Adds type and value to description.
diff --git a/src/IP.cc b/src/IP.cc
index 65c34c8e40..019bec0790 100644
--- a/src/IP.cc
+++ b/src/IP.cc
@@ -13,26 +13,26 @@
 #include "BroString.h"
 #include "Reporter.h"
 
-static RecordType* ip4_hdr_type = 0;
-static RecordType* ip6_hdr_type = 0;
-static RecordType* ip6_ext_hdr_type = 0;
-static RecordType* ip6_option_type = 0;
-static RecordType* ip6_hopopts_type = 0;
-static RecordType* ip6_dstopts_type = 0;
-static RecordType* ip6_routing_type = 0;
-static RecordType* ip6_fragment_type = 0;
-static RecordType* ip6_ah_type = 0;
-static RecordType* ip6_esp_type = 0;
-static RecordType* ip6_mob_type = 0;
-static RecordType* ip6_mob_msg_type = 0;
-static RecordType* ip6_mob_brr_type = 0;
-static RecordType* ip6_mob_hoti_type = 0;
-static RecordType* ip6_mob_coti_type = 0;
-static RecordType* ip6_mob_hot_type = 0;
-static RecordType* ip6_mob_cot_type = 0;
-static RecordType* ip6_mob_bu_type = 0;
-static RecordType* ip6_mob_back_type = 0;
-static RecordType* ip6_mob_be_type = 0;
+static RecordType* ip4_hdr_type = nullptr;
+static RecordType* ip6_hdr_type = nullptr;
+static RecordType* ip6_ext_hdr_type = nullptr;
+static RecordType* ip6_option_type = nullptr;
+static RecordType* ip6_hopopts_type = nullptr;
+static RecordType* ip6_dstopts_type = nullptr;
+static RecordType* ip6_routing_type = nullptr;
+static RecordType* ip6_fragment_type = nullptr;
+static RecordType* ip6_ah_type = nullptr;
+static RecordType* ip6_esp_type = nullptr;
+static RecordType* ip6_mob_type = nullptr;
+static RecordType* ip6_mob_msg_type = nullptr;
+static RecordType* ip6_mob_brr_type = nullptr;
+static RecordType* ip6_mob_hoti_type = nullptr;
+static RecordType* ip6_mob_coti_type = nullptr;
+static RecordType* ip6_mob_hot_type = nullptr;
+static RecordType* ip6_mob_cot_type = nullptr;
+static RecordType* ip6_mob_bu_type = nullptr;
+static RecordType* ip6_mob_back_type = nullptr;
+static RecordType* ip6_mob_be_type = nullptr;
 
 static inline RecordType* hdrType(RecordType*& type, const char* name)
 	{
@@ -79,7 +79,7 @@ static VectorVal* BuildOptionsVal(const u_char* data, int len)
 
 RecordVal* IPv6_Hdr::BuildRecordVal(VectorVal* chain) const
 	{
-	RecordVal* rv = 0;
+	RecordVal* rv = nullptr;
 
 	switch ( type ) {
 	case IPPROTO_IPV6:
@@ -330,7 +330,7 @@ IPAddr IP_Hdr::DstAddr() const
 
 RecordVal* IP_Hdr::BuildIPHdrVal() const
 	{
-	RecordVal* rval = 0;
+	RecordVal* rval = nullptr;
 
 	if ( ip4 )
 		{
@@ -354,7 +354,7 @@ RecordVal* IP_Hdr::BuildIPHdrVal() const
 
 RecordVal* IP_Hdr::BuildPktHdrVal() const
 	{
-	static RecordType* pkt_hdr_type = 0;
+	static RecordType* pkt_hdr_type = nullptr;
 
 	if ( ! pkt_hdr_type )
 		pkt_hdr_type = internal_type("pkt_hdr")->AsRecordType();
@@ -365,9 +365,9 @@ RecordVal* IP_Hdr::BuildPktHdrVal() const
 
 RecordVal* IP_Hdr::BuildPktHdrVal(RecordVal* pkt_hdr, int sindex) const
 	{
-	static RecordType* tcp_hdr_type = 0;
-	static RecordType* udp_hdr_type = 0;
-	static RecordType* icmp_hdr_type = 0;
+	static RecordType* tcp_hdr_type = nullptr;
+	static RecordType* udp_hdr_type = nullptr;
+	static RecordType* icmp_hdr_type = nullptr;
 
 	if ( ! tcp_hdr_type )
 		{
diff --git a/src/IP.h b/src/IP.h
index 287bcf8fad..5eaac66a2b 100644
--- a/src/IP.h
+++ b/src/IP.h
@@ -136,7 +136,7 @@ public:
 	/**
 	 * Returns the script-layer record representation of the header.
 	 */
-	RecordVal* BuildRecordVal(VectorVal* chain = 0) const;
+	RecordVal* BuildRecordVal(VectorVal* chain = nullptr) const;
 
 protected:
 	uint8_t type;
@@ -184,7 +184,7 @@ public:
 	 */
 	const struct ip6_frag* GetFragHdr() const
 		{ return IsFragment() ?
-				(const struct ip6_frag*)chain[chain.size()-1]->Data(): 0; }
+				(const struct ip6_frag*)chain[chain.size()-1]->Data(): nullptr; }
 
 	/**
 	 * If the header chain is a fragment, returns the offset in number of bytes
diff --git a/src/NFA.cc b/src/NFA.cc
index f22b4e0b21..94de8260d7 100644
--- a/src/NFA.cc
+++ b/src/NFA.cc
@@ -14,11 +14,11 @@ static int nfa_state_id = 0;
 NFA_State::NFA_State(int arg_sym, EquivClass* ec)
 	{
 	sym = arg_sym;
-	ccl = 0;
+	ccl = nullptr;
 	accept = NO_ACCEPT;
 	first_trans_is_back_ref = false;
-	mark = 0;
-	epsclosure = 0;
+	mark = nullptr;
+	epsclosure = nullptr;
 	id = ++nfa_state_id;
 
 	// Fix up equivalence classes based on this transition.  Note that any
@@ -39,9 +39,9 @@ NFA_State::NFA_State(CCL* arg_ccl)
 	ccl = arg_ccl;
 	accept = NO_ACCEPT;
 	first_trans_is_back_ref = false;
-	mark = 0;
+	mark = nullptr;
 	id = ++nfa_state_id;
-	epsclosure = 0;
+	epsclosure = nullptr;
 	}
 
 NFA_State::~NFA_State()
@@ -67,7 +67,7 @@ NFA_State* NFA_State::DeepCopy()
 		return mark;
 		}
 
-	NFA_State* copy = ccl ? new NFA_State(ccl) : new NFA_State(sym, 0);
+	NFA_State* copy = ccl ? new NFA_State(ccl) : new NFA_State(sym, nullptr);
 	SetMark(copy);
 
 	for ( int i = 0; i < xtions.length(); ++i )
@@ -80,7 +80,7 @@ void NFA_State::ClearMarks()
 	{
 	if ( mark )
 		{
-		SetMark(0);
+		SetMark(nullptr);
 		for ( int i = 0; i < xtions.length(); ++i )
 			xtions[i]->ClearMarks();
 		}
@@ -125,7 +125,7 @@ NFA_state_list* NFA_State::EpsilonClosure()
 
 	// Clear out markers.
 	for ( i = 0; i < states.length(); ++i )
-		states[i]->SetMark(0);
+		states[i]->SetMark(nullptr);
 
 	// Make it fit.
 	epsclosure->resize(0);
@@ -262,7 +262,7 @@ void NFA_Machine::MakePositiveClosure()
 
 void NFA_Machine::MakeRepl(int lower, int upper)
 	{
-	NFA_Machine* dup = 0;
+	NFA_Machine* dup = nullptr;
 	if ( upper > lower || upper == NO_UPPER_BOUND )
 		dup = DuplicateMachine();
 
diff --git a/src/NFA.h b/src/NFA.h
index 6b6827acc2..77e0102fba 100644
--- a/src/NFA.h
+++ b/src/NFA.h
@@ -78,12 +78,12 @@ protected:
 
 class EpsilonState : public NFA_State {
 public:
-	EpsilonState()	: NFA_State(SYM_EPSILON, 0)	{ }
+	EpsilonState()	: NFA_State(SYM_EPSILON, nullptr)	{ }
 };
 
 class NFA_Machine : public BroObj {
 public:
-	explicit NFA_Machine(NFA_State* first, NFA_State* final = 0);
+	explicit NFA_Machine(NFA_State* first, NFA_State* final = nullptr);
 	~NFA_Machine() override;
 
 	NFA_State* FirstState() const	{ return first_state; }
diff --git a/src/Net.cc b/src/Net.cc
index 6aa3177639..21542aad04 100644
--- a/src/Net.cc
+++ b/src/Net.cc
@@ -115,7 +115,7 @@ RETSIGTYPE watchdog(int /* signo */)
 					if ( ! pkt_dumper || pkt_dumper->IsError() )
 						{
 						reporter->Error("watchdog: can't open watchdog-pkt.pcap for writing");
-						pkt_dumper = 0;
+						pkt_dumper = nullptr;
 						}
 					}
 
diff --git a/src/Net.h b/src/Net.h
index 8dd643c399..9d556456ac 100644
--- a/src/Net.h
+++ b/src/Net.h
@@ -30,7 +30,7 @@ extern void net_delete();	// Reclaim all memory, etc.
 extern void net_update_time(double new_network_time);
 extern void net_packet_dispatch(double t, const Packet* pkt,
 			iosource::PktSrc* src_ps);
-extern void expire_timers(iosource::PktSrc* src_ps = 0);
+extern void expire_timers(iosource::PktSrc* src_ps = nullptr);
 extern void zeek_terminate_loop(const char* reason);
 
 // Functions to temporarily suspend processing of live input (network packets
diff --git a/src/Obj.cc b/src/Obj.cc
index 43cee1e7d6..89edc8edff 100644
--- a/src/Obj.cc
+++ b/src/Obj.cc
@@ -165,7 +165,7 @@ void BroObj::DoMsg(ODesc* d, const char s1[], const BroObj* obj2,
 	d->Add(s1);
 	PinPoint(d, obj2, pinpoint_only);
 
-	const Location* loc2 = 0;
+	const Location* loc2 = nullptr;
 	if ( obj2 && obj2->GetLocationInfo() != &no_location &&
 		 *obj2->GetLocationInfo() != *GetLocationInfo() )
 		loc2 = obj2->GetLocationInfo();
diff --git a/src/Obj.h b/src/Obj.h
index ec09dd8571..cab0ab92d5 100644
--- a/src/Obj.h
+++ b/src/Obj.h
@@ -66,7 +66,7 @@ public:
 		// we check for whether start_location has a line number
 		// of 0, which should only happen if it's been assigned
 		// to no_location (or hasn't been initialized at all).
-		location = 0;
+		location = nullptr;
 		if ( start_location.first_line != 0 )
 			SetLocationInfo(&start_location, &end_location);
 		}
@@ -80,14 +80,14 @@ public:
 	// Report user warnings/errors.  If obj2 is given, then it's
 	// included in the message, though if pinpoint_only is non-zero,
 	// then obj2 is only used to pinpoint the location.
-	void Warn(const char* msg, const BroObj* obj2 = 0,
-			bool pinpoint_only = false, const Location* expr_location = 0) const;
-	void Error(const char* msg, const BroObj* obj2 = 0,
-			bool pinpoint_only = false, const Location* expr_location = 0) const;
+	void Warn(const char* msg, const BroObj* obj2 = nullptr,
+			bool pinpoint_only = false, const Location* expr_location = nullptr) const;
+	void Error(const char* msg, const BroObj* obj2 = nullptr,
+			bool pinpoint_only = false, const Location* expr_location = nullptr) const;
 
 	// Report internal errors.
-	void BadTag(const char* msg, const char* t1 = 0,
-			const char* t2 = 0) const;
+	void BadTag(const char* msg, const char* t1 = nullptr,
+			const char* t2 = nullptr) const;
 #define CHECK_TAG(t1, t2, text, tag_to_text_func) \
 	{ \
 	if ( t1 != t2 ) \
@@ -134,9 +134,9 @@ protected:
 private:
 	friend class SuppressErrors;
 
-	void DoMsg(ODesc* d, const char s1[], const BroObj* obj2 = 0,
-			bool pinpoint_only = false, const Location* expr_location = 0) const;
-	void PinPoint(ODesc* d, const BroObj* obj2 = 0,
+	void DoMsg(ODesc* d, const char s1[], const BroObj* obj2 = nullptr,
+			bool pinpoint_only = false, const Location* expr_location = nullptr) const;
+	void PinPoint(ODesc* d, const BroObj* obj2 = nullptr,
 			bool pinpoint_only = false) const;
 
 	friend inline void Ref(BroObj* o);
diff --git a/src/OpaqueVal.cc b/src/OpaqueVal.cc
index b8d7669d54..607376ed60 100644
--- a/src/OpaqueVal.cc
+++ b/src/OpaqueVal.cc
@@ -699,24 +699,24 @@ bool EntropyVal::DoUnserialize(const broker::data& data)
 BloomFilterVal::BloomFilterVal()
 	: OpaqueVal(bloomfilter_type)
 	{
-	type = 0;
-	hash = 0;
-	bloom_filter = 0;
+	type = nullptr;
+	hash = nullptr;
+	bloom_filter = nullptr;
 	}
 
 BloomFilterVal::BloomFilterVal(OpaqueType* t)
 	: OpaqueVal(t)
 	{
-	type = 0;
-	hash = 0;
-	bloom_filter = 0;
+	type = nullptr;
+	hash = nullptr;
+	bloom_filter = nullptr;
 	}
 
 BloomFilterVal::BloomFilterVal(probabilistic::BloomFilter* bf)
 	: OpaqueVal(bloomfilter_type)
 	{
-	type = 0;
-	hash = 0;
+	type = nullptr;
+	hash = nullptr;
 	bloom_filter = bf;
 	}
 
@@ -790,13 +790,13 @@ IntrusivePtr<BloomFilterVal> BloomFilterVal::Merge(const BloomFilterVal* x,
 	     ! same_type(x->Type(), y->Type()) )
 		{
 		reporter->Error("cannot merge Bloom filters with different types");
-		return 0;
+		return nullptr;
 		}
 
 	if ( typeid(*x->bloom_filter) != typeid(*y->bloom_filter) )
 		{
 		reporter->Error("cannot merge different Bloom filter types");
-		return 0;
+		return nullptr;
 		}
 
 	probabilistic::BloomFilter* copy = x->bloom_filter->Clone();
@@ -805,7 +805,7 @@ IntrusivePtr<BloomFilterVal> BloomFilterVal::Merge(const BloomFilterVal* x,
 		{
 		delete copy;
 		reporter->Error("failed to merge Bloom filter");
-		return 0;
+		return nullptr;
 		}
 
 	auto merged = make_intrusive<BloomFilterVal>(copy);
@@ -813,7 +813,7 @@ IntrusivePtr<BloomFilterVal> BloomFilterVal::Merge(const BloomFilterVal* x,
 	if ( x->Type() && ! merged->Typify(x->Type()) )
 		{
 		reporter->Error("failed to set type on merged Bloom filter");
-		return 0;
+		return nullptr;
 		}
 
 	return merged;
@@ -876,17 +876,17 @@ bool BloomFilterVal::DoUnserialize(const broker::data& data)
 
 CardinalityVal::CardinalityVal() : OpaqueVal(cardinality_type)
 	{
-	c = 0;
-	type = 0;
-	hash = 0;
+	c = nullptr;
+	type = nullptr;
+	hash = nullptr;
 	}
 
 CardinalityVal::CardinalityVal(probabilistic::CardinalityCounter* arg_c)
 	: OpaqueVal(cardinality_type)
 	{
 	c = arg_c;
-	type = 0;
-	hash = 0;
+	type = nullptr;
+	hash = nullptr;
 	}
 
 CardinalityVal::~CardinalityVal()
diff --git a/src/Options.cc b/src/Options.cc
index c4f864189a..a68f76595c 100644
--- a/src/Options.cc
+++ b/src/Options.cc
@@ -186,49 +186,49 @@ zeek::Options zeek::parse_cmdline(int argc, char** argv)
 		}
 
 	constexpr struct option long_opts[] = {
-		{"parse-only",	no_argument,		0,	'a'},
-		{"bare-mode",	no_argument,		0,	'b'},
-		{"debug-script",	no_argument,		0,	'd'},
-		{"exec",		required_argument,	0,	'e'},
-		{"filter",		required_argument,	0,	'f'},
-		{"help",		no_argument,		0,	'h'},
-		{"iface",		required_argument,	0,	'i'},
-		{"zeekygen",		required_argument,		0,	'X'},
-		{"prefix",		required_argument,	0,	'p'},
-		{"readfile",		required_argument,	0,	'r'},
-		{"rulefile",		required_argument,	0,	's'},
-		{"tracefile",		required_argument,	0,	't'},
-		{"writefile",		required_argument,	0,	'w'},
-		{"version",		no_argument,		0,	'v'},
-		{"no-checksums",	no_argument,		0,	'C'},
-		{"force-dns",		no_argument,		0,	'F'},
-		{"load-seeds",		required_argument,	0,	'G'},
-		{"save-seeds",		required_argument,	0,	'H'},
-		{"print-plugins",	no_argument,		0,	'N'},
-		{"prime-dns",		no_argument,		0,	'P'},
-		{"time",		no_argument,		0,	'Q'},
-		{"debug-rules",		no_argument,		0,	'S'},
-		{"re-level",		required_argument,	0,	'T'},
-		{"watchdog",		no_argument,		0,	'W'},
-		{"print-id",		required_argument,	0,	'I'},
-		{"status-file",		required_argument,	0,	'U'},
+		{"parse-only",	no_argument,		nullptr,	'a'},
+		{"bare-mode",	no_argument,		nullptr,	'b'},
+		{"debug-script",	no_argument,		nullptr,	'd'},
+		{"exec",		required_argument,	nullptr,	'e'},
+		{"filter",		required_argument,	nullptr,	'f'},
+		{"help",		no_argument,		nullptr,	'h'},
+		{"iface",		required_argument,	nullptr,	'i'},
+		{"zeekygen",		required_argument,		nullptr,	'X'},
+		{"prefix",		required_argument,	nullptr,	'p'},
+		{"readfile",		required_argument,	nullptr,	'r'},
+		{"rulefile",		required_argument,	nullptr,	's'},
+		{"tracefile",		required_argument,	nullptr,	't'},
+		{"writefile",		required_argument,	nullptr,	'w'},
+		{"version",		no_argument,		nullptr,	'v'},
+		{"no-checksums",	no_argument,		nullptr,	'C'},
+		{"force-dns",		no_argument,		nullptr,	'F'},
+		{"load-seeds",		required_argument,	nullptr,	'G'},
+		{"save-seeds",		required_argument,	nullptr,	'H'},
+		{"print-plugins",	no_argument,		nullptr,	'N'},
+		{"prime-dns",		no_argument,		nullptr,	'P'},
+		{"time",		no_argument,		nullptr,	'Q'},
+		{"debug-rules",		no_argument,		nullptr,	'S'},
+		{"re-level",		required_argument,	nullptr,	'T'},
+		{"watchdog",		no_argument,		nullptr,	'W'},
+		{"print-id",		required_argument,	nullptr,	'I'},
+		{"status-file",		required_argument,	nullptr,	'U'},
 
 #ifdef	DEBUG
-		{"debug",		required_argument,	0,	'B'},
+		{"debug",		required_argument,	nullptr,	'B'},
 #endif
 #ifdef	USE_IDMEF
-		{"idmef-dtd",		required_argument,	0,	'n'},
+		{"idmef-dtd",		required_argument,	nullptr,	'n'},
 #endif
 #ifdef	USE_PERFTOOLS_DEBUG
-		{"mem-leaks",	no_argument,		0,	'm'},
-		{"mem-profile",	no_argument,		0,	'M'},
+		{"mem-leaks",	no_argument,		nullptr,	'm'},
+		{"mem-profile",	no_argument,		nullptr,	'M'},
 #endif
 
-		{"pseudo-realtime",	optional_argument, 0,	'E'},
-		{"jobs",	optional_argument, 0,	'j'},
-		{"test",		no_argument,		0,	'#'},
+		{"pseudo-realtime",	optional_argument, nullptr,	'E'},
+		{"jobs",	optional_argument, nullptr,	'j'},
+		{"test",		no_argument,		nullptr,	'#'},
 
-		{0,			0,			0,	0},
+		{nullptr,			0,			nullptr,	0},
 	};
 
 	char opts[256];
diff --git a/src/PolicyFile.cc b/src/PolicyFile.cc
index a6f93c8d88..470194b3a1 100644
--- a/src/PolicyFile.cc
+++ b/src/PolicyFile.cc
@@ -18,8 +18,8 @@ using namespace std;
 #include "Reporter.h"
 
 struct PolicyFile {
-	PolicyFile ()	{ filedata = 0; lmtime = 0; }
-	~PolicyFile ()	{ delete [] filedata; filedata = 0; }
+	PolicyFile ()	{ filedata = nullptr; lmtime = 0; }
+	~PolicyFile ()	{ delete [] filedata; filedata = nullptr; }
 
 	time_t lmtime;
 	char* filedata;
diff --git a/src/PrefixTable.cc b/src/PrefixTable.cc
index 391d11e673..36012af5a3 100644
--- a/src/PrefixTable.cc
+++ b/src/PrefixTable.cc
@@ -28,7 +28,7 @@ void* PrefixTable::Insert(const IPAddr& addr, int width, void* data)
 	if ( ! node )
 		{
 		reporter->InternalWarning("Cannot create node in patricia tree");
-		return 0;
+		return nullptr;
 		}
 
 	void* old = node->data;
@@ -59,7 +59,7 @@ void* PrefixTable::Insert(const Val* value, void* data)
 
 	default:
 		reporter->InternalWarning("Wrong index type for PrefixTable");
-		return 0;
+		return nullptr;
 	}
 	}
 
@@ -97,7 +97,7 @@ void* PrefixTable::Lookup(const IPAddr& addr, int width, bool exact) const
 	patricia_node_t** list = nullptr;
 
 	Deref_Prefix(prefix);
-	return node ? node->data : 0;
+	return node ? node->data : nullptr;
 	}
 
 void* PrefixTable::Lookup(const Val* value, bool exact) const
@@ -120,7 +120,7 @@ void* PrefixTable::Lookup(const Val* value, bool exact) const
 	default:
 		reporter->InternalWarning("Wrong index type %d for PrefixTable",
 		                          value->Type()->Tag());
-		return 0;
+		return nullptr;
 	}
 	}
 
@@ -131,7 +131,7 @@ void* PrefixTable::Remove(const IPAddr& addr, int width)
 	Deref_Prefix(prefix);
 
 	if ( ! node )
-		return 0;
+		return nullptr;
 
 	void* old = node->data;
 	patricia_remove(tree, node);
@@ -158,7 +158,7 @@ void* PrefixTable::Remove(const Val* value)
 
 	default:
 		reporter->InternalWarning("Wrong index type for PrefixTable");
-		return 0;
+		return nullptr;
 	}
 	}
 
@@ -167,7 +167,7 @@ PrefixTable::iterator PrefixTable::InitIterator()
 	iterator i;
 	i.Xsp = i.Xstack;
 	i.Xrn = tree->head;
-	i.Xnode = 0;
+	i.Xnode = nullptr;
 	return i;
 	}
 
@@ -177,7 +177,7 @@ void* PrefixTable::GetNext(iterator* i)
 		{
 		i->Xnode = i->Xrn;
 		if ( ! i->Xnode )
-			return 0;
+			return nullptr;
 
 		if ( i->Xrn->l )
 			{
@@ -194,7 +194,7 @@ void* PrefixTable::GetNext(iterator* i)
 			i->Xrn = *(--i->Xsp);
 
 		else
-			i->Xrn = (patricia_node_t*) 0;
+			i->Xrn = (patricia_node_t*) nullptr;
 
 		if ( i->Xnode->prefix )
 			return (void*) i->Xnode->data;
diff --git a/src/PrefixTable.h b/src/PrefixTable.h
index 21b956756a..2bd640772d 100644
--- a/src/PrefixTable.h
+++ b/src/PrefixTable.h
@@ -30,10 +30,10 @@ public:
 	// Addr in network byte order. If data is zero, acts like a set.
 	// Returns ptr to old data if already existing.
 	// For existing items without data, returns non-nil if found.
-	void* Insert(const IPAddr& addr, int width, void* data = 0);
+	void* Insert(const IPAddr& addr, int width, void* data = nullptr);
 
 	// Value may be addr or subnet.
-	void* Insert(const Val* value, void* data = 0);
+	void* Insert(const Val* value, void* data = nullptr);
 
 	// Returns nil if not found, pointer to data otherwise.
 	// For items without data, returns non-nil if found.
diff --git a/src/PriorityQueue.h b/src/PriorityQueue.h
index 05de50ee69..591c79c474 100644
--- a/src/PriorityQueue.h
+++ b/src/PriorityQueue.h
@@ -34,7 +34,7 @@ public:
 	PQ_Element* Top() const
 		{
 		if ( heap_size == 0 )
-			return 0;
+			return nullptr;
 
 		return heap[0];
 		}
diff --git a/src/RE.cc b/src/RE.cc
index 183c421e17..ac59567f4d 100644
--- a/src/RE.cc
+++ b/src/RE.cc
@@ -12,10 +12,10 @@
 #include "Reporter.h"
 #include "BroString.h"
 
-CCL* curr_ccl = 0;
+CCL* curr_ccl = nullptr;
 
 Specific_RE_Matcher* rem;
-NFA_Machine* nfa = 0;
+NFA_Machine* nfa = nullptr;
 int case_insensitive = 0;
 
 extern int RE_parse(void);
@@ -27,10 +27,10 @@ Specific_RE_Matcher::Specific_RE_Matcher(match_type arg_mt, int arg_multiline)
 	{
 	mt = arg_mt;
 	multiline = arg_multiline;
-	any_ccl = 0;
-	pattern_text = 0;
-	dfa = 0;
-	ecs = 0;
+	any_ccl = nullptr;
+	pattern_text = nullptr;
+	dfa = nullptr;
+	ecs = nullptr;
 	accepted = new AcceptingSet();
 	}
 
@@ -131,7 +131,7 @@ bool Specific_RE_Matcher::Compile(bool lazy)
 		{
 		reporter->Error("error compiling pattern /%s/", pattern_text);
 		Unref(nfa);
-		nfa = 0;
+		nfa = nullptr;
 		return false;
 		}
 
@@ -141,7 +141,7 @@ bool Specific_RE_Matcher::Compile(bool lazy)
 	dfa = new DFA_Machine(nfa, EC());
 
 	Unref(nfa);
-	nfa = 0;
+	nfa = nullptr;
 
 	ecs = EC()->EquivClasses();
 
@@ -155,7 +155,7 @@ bool Specific_RE_Matcher::CompileSet(const string_list& set, const int_list& idx
 
 	rem = this;
 
-	NFA_Machine* set_nfa = 0;
+	NFA_Machine* set_nfa = nullptr;
 
 	loop_over_list(set, i)
 		{
@@ -172,7 +172,7 @@ bool Specific_RE_Matcher::CompileSet(const string_list& set, const int_list& idx
 			else
 				Unref(nfa);
 
-			nfa = 0;
+			nfa = nullptr;
 			return false;
 			}
 
@@ -257,7 +257,7 @@ bool Specific_RE_Matcher::MatchAll(const u_char* bv, int n)
 	if ( d )
 		d = d->Xtion(ecs[SYM_EOL], dfa);
 
-	return d && d->Accept() != 0;
+	return d && d->Accept() != nullptr;
 	}
 
 
@@ -354,7 +354,7 @@ bool RE_Match_State::Match(const u_char* bv, int n,
 
 		if ( ! next_state )
 			{
-			current_state = 0;
+			current_state = nullptr;
 			break;
 			}
 
diff --git a/src/RE.h b/src/RE.h
index 702767016c..dfadcaaf28 100644
--- a/src/RE.h
+++ b/src/RE.h
@@ -140,10 +140,10 @@ class RE_Match_State {
 public:
 	explicit RE_Match_State(Specific_RE_Matcher* matcher)
 		{
-		dfa = matcher->DFA() ? matcher->DFA() : 0;
+		dfa = matcher->DFA() ? matcher->DFA() : nullptr;
 		ecs = matcher->EC()->EquivClasses();
 		current_pos = -1;
-		current_state = 0;
+		current_state = nullptr;
 		}
 
 	const AcceptingMatchSet& AcceptedMatches() const
@@ -159,7 +159,7 @@ public:
 	void Clear()
 		{
 		current_pos = -1;
-		current_state = 0;
+		current_state = nullptr;
 		accepted_matches.clear();
 		}
 
diff --git a/src/Reporter.cc b/src/Reporter.cc
index df48205d05..5ab4d923b7 100644
--- a/src/Reporter.cc
+++ b/src/Reporter.cc
@@ -30,7 +30,7 @@ int closelog();
 }
 #endif
 
-Reporter* reporter = 0;
+Reporter* reporter = nullptr;
 
 Reporter::Reporter()
 	{
@@ -88,8 +88,8 @@ void Reporter::Info(const char* fmt, ...)
 	{
 	va_list ap;
 	va_start(ap, fmt);
-	FILE* out = EmitToStderr(info_to_stderr) ? stderr : 0;
-	DoLog("", reporter_info, out, 0, 0, true, true, 0, fmt, ap);
+	FILE* out = EmitToStderr(info_to_stderr) ? stderr : nullptr;
+	DoLog("", reporter_info, out, nullptr, nullptr, true, true, nullptr, fmt, ap);
 	va_end(ap);
 	}
 
@@ -97,8 +97,8 @@ void Reporter::Warning(const char* fmt, ...)
 	{
 	va_list ap;
 	va_start(ap, fmt);
-	FILE* out = EmitToStderr(warnings_to_stderr) ? stderr : 0;
-	DoLog("warning", reporter_warning, out, 0, 0, true, true, 0, fmt, ap);
+	FILE* out = EmitToStderr(warnings_to_stderr) ? stderr : nullptr;
+	DoLog("warning", reporter_warning, out, nullptr, nullptr, true, true, nullptr, fmt, ap);
 	va_end(ap);
 	}
 
@@ -107,8 +107,8 @@ void Reporter::Error(const char* fmt, ...)
 	++errors;
 	va_list ap;
 	va_start(ap, fmt);
-	FILE* out = EmitToStderr(errors_to_stderr) ? stderr : 0;
-	DoLog("error", reporter_error, out, 0, 0, true, true, 0, fmt, ap);
+	FILE* out = EmitToStderr(errors_to_stderr) ? stderr : nullptr;
+	DoLog("error", reporter_error, out, nullptr, nullptr, true, true, nullptr, fmt, ap);
 	va_end(ap);
 	}
 
@@ -118,7 +118,7 @@ void Reporter::FatalError(const char* fmt, ...)
 	va_start(ap, fmt);
 
 	// Always log to stderr.
-	DoLog("fatal error", 0, stderr, 0, 0, true, false, 0, fmt, ap);
+	DoLog("fatal error", nullptr, stderr, nullptr, nullptr, true, false, nullptr, fmt, ap);
 
 	va_end(ap);
 
@@ -134,7 +134,7 @@ void Reporter::FatalErrorWithCore(const char* fmt, ...)
 	va_start(ap, fmt);
 
 	// Always log to stderr.
-	DoLog("fatal error", 0, stderr, 0, 0, true, false, 0, fmt, ap);
+	DoLog("fatal error", nullptr, stderr, nullptr, nullptr, true, false, nullptr, fmt, ap);
 
 	va_end(ap);
 
@@ -152,8 +152,8 @@ void Reporter::ExprRuntimeError(const Expr* expr, const char* fmt, ...)
 	PushLocation(expr->GetLocationInfo());
 	va_list ap;
 	va_start(ap, fmt);
-	FILE* out = EmitToStderr(errors_to_stderr) ? stderr : 0;
-	DoLog("expression error", reporter_error, out, 0, 0, true, true,
+	FILE* out = EmitToStderr(errors_to_stderr) ? stderr : nullptr;
+	DoLog("expression error", reporter_error, out, nullptr, nullptr, true, true,
 	      d.Description(), fmt, ap);
 	va_end(ap);
 	PopLocation();
@@ -166,8 +166,8 @@ void Reporter::RuntimeError(const Location* location, const char* fmt, ...)
 	PushLocation(location);
 	va_list ap;
 	va_start(ap, fmt);
-	FILE* out = EmitToStderr(errors_to_stderr) ? stderr : 0;
-	DoLog("runtime error", reporter_error, out, 0, 0, true, true, "", fmt, ap);
+	FILE* out = EmitToStderr(errors_to_stderr) ? stderr : nullptr;
+	DoLog("runtime error", reporter_error, out, nullptr, nullptr, true, true, "", fmt, ap);
 	va_end(ap);
 	PopLocation();
 	throw InterpreterException();
@@ -179,7 +179,7 @@ void Reporter::InternalError(const char* fmt, ...)
 	va_start(ap, fmt);
 
 	// Always log to stderr.
-	DoLog("internal error", 0, stderr, 0, 0, true, false, 0, fmt, ap);
+	DoLog("internal error", nullptr, stderr, nullptr, nullptr, true, false, nullptr, fmt, ap);
 
 	va_end(ap);
 
@@ -197,7 +197,7 @@ void Reporter::AnalyzerError(analyzer::Analyzer* a, const char* fmt,
 	va_start(ap, fmt);
 	// Always log to stderr.
 	// TODO: would be nice to also log a call stack.
-	DoLog("analyzer error", reporter_error, stderr, 0, 0, true, true, 0, fmt,
+	DoLog("analyzer error", reporter_error, stderr, nullptr, nullptr, true, true, nullptr, fmt,
 	      ap);
 	va_end(ap);
 	}
@@ -206,9 +206,9 @@ void Reporter::InternalWarning(const char* fmt, ...)
 	{
 	va_list ap;
 	va_start(ap, fmt);
-	FILE* out = EmitToStderr(warnings_to_stderr) ? stderr : 0;
+	FILE* out = EmitToStderr(warnings_to_stderr) ? stderr : nullptr;
 	// TODO: would be nice to also log a call stack.
-	DoLog("internal warning", reporter_warning, out, 0, 0, true, true, 0, fmt,
+	DoLog("internal warning", reporter_warning, out, nullptr, nullptr, true, true, nullptr, fmt,
 	      ap);
 	va_end(ap);
 	}
@@ -228,7 +228,7 @@ void Reporter::WeirdHelper(EventHandlerPtr event, val_list vl, const char* fmt_n
 	{
 	va_list ap;
 	va_start(ap, fmt_name);
-	DoLog("weird", event, 0, 0, &vl, false, false, 0, fmt_name, ap);
+	DoLog("weird", event, nullptr, nullptr, &vl, false, false, nullptr, fmt_name, ap);
 	va_end(ap);
 	}
 
@@ -382,7 +382,7 @@ void Reporter::DoLog(const char* prefix, EventHandlerPtr event, FILE* out,
 
 	int size = sizeof(tmp);
 	char* buffer  = tmp;
-	char* alloced = 0;
+	char* alloced = nullptr;
 
 	string loc_str;
 
diff --git a/src/Rule.cc b/src/Rule.cc
index ade2ca3f7c..3a7533b6f6 100644
--- a/src/Rule.cc
+++ b/src/Rule.cc
@@ -87,7 +87,7 @@ void Rule::AddRequires(const char* id, bool opposite_direction, bool negate)
 	{
 	Precond* p = new Precond;
 	p->id = copy_string(id);
-	p->rule = 0;
+	p->rule = nullptr;
 	p->opposite_dir = opposite_direction;
 	p->negate = negate;
 
diff --git a/src/Rule.h b/src/Rule.h
index 5d18ae8d84..29099dcb8e 100644
--- a/src/Rule.h
+++ b/src/Rule.h
@@ -25,7 +25,7 @@ public:
 		idx = rule_counter++;
 		location = arg_location;
 		active = true;
-		next = 0;
+		next = nullptr;
 		}
 
 	~Rule();
diff --git a/src/RuleMatcher.cc b/src/RuleMatcher.cc
index f492846a4d..0abafcb4da 100644
--- a/src/RuleMatcher.cc
+++ b/src/RuleMatcher.cc
@@ -48,10 +48,10 @@ RuleHdrTest::RuleHdrTest(Prot arg_prot, uint32_t arg_offset, uint32_t arg_size,
 	size = arg_size;
 	comp = arg_comp;
 	vals = arg_vals;
-	sibling = 0;
-	child = 0;
-	pattern_rules = 0;
-	pure_rules = 0;
+	sibling = nullptr;
+	child = nullptr;
+	pattern_rules = nullptr;
+	pure_rules = nullptr;
 	ruleset = new IntSet;
 	id = ++idcounter;
 	level = 0;
@@ -65,10 +65,10 @@ RuleHdrTest::RuleHdrTest(Prot arg_prot, Comp arg_comp, vector<IPPrefix> arg_v)
 	comp = arg_comp;
 	vals = new maskedvalue_list;
 	prefix_vals = std::move(arg_v);
-	sibling = 0;
-	child = 0;
-	pattern_rules = 0;
-	pure_rules = 0;
+	sibling = nullptr;
+	child = nullptr;
+	pattern_rules = nullptr;
+	pure_rules = nullptr;
 	ruleset = new IntSet;
 	id = ++idcounter;
 	level = 0;
@@ -103,7 +103,7 @@ RuleHdrTest::RuleHdrTest(RuleHdrTest& h)
 		for ( PatternSet* orig_set : h.psets[j] )
 			{
 			PatternSet* copied_set = new PatternSet;
-			copied_set->re = 0;
+			copied_set->re = nullptr;
 			copied_set->ids = orig_set->ids;
 			for ( const auto& pattern : orig_set->patterns )
 				copied_set->patterns.push_back(copy_string(pattern));
@@ -113,10 +113,10 @@ RuleHdrTest::RuleHdrTest(RuleHdrTest& h)
 			}
 		}
 
-	sibling = 0;
-	child = 0;
-	pattern_rules = 0;
-	pure_rules = 0;
+	sibling = nullptr;
+	child = nullptr;
+	pattern_rules = nullptr;
+	pure_rules = nullptr;
 	ruleset = new IntSet;
 	id = ++idcounter;
 	level = 0;
@@ -758,8 +758,8 @@ RuleEndpointState* RuleMatcher::InitEndpoint(analyzer::Analyzer* analyzer,
 		// Evaluate all rules on this node which don't contain
 		// any patterns.
 		for ( Rule* r = hdr_test->pure_rules; r; r = r->next )
-			if ( EvalRuleConditions(r, state, 0, 0, false) )
-				ExecRuleActions(r, state, 0, 0, false);
+			if ( EvalRuleConditions(r, state, nullptr, 0, false) )
+				ExecRuleActions(r, state, nullptr, 0, false);
 
 		// If we're on or above the RE_level, we may have some
 		// pattern matching to do.
@@ -989,7 +989,7 @@ void RuleMatcher::ExecPureRules(RuleEndpointState* state, bool eos)
 	for ( const auto& hdr_test : state->hdr_tests )
 		{
 		for ( Rule* r = hdr_test->pure_rules; r; r = r->next )
-			ExecRulePurely(r, 0, state, eos);
+			ExecRulePurely(r, nullptr, state, eos);
 		}
 	}
 
@@ -1001,14 +1001,14 @@ bool RuleMatcher::ExecRulePurely(Rule* r, BroString* s,
 
 	DBG_LOG(DBG_RULES, "Checking rule %s purely", r->ID());
 
-	if ( EvalRuleConditions(r, state, 0, 0, eos) )
+	if ( EvalRuleConditions(r, state, nullptr, 0, eos) )
 		{
 		DBG_LOG(DBG_RULES, "MATCH!");
 
 		if ( s )
 			ExecRuleActions(r, state, s->Bytes(), s->Len(), eos);
 		else
-			ExecRuleActions(r, state, 0, 0, eos);
+			ExecRuleActions(r, state, nullptr, 0, eos);
 
 		return true;
 		}
@@ -1098,7 +1098,7 @@ void RuleMatcher::ExecRule(Rule* rule, RuleEndpointState* state, bool eos)
 		for ( Rule* r = h->pure_rules; r; r = r->next )
 			if ( r == rule )
 				{ // found, so let's evaluate it
-				ExecRulePurely(rule, 0, state, eos);
+				ExecRulePurely(rule, nullptr, state, eos);
 				return;
 				}
 
@@ -1273,7 +1273,7 @@ static Val* get_bro_val(const char* label)
 	if ( ! id )
 		{
 		rules_error("unknown script-level identifier", label);
-		return 0;
+		return nullptr;
 		}
 
 	return id->ID_Val();
@@ -1464,7 +1464,7 @@ void RuleMatcherState::FinishEndpointMatcher()
 	delete orig_match_state;
 	delete resp_match_state;
 
-	orig_match_state = resp_match_state = 0;
+	orig_match_state = resp_match_state = nullptr;
 	}
 
 void RuleMatcherState::Match(Rule::PatternType type, const u_char* data,
diff --git a/src/RuleMatcher.h b/src/RuleMatcher.h
index d5f958c2a5..6e0cd864a5 100644
--- a/src/RuleMatcher.h
+++ b/src/RuleMatcher.h
@@ -67,7 +67,7 @@ typedef PList<BroString> bstr_list;
 
 // Get values from Bro's script-level variables.
 extern void id_to_maskedvallist(const char* id, maskedvalue_list* append_to,
-                                vector<IPPrefix>* prefix_vector = 0);
+                                vector<IPPrefix>* prefix_vector = nullptr);
 extern char* id_to_str(const char* id);
 extern uint32_t id_to_uint(const char* id);
 
@@ -255,7 +255,7 @@ public:
 	 * @return The results of the signature matching.
 	 */
 	MIME_Matches* Match(RuleFileMagicState* state, const u_char* data,
-	                   uint64_t len, MIME_Matches* matches = 0) const;
+	                   uint64_t len, MIME_Matches* matches = nullptr) const;
 
 
 	/**
@@ -312,7 +312,7 @@ public:
 	Val* BuildRuleStateValue(const Rule* rule,
 					const RuleEndpointState* state) const;
 
-	void GetStats(Stats* stats, RuleHdrTest* hdr_test = 0);
+	void GetStats(Stats* stats, RuleHdrTest* hdr_test = nullptr);
 	void DumpStats(BroFile* f);
 
 private:
@@ -372,13 +372,13 @@ private:
 // Keeps bi-directional matching-state.
 class RuleMatcherState {
 public:
-	RuleMatcherState()	{ orig_match_state = resp_match_state = 0; }
+	RuleMatcherState()	{ orig_match_state = resp_match_state = nullptr; }
 	~RuleMatcherState()
 		{ delete orig_match_state; delete resp_match_state; }
 
 	// ip may be nil.
 	void InitEndpointMatcher(analyzer::Analyzer* analyzer, const IP_Hdr* ip,
-				 int caplen, bool from_orig, analyzer::pia::PIA* pia = 0);
+				 int caplen, bool from_orig, analyzer::pia::PIA* pia = nullptr);
 
 	// bol/eol should be set to false for type Rule::PAYLOAD; they're
 	// deduced automatically.
diff --git a/src/Scope.cc b/src/Scope.cc
index c75dc64410..c324c6a134 100644
--- a/src/Scope.cc
+++ b/src/Scope.cc
@@ -20,7 +20,7 @@ Scope::Scope(IntrusivePtr<ID> id, attr_list* al)
 	: scope_id(std::move(id))
 	{
 	attrs = al;
-	return_type = 0;
+	return_type = nullptr;
 
 	inits = new id_list;
 
@@ -65,7 +65,7 @@ ID* Scope::GenerateTemporary(const char* name)
 id_list* Scope::GetInits()
 	{
 	id_list* ids = inits;
-	inits = 0;
+	inits = nullptr;
 	return ids;
 	}
 
@@ -76,9 +76,9 @@ void Scope::Describe(ODesc* d) const
 
 	else
 		{
-		d->Add(scope_id != 0);
+		d->Add(scope_id != nullptr);
 		d->SP();
-		d->Add(return_type != 0);
+		d->Add(return_type != nullptr);
 		d->SP();
 		d->Add(static_cast<uint64_t>(local.size()));
 		d->SP();
@@ -149,7 +149,7 @@ IntrusivePtr<ID> lookup_ID(const char* name, const char* curr_module,
 			return {NewRef{}, id};
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 IntrusivePtr<ID> install_ID(const char* name, const char* module_name,
diff --git a/src/SerializationFormat.cc b/src/SerializationFormat.cc
index 1aa8346f3f..f2dd26bf5b 100644
--- a/src/SerializationFormat.cc
+++ b/src/SerializationFormat.cc
@@ -29,7 +29,7 @@ void SerializationFormat::StartRead(const char* data, uint32_t arg_len)
 
 void SerializationFormat::EndRead()
 	{
-	input = 0;
+	input = nullptr;
 	}
 
 void SerializationFormat::StartWrite()
@@ -37,7 +37,7 @@ void SerializationFormat::StartWrite()
 	if ( output && output_size > INITIAL_SIZE )
 		{
 		free(output);
-		output = 0;
+		output = nullptr;
 		}
 
 	if ( ! output )
@@ -54,7 +54,7 @@ uint32_t SerializationFormat::EndWrite(char** data)
 	{
 	uint32_t rval = output_pos;
 	*data = output;
-	output = 0;
+	output = nullptr;
 	output_size = 0;
 	output_pos = 0;
 	return rval;
@@ -193,7 +193,7 @@ bool BinarySerializationFormat::Read(char** str, int* len, const char* tag)
 	if ( ! ReadData(s, l) )
 		{
 		delete [] s;
-		*str = 0;
+		*str = nullptr;
 		return false;
 		}
 
diff --git a/src/Sessions.cc b/src/Sessions.cc
index ba40f08cad..104a39f28e 100644
--- a/src/Sessions.cc
+++ b/src/Sessions.cc
@@ -68,16 +68,16 @@ NetSessions::NetSessions()
 	if ( stp_correlate_pair )
 		stp_manager = new analyzer::stepping_stone::SteppingStoneManager();
 	else
-		stp_manager = 0;
+		stp_manager = nullptr;
 
 	discarder = new Discarder();
 	if ( ! discarder->IsActive() )
 		{
 		delete discarder;
-		discarder = 0;
+		discarder = nullptr;
 		}
 
-	packet_filter = 0;
+	packet_filter = nullptr;
 
 	dump_this_packet = false;
 	num_packets_processed = 0;
@@ -86,12 +86,12 @@ NetSessions::NetSessions()
 		pkt_profiler = new PacketProfiler(pkt_profile_mode,
 				pkt_profile_freq, pkt_profile_file->AsFile());
 	else
-		pkt_profiler = 0;
+		pkt_profiler = nullptr;
 
 	if ( arp_request || arp_reply || bad_arp )
 		arp_analyzer = new analyzer::arp::ARP_Analyzer();
 	else
-		arp_analyzer = 0;
+		arp_analyzer = nullptr;
 
 	memset(&stats, 0, sizeof(SessionStats));
 	}
@@ -153,7 +153,7 @@ void NetSessions::NextPacket(double t, const Packet* pkt)
 
 		const struct ip* ip = (const struct ip*) (pkt->data + pkt->hdr_size);
 		IP_Hdr ip_hdr(ip, false);
-		DoNextPacket(t, pkt, &ip_hdr, 0);
+		DoNextPacket(t, pkt, &ip_hdr, nullptr);
 		}
 
 	else if ( pkt->l3_proto == L3_IPV6 )
@@ -165,7 +165,7 @@ void NetSessions::NextPacket(double t, const Packet* pkt)
 			}
 
 		IP_Hdr ip_hdr((const struct ip6_hdr*) (pkt->data + pkt->hdr_size), false, caplen);
-		DoNextPacket(t, pkt, &ip_hdr, 0);
+		DoNextPacket(t, pkt, &ip_hdr, nullptr);
 		}
 
 	else if ( pkt->l3_proto == L3_ARP )
@@ -261,7 +261,7 @@ void NetSessions::DoNextPacket(double t, const Packet* pkt, const IP_Hdr* ip_hdr
 	if ( discarder && discarder->NextPacket(ip_hdr, len, caplen) )
 		return;
 
-	FragReassembler* f = 0;
+	FragReassembler* f = nullptr;
 
 	if ( ip_hdr->IsFragment() )
 		{
@@ -574,7 +574,7 @@ void NetSessions::DoNextPacket(double t, const Packet* pkt, const IP_Hdr* ip_hdr
 			return;
 			}
 
-		IP_Hdr* inner = 0;
+		IP_Hdr* inner = nullptr;
 
 		if ( gre_version != 0 )
 			{
@@ -662,7 +662,7 @@ void NetSessions::DoNextPacket(double t, const Packet* pkt, const IP_Hdr* ip_hdr
 		// We already know that connection.
 		if ( conn->IsReuse(t, data) )
 			{
-			conn->Event(connection_reused, 0);
+			conn->Event(connection_reused, nullptr);
 
 			Remove(conn);
 			conn = NewConn(key, t, &id, data, proto, ip_hdr->FlowLabel(), pkt, encapsulation);
@@ -686,16 +686,16 @@ void NetSessions::DoNextPacket(double t, const Packet* pkt, const IP_Hdr* ip_hdr
 
 	conn->CheckFlowLabel(is_orig, ip_hdr->FlowLabel());
 
-	Val* pkt_hdr_val = 0;
+	Val* pkt_hdr_val = nullptr;
 
 	if ( ipv6_ext_headers && ip_hdr->NumHeaders() > 1 )
 		{
 		pkt_hdr_val = ip_hdr->BuildPktHdrVal();
-		conn->Event(ipv6_ext_headers, 0, pkt_hdr_val);
+		conn->Event(ipv6_ext_headers, nullptr, pkt_hdr_val);
 		}
 
 	if ( new_packet )
-		conn->Event(new_packet, 0,
+		conn->Event(new_packet, nullptr,
 		        pkt_hdr_val ? pkt_hdr_val->Ref() : ip_hdr->BuildPktHdrVal());
 
 	conn->NextPacket(t, is_orig, ip_hdr, len, caplen, data,
@@ -739,7 +739,7 @@ void NetSessions::DoNextInnerPacket(double t, const Packet* pkt,
 		    ((network_time - (double)ts.tv_sec) * 1000000);
 		}
 
-	const u_char* data = 0;
+	const u_char* data = nullptr;
 
 	if ( inner->IP4_Hdr() )
 		data = (const u_char*) inner->IP4_Hdr();
@@ -906,7 +906,7 @@ Connection* NetSessions::FindConnection(Val* v)
 	{
 	BroType* vt = v->Type();
 	if ( ! IsRecord(vt->Tag()) )
-		return 0;
+		return nullptr;
 
 	RecordType* vr = vt->AsRecordType();
 	const val_list* vl = v->AsRecord();
@@ -931,7 +931,7 @@ Connection* NetSessions::FindConnection(Val* v)
 		resp_p = vr->FieldOffset("resp_p");
 
 		if ( orig_h < 0 || resp_h < 0 || orig_p < 0 || resp_p < 0 )
-			return 0;
+			return nullptr;
 
 		// ### we ought to check that the fields have the right
 		// types, too.
@@ -967,7 +967,7 @@ Connection* NetSessions::FindConnection(Val* v)
 		// This can happen due to pseudo-connections we
 		// construct, for example for packet headers embedded
 		// in ICMPs.
-		return 0;
+		return nullptr;
 		}
 
 	Connection* conn = nullptr;
@@ -1151,7 +1151,7 @@ Connection* NetSessions::NewConn(const ConnIDKey& k, double t, const ConnID* id,
 			break;
 		default:
 			reporter->InternalWarning("unknown transport protocol");
-			return 0;
+			return nullptr;
 	};
 
 	if ( tproto == TRANSPORT_TCP )
@@ -1163,7 +1163,7 @@ Connection* NetSessions::NewConn(const ConnIDKey& k, double t, const ConnID* id,
 	bool flip = false;
 
 	if ( ! WantConnection(src_h, dst_h, tproto, flags, flip) )
-		return 0;
+		return nullptr;
 
 	Connection* conn = new Connection(this, k, t, id, flow_label, pkt, encapsulation);
 	conn->SetTransport(tproto);
@@ -1175,11 +1175,11 @@ Connection* NetSessions::NewConn(const ConnIDKey& k, double t, const ConnID* id,
 		{
 		conn->Done();
 		Unref(conn);
-		return 0;
+		return nullptr;
 		}
 
 	if ( new_connection )
-		conn->Event(new_connection, 0);
+		conn->Event(new_connection, nullptr);
 
 	return conn;
 	}
diff --git a/src/Sessions.h b/src/Sessions.h
index 33b9ee02f8..ade677f0b9 100644
--- a/src/Sessions.h
+++ b/src/Sessions.h
@@ -75,9 +75,9 @@ public:
 	void GetStats(SessionStats& s) const;
 
 	void Weird(const char* name, const Packet* pkt,
-	    const EncapsulationStack* encap = 0, const char* addl = "");
+	    const EncapsulationStack* encap = nullptr, const char* addl = "");
 	void Weird(const char* name, const IP_Hdr* ip,
-	    const EncapsulationStack* encap = 0, const char* addl = "");
+	    const EncapsulationStack* encap = nullptr, const char* addl = "");
 
 	PacketFilter* GetPacketFilter()
 		{
diff --git a/src/SmithWaterman.cc b/src/SmithWaterman.cc
index 31611d1d4a..c9896d3c19 100644
--- a/src/SmithWaterman.cc
+++ b/src/SmithWaterman.cc
@@ -61,22 +61,22 @@ VectorVal* BroSubstring::VecToPolicy(Vec* vec)
 	RecordType* sw_substring_type =
 		internal_type("sw_substring")->AsRecordType();
 	if ( ! sw_substring_type )
-		return 0;
+		return nullptr;
 
 	RecordType* sw_align_type =
 		internal_type("sw_align")->AsRecordType();
 	if ( ! sw_align_type )
-		return 0;
+		return nullptr;
 
 	VectorType* sw_align_vec_type =
 		internal_type("sw_align_vec")->AsVectorType();
 	if ( ! sw_align_vec_type )
-		return 0;
+		return nullptr;
 
 	VectorVal* result =
 		new VectorVal(internal_type("sw_substring_vec")->AsVectorType());
 	if ( ! result )
-		return 0;
+		return nullptr;
 
 	if ( vec )
 		{
@@ -235,9 +235,9 @@ public:
 		{
 		// Make sure access is in allowed range.
 		if ( row < 0 || row >= _rows )
-			return 0;
+			return nullptr;
 		if ( col < 0 || col >= _cols )
-			return 0;
+			return nullptr;
 
 		return &(_nodes[row * _cols + col]);
 		}
@@ -359,7 +359,7 @@ static void sw_collect_multiple(BroSubstring::Vec* result,
 				{
 				BroSubstring::Vec* old_al = *it;
 
-				if ( old_al == 0 )
+				if ( old_al == nullptr )
 					continue;
 
 				for ( BroSubstring::VecIt it2 = old_al->begin();
@@ -372,7 +372,7 @@ static void sw_collect_multiple(BroSubstring::Vec* result,
 							{
 							delete_each(new_al);
 							delete new_al;
-							new_al = 0;
+							new_al = nullptr;
 							goto end_loop;
 							}
 
@@ -398,7 +398,7 @@ end_loop:
 		{
 		BroSubstring::Vec* al = *it;
 
-		if ( al == 0 )
+		if ( al == nullptr )
 			continue;
 
 		for ( BroSubstring::VecIt it2 = al->begin();
@@ -432,8 +432,8 @@ BroSubstring::Vec* smith_waterman(const BroString* s1, const BroString* s2,
 	byte_vec string2 = s2->Bytes();
 
 	SWNodeMatrix matrix(s1, s2);	// dynamic programming matrix.
-	SWNode* node_max = 0;	// pointer to the best score's node
-	SWNode* node_br_max = 0;	// pointer to lowest-right matching node
+	SWNode* node_max = nullptr;	// pointer to the best score's node
+	SWNode* node_br_max = nullptr;	// pointer to lowest-right matching node
 
 	// The highest score in the matrix, globally.  We initialize to 1
 	// because we are only interested in real scores (initializing to
diff --git a/src/Stats.cc b/src/Stats.cc
index d05f82950e..1181f8dc9e 100644
--- a/src/Stats.cc
+++ b/src/Stats.cc
@@ -339,7 +339,7 @@ void ProfileLogger::SegmentProfile(const char* name, const Location* loc,
 
 SampleLogger::SampleLogger()
 	{
-	static TableType* load_sample_info = 0;
+	static TableType* load_sample_info = nullptr;
 
 	if ( ! load_sample_info )
 		load_sample_info = internal_type("load_sample_info")->AsTableType();
@@ -355,14 +355,14 @@ SampleLogger::~SampleLogger()
 void SampleLogger::FunctionSeen(const Func* func)
 	{
 	Val* idx = new StringVal(func->Name());
-	load_samples->Assign(idx, 0);
+	load_samples->Assign(idx, nullptr);
 	Unref(idx);
 	}
 
 void SampleLogger::LocationSeen(const Location* loc)
 	{
 	Val* idx = new StringVal(loc->filename);
-	load_samples->Assign(idx, 0);
+	load_samples->Assign(idx, nullptr);
 	Unref(idx);
 	}
 
@@ -438,7 +438,7 @@ void PacketProfiler::ProfilePkt(double t, unsigned int bytes)
 		getrusage(RUSAGE_SELF, &res);
 		gettimeofday(&ptimestamp, 0);
 
-		get_memory_usage(&last_mem, 0);
+		get_memory_usage(&last_mem, nullptr);
 		last_Utime = res.ru_utime.tv_sec + res.ru_utime.tv_usec / 1e6;
 		last_Stime = res.ru_stime.tv_sec + res.ru_stime.tv_usec / 1e6;
 		last_Rtime = ptimestamp.tv_sec + ptimestamp.tv_usec / 1e6;
@@ -462,7 +462,7 @@ void PacketProfiler::ProfilePkt(double t, unsigned int bytes)
 			ptimestamp.tv_sec + ptimestamp.tv_usec / 1e6;
 
 		uint64_t curr_mem;
-		get_memory_usage(&curr_mem, 0);
+		get_memory_usage(&curr_mem, nullptr);
 
 		file->Write(fmt("%.06f %.03f %" PRIu64 " %" PRIu64 " %.03f %.03f %.03f %" PRIu64 "\n",
 				t, time-last_timestamp, pkt_cnt, byte_cnt,
diff --git a/src/Stmt.cc b/src/Stmt.cc
index 0a7e0cdcae..5b2a7023ba 100644
--- a/src/Stmt.cc
+++ b/src/Stmt.cc
@@ -182,7 +182,7 @@ TraversalCode ExprListStmt::Traverse(TraversalCallback* cb) const
 	HANDLE_TC_STMT_POST(tc);
 	}
 
-static BroFile* print_stdout = 0;
+static BroFile* print_stdout = nullptr;
 
 static IntrusivePtr<EnumVal> lookup_enum_val(const char* module_name, const char* name)
 	{
@@ -629,7 +629,7 @@ SwitchStmt::SwitchStmt(IntrusivePtr<Expr> index, case_list* arg_cases)
 						NegExpr* ne = (NegExpr*)(expr);
 
 						if ( ne->Op()->IsConst() )
-							Unref(exprs.replace(j, new ConstExpr(ne->Eval(0))));
+							Unref(exprs.replace(j, new ConstExpr(ne->Eval(nullptr))));
 						}
 						break;
 
@@ -638,7 +638,7 @@ SwitchStmt::SwitchStmt(IntrusivePtr<Expr> index, case_list* arg_cases)
 						PosExpr* pe = (PosExpr*)(expr);
 
 						if ( pe->Op()->IsConst() )
-							Unref(exprs.replace(j, new ConstExpr(pe->Eval(0))));
+							Unref(exprs.replace(j, new ConstExpr(pe->Eval(nullptr))));
 						}
 						break;
 
@@ -648,7 +648,7 @@ SwitchStmt::SwitchStmt(IntrusivePtr<Expr> index, case_list* arg_cases)
 
 						if ( ne->Id()->IsConst() )
 							{
-							auto v = ne->Eval(0);
+							auto v = ne->Eval(nullptr);
 
 							if ( v )
 								Unref(exprs.replace(j, new ConstExpr(std::move(v))));
@@ -757,7 +757,7 @@ bool SwitchStmt::AddCaseLabelTypeMapping(ID* t, int idx)
 std::pair<int, ID*> SwitchStmt::FindCaseLabelMatch(const Val* v) const
 	{
 	int label_idx = -1;
-	ID* label_id = 0;
+	ID* label_id = nullptr;
 
 	// Find matching expression cases.
 	if ( case_label_value_map.Length() )
@@ -1065,7 +1065,7 @@ ForStmt::ForStmt(id_list* arg_loop_vars, IntrusivePtr<Expr> loop_expr)
 	: ExprStmt(STMT_FOR, std::move(loop_expr))
 	{
 	loop_vars = arg_loop_vars;
-	body = 0;
+	body = nullptr;
 
 	if ( e->Type()->Tag() == TYPE_TABLE )
 		{
@@ -1090,7 +1090,7 @@ ForStmt::ForStmt(id_list* arg_loop_vars, IntrusivePtr<Expr> loop_expr)
 				{
 				add_local({NewRef{}, (*loop_vars)[i]},
 						{NewRef{}, ind_type}, INIT_NONE,
-						0, 0, VAR_REGULAR);
+						nullptr, nullptr, VAR_REGULAR);
 				}
 			}
 		}
@@ -1106,7 +1106,7 @@ ForStmt::ForStmt(id_list* arg_loop_vars, IntrusivePtr<Expr> loop_expr)
 		BroType* t = (*loop_vars)[0]->Type();
 		if ( ! t )
 			add_local({NewRef{}, (*loop_vars)[0]}, base_type(TYPE_COUNT),
-						INIT_NONE, 0, 0, VAR_REGULAR);
+						INIT_NONE, nullptr, nullptr, VAR_REGULAR);
 
 		else if ( ! IsIntegral(t->Tag()) )
 			{
@@ -1127,7 +1127,7 @@ ForStmt::ForStmt(id_list* arg_loop_vars, IntrusivePtr<Expr> loop_expr)
 		if ( ! t )
 			add_local({NewRef{}, (*loop_vars)[0]},
 					base_type(TYPE_STRING),
-					INIT_NONE, 0, 0, VAR_REGULAR);
+					INIT_NONE, nullptr, nullptr, VAR_REGULAR);
 
 		else if ( t->Tag() != TYPE_STRING )
 			{
@@ -1158,7 +1158,7 @@ ForStmt::ForStmt(id_list* arg_loop_vars,
 		else
 			{
 			add_local(value_var, {NewRef{}, yield_type}, INIT_NONE,
-			                 0, 0, VAR_REGULAR);
+			                 nullptr, nullptr, VAR_REGULAR);
 			}
 		}
 	else
@@ -1471,7 +1471,7 @@ void ReturnStmt::Describe(ODesc* d) const
 	{
 	Stmt::Describe(d);
 	if ( ! d->IsReadable() )
-		d->Add(e != 0);
+		d->Add(e != nullptr);
 
 	if ( e )
 		{
@@ -1600,7 +1600,7 @@ IntrusivePtr<Val> EventBodyList::Exec(Frame* f, stmt_flow_type& flow) const
 
 	// Simulate a return so the hooks operate properly.
 	stmt_flow_type ft = FLOW_RETURN;
-	(void) post_execute_stmt(f->GetNextStmt(), f, 0, &ft);
+	(void) post_execute_stmt(f->GetNextStmt(), f, nullptr, &ft);
 
 	return nullptr;
 	}
@@ -1656,7 +1656,7 @@ IntrusivePtr<Val> InitStmt::Exec(Frame* f, stmt_flow_type& flow) const
 		{
 		BroType* t = aggr->Type();
 
-		Val* v = 0;
+		Val* v = nullptr;
 
 		switch ( t->Tag() ) {
 		case TYPE_RECORD:
diff --git a/src/Tag.cc b/src/Tag.cc
index f09b06c054..e0145afd6d 100644
--- a/src/Tag.cc
+++ b/src/Tag.cc
@@ -41,13 +41,13 @@ Tag::Tag()
 	{
 	type = 0;
 	subtype = 0;
-	val = 0;
+	val = nullptr;
 	}
 
 Tag::~Tag()
 	{
 	Unref(val);
-	val = 0;
+	val = nullptr;
 	}
 
 Tag& Tag::operator=(const Tag& other)
diff --git a/src/Traverse.h b/src/Traverse.h
index 2ef672ddd7..2e528905e0 100644
--- a/src/Traverse.h
+++ b/src/Traverse.h
@@ -12,7 +12,7 @@ class ID;
 
 class TraversalCallback {
 public:
-	TraversalCallback()	{ current_scope = 0; }
+	TraversalCallback()	{ current_scope = nullptr; }
 	virtual ~TraversalCallback() {}
 
 	virtual TraversalCode PreFunction(const Func*) { return TC_CONTINUE; }
diff --git a/src/Trigger.cc b/src/Trigger.cc
index 20cce502c5..f024cfbbe5 100644
--- a/src/Trigger.cc
+++ b/src/Trigger.cc
@@ -130,10 +130,10 @@ Trigger::Trigger(Expr* arg_cond, Stmt* arg_body, Stmt* arg_timeout_stmts,
 	timeout_stmts = arg_timeout_stmts;
 	timeout = arg_timeout;
 	frame = arg_frame->Clone();
-	timer = 0;
+	timer = nullptr;
 	delayed = false;
 	disabled = false;
-	attached = 0;
+	attached = nullptr;
 	is_return = arg_is_return;
 	location = arg_location;
 	timeout_value = -1;
diff --git a/src/TunnelEncapsulation.h b/src/TunnelEncapsulation.h
index 4f18b6118b..9dbf169326 100644
--- a/src/TunnelEncapsulation.h
+++ b/src/TunnelEncapsulation.h
@@ -129,7 +129,7 @@ protected:
  */
 class EncapsulationStack {
 public:
-	EncapsulationStack() : conns(0)
+	EncapsulationStack() : conns(nullptr)
 		{}
 
 	EncapsulationStack(const EncapsulationStack& other)
@@ -137,7 +137,7 @@ public:
 		if ( other.conns )
 			conns = new vector<EncapsulatingConn>(*(other.conns));
 		else
-			conns = 0;
+			conns = nullptr;
 		}
 
 	EncapsulationStack& operator=(const EncapsulationStack& other)
@@ -150,7 +150,7 @@ public:
 		if ( other.conns )
 			conns = new vector<EncapsulatingConn>(*(other.conns));
 		else
-			conns = 0;
+			conns = nullptr;
 
 		return *this;
 		}
diff --git a/src/Type.cc b/src/Type.cc
index baa1b6552a..a55781c648 100644
--- a/src/Type.cc
+++ b/src/Type.cc
@@ -541,7 +541,7 @@ void FuncType::Describe(ODesc* d) const
 		{
 		d->Add(int(Tag()));
 		d->Add(flavor);
-		d->Add(yield != 0);
+		d->Add(yield != nullptr);
 		args->DescribeFields(d);
 		if ( yield )
 			yield->Describe(d);
@@ -648,7 +648,7 @@ bool RecordType::HasField(const char* field) const
 BroType* RecordType::FieldType(const char* field) const
 	{
 	int offset = FieldOffset(field);
-	return offset >= 0 ? FieldType(offset) : 0;
+	return offset >= 0 ? FieldType(offset) : nullptr;
 	}
 
 BroType* RecordType::FieldType(int field) const
@@ -783,7 +783,7 @@ IntrusivePtr<TableVal> RecordType::GetRecordFieldsVal(const RecordVal* rv) const
 		if ( fv )
 			::Ref(fv);
 
-		bool logged = (fd->attrs && fd->FindAttr(ATTR_LOG) != 0);
+		bool logged = (fd->attrs && fd->FindAttr(ATTR_LOG) != nullptr);
 
 		auto nr = make_intrusive<RecordVal>(internal_type("record_field")->AsRecordType());
 
@@ -1575,10 +1575,10 @@ bool same_type(const BroType* t1, const BroType* t2, bool is_init, bool match_re
 bool same_attrs(const Attributes* a1, const Attributes* a2)
 	{
 	if ( ! a1 )
-		return (a2 == 0);
+		return (a2 == nullptr);
 
 	if ( ! a2 )
-		return (a1 == 0);
+		return (a1 == nullptr);
 
 	return (*a1 == *a2);
 	}
@@ -2023,7 +2023,7 @@ IntrusivePtr<BroType> init_type(Expr* init)
 	// Could be a record, a set, or a list of table elements.
 	Expr* e0 = el[0];
 
-	if ( e0->IsRecordElement(0) )
+	if ( e0->IsRecordElement(nullptr) )
 		// ListExpr's know how to build a record from their
 		// components.
 		return init_list->InitType();
@@ -2039,7 +2039,7 @@ IntrusivePtr<BroType> init_type(Expr* init)
 	for ( int i = 1; t && i < el.length(); ++i )
 		{
 		auto el_t = el[i]->InitType();
-		BroType* ti = el_t ? reduce_type(el_t.get()) : 0;
+		BroType* ti = el_t ? reduce_type(el_t.get()) : nullptr;
 
 		if ( ! ti )
 			return nullptr;
diff --git a/src/Type.h b/src/Type.h
index 82ebf7b5cf..9b4e8d111d 100644
--- a/src/Type.h
+++ b/src/Type.h
@@ -304,12 +304,12 @@ public:
 
 	bool IsSet() const
 		{
-		return tag == TYPE_TABLE && (YieldType() == 0);
+		return tag == TYPE_TABLE && (YieldType() == nullptr);
 		}
 
 	bool IsTable() const
 		{
-		return tag == TYPE_TABLE && (YieldType() != 0);
+		return tag == TYPE_TABLE && (YieldType() != nullptr);
 		}
 
 	BroType* Ref()		{ ::Ref(this); return this; }
@@ -357,7 +357,7 @@ public:
 	const type_list* Types() const	{ return &types; }
 	type_list* Types()		{ return &types; }
 
-	bool IsPure() const		{ return pure_type != 0; }
+	bool IsPure() const		{ return pure_type != nullptr; }
 
 	// Returns the underlying pure type, or nil if the list
 	// is not pure or is empty.
@@ -485,12 +485,12 @@ protected:
 
 class TypeDecl final {
 public:
-	TypeDecl(IntrusivePtr<BroType> t, const char* i, attr_list* attrs = 0, bool in_record = false);
+	TypeDecl(IntrusivePtr<BroType> t, const char* i, attr_list* attrs = nullptr, bool in_record = false);
 	TypeDecl(const TypeDecl& other);
 	~TypeDecl();
 
 	const Attr* FindAttr(attr_tag a) const
-		{ return attrs ? attrs->FindAttr(a) : 0; }
+		{ return attrs ? attrs->FindAttr(a) : nullptr; }
 
 	void DescribeReST(ODesc* d, bool roles_only = false) const;
 
@@ -547,19 +547,19 @@ public:
 	bool IsFieldDeprecated(int field) const
 		{
 		const TypeDecl* decl = FieldDecl(field);
-		return decl && decl->FindAttr(ATTR_DEPRECATED) != 0;
+		return decl && decl->FindAttr(ATTR_DEPRECATED) != nullptr;
 		}
 
 	bool FieldHasAttr(int field, attr_tag at) const
 		{
 		const TypeDecl* decl = FieldDecl(field);
-		return decl && decl->FindAttr(at) != 0;
+		return decl && decl->FindAttr(at) != nullptr;
 		}
 
 	std::string GetFieldDeprecationWarning(int field, bool has_check) const;
 
 protected:
-	RecordType() { types = 0; }
+	RecordType() { types = nullptr; }
 
 	int num_fields;
 	type_decl_list* types;
diff --git a/src/UID.h b/src/UID.h
index 711541e283..68a87758e8 100644
--- a/src/UID.h
+++ b/src/UID.h
@@ -28,7 +28,7 @@ public:
 	 * Construct a UID of a given bit-length, optionally from given values.
 	 * @see UID::Set
 	 */
-	explicit UID(bro_uint_t bits, const uint64_t* v = 0, size_t n = 0)
+	explicit UID(bro_uint_t bits, const uint64_t* v = nullptr, size_t n = 0)
 		{ Set(bits, v, n); }
 
 	/**
@@ -47,7 +47,7 @@ public:
 	 *          64, then a value is truncated to bit in desired bit-length.
 	 * @param n number of 64-bit elements in array pointed to by \a v.
 	 */
-	void Set(bro_uint_t bits, const uint64_t* v = 0, size_t n = 0);
+	void Set(bro_uint_t bits, const uint64_t* v = nullptr, size_t n = 0);
 
 	/**
 	 * Returns a base62 (characters 0-9, A-Z, a-z) representation of the UID.
diff --git a/src/Val.cc b/src/Val.cc
index 0597323b89..580ff4d58c 100644
--- a/src/Val.cc
+++ b/src/Val.cc
@@ -48,7 +48,7 @@ Val::Val(Func* f)
 
 static FileType* GetStringFileType() noexcept
 	{
-	static FileType* string_file_type = 0;
+	static FileType* string_file_type = nullptr;
 	if ( ! string_file_type )
 		string_file_type = new FileType(base_type(TYPE_STRING));
 	return string_file_type;
@@ -366,13 +366,13 @@ void Val::ValDescribeReST(ODesc* d) const
 #ifdef DEBUG
 ID* Val::GetID() const
 	{
-	return bound_id ? global_scope()->Lookup(bound_id) : 0;
+	return bound_id ? global_scope()->Lookup(bound_id) : nullptr;
 	}
 
 void Val::SetID(ID* id)
 	{
 	delete [] bound_id;
-	bound_id = id ? copy_string(id->Name()) : 0;
+	bound_id = id ? copy_string(id->Name()) : nullptr;
 	}
 #endif
 
@@ -1233,7 +1233,7 @@ TableVal* ListVal::ConvertToSet() const
 	TableVal* t = new TableVal(std::move(s));
 
 	for ( const auto& val : vals )
-		t->Assign(val, 0);
+		t->Assign(val, nullptr);
 
 	return t;
 	}
@@ -1381,16 +1381,16 @@ TableVal::TableVal(IntrusivePtr<TableType> t, IntrusivePtr<Attributes> a) : Val(
 void TableVal::Init(IntrusivePtr<TableType> t)
 	{
 	table_type = std::move(t);
-	expire_func = 0;
-	expire_time = 0;
-	expire_cookie = 0;
-	timer = 0;
-	def_val = 0;
+	expire_func = nullptr;
+	expire_time = nullptr;
+	expire_cookie = nullptr;
+	timer = nullptr;
+	def_val = nullptr;
 
 	if ( table_type->IsSubNetIndex() )
 		subnets = new PrefixTable;
 	else
-		subnets = 0;
+		subnets = nullptr;
 
 	table_hash = new CompositeHash(IntrusivePtr<TypeList>(NewRef{},
 	                               table_type->Indices()));
@@ -1603,12 +1603,12 @@ bool TableVal::AddTo(Val* val, bool is_first_init, bool propagate_ops) const
 
 		if ( type->IsSet() )
 			{
-			if ( ! t->Assign(v->Value(), k, 0) )
+			if ( ! t->Assign(v->Value(), k, nullptr) )
 				 return false;
 			}
 		else
 			{
-			if ( ! t->Assign(0, k, {NewRef{}, v->Value()}) )
+			if ( ! t->Assign(nullptr, k, {NewRef{}, v->Value()}) )
 				 return false;
 			}
 		}
@@ -1804,11 +1804,11 @@ IntrusivePtr<Val> TableVal::Default(Val* index)
 			auto coerce = make_intrusive<RecordCoerceExpr>(
 			        IntrusivePtr{NewRef{}, def_attr->AttrExpr()},
 			        IntrusivePtr{NewRef{}, ytype->AsRecordType()});
-			def_val = coerce->Eval(0);
+			def_val = coerce->Eval(nullptr);
 			}
 
 		else
-			def_val = def_attr->AttrExpr()->Eval(0);
+			def_val = def_attr->AttrExpr()->Eval(nullptr);
 		}
 
 	if ( ! def_val )
@@ -1942,7 +1942,7 @@ IntrusivePtr<TableVal> TableVal::LookupSubnetValues(const SubNetVal* search)
 		if ( entry && entry->Value() )
 			nt->Assign(s, {NewRef{}, entry->Value()});
 		else
-			nt->Assign(s, 0); // set
+			nt->Assign(s, nullptr); // set
 
 		if ( entry )
 			{
@@ -2050,7 +2050,7 @@ void TableVal::CallChangeFunc(const Val* index, Val* old_value, OnChangeType tpe
 IntrusivePtr<Val> TableVal::Delete(const Val* index)
 	{
 	HashKey* k = ComputeHash(index);
-	TableEntryVal* v = k ? AsNonConstTable()->RemoveEntry(k) : 0;
+	TableEntryVal* v = k ? AsNonConstTable()->RemoveEntry(k) : nullptr;
 	IntrusivePtr<Val> va{NewRef{}, v ? (v->Value() ? v->Value() : this) : nullptr};
 
 	if ( subnets && ! subnets->Remove(index) )
@@ -2128,7 +2128,7 @@ ListVal* TableVal::ConvertToPureList() const
 	if ( tl->length() != 1 )
 		{
 		InternalWarning("bad index type in TableVal::ConvertToPureList");
-		return 0;
+		return nullptr;
 		}
 
 	return ConvertToList((*tl)[0]->Tag());
@@ -2136,7 +2136,7 @@ ListVal* TableVal::ConvertToPureList() const
 
 Attr* TableVal::FindAttr(attr_tag t) const
 	{
-	return attrs ? attrs->FindAttr(t) : 0;
+	return attrs ? attrs->FindAttr(t) : nullptr;
 	}
 
 void TableVal::Describe(ODesc* d) const
@@ -2253,7 +2253,7 @@ bool TableVal::ExpandCompoundAndInit(val_list* vl, int k, IntrusivePtr<Val> new_
 
 bool TableVal::CheckAndAssign(Val* index, IntrusivePtr<Val> new_val)
 	{
-	Val* v = 0;
+	Val* v = nullptr;
 	if ( subnets )
 		// We need an exact match here.
 		v = (Val*) subnets->Lookup(index, true);
@@ -2392,7 +2392,7 @@ void TableVal::DoExpire(double t)
 
 	if ( ! v )
 		{
-		expire_cookie = 0;
+		expire_cookie = nullptr;
 		InitTimer(table_expire_interval);
 		}
 	else
@@ -2419,7 +2419,7 @@ double TableVal::GetExpireTime()
 	if ( interval >= 0 )
 		return interval;
 
-	expire_time = 0;
+	expire_time = nullptr;
 
 	if ( timer )
 		timer_mgr->Cancel(timer);
@@ -2819,7 +2819,7 @@ IntrusivePtr<RecordVal> RecordVal::CoerceTo(RecordType* t, bool allow_orphaning)
 	if ( same_type(Type(), t) )
 		return {NewRef{}, this};
 
-	return CoerceTo(t, 0, allow_orphaning);
+	return CoerceTo(t, nullptr, allow_orphaning);
 	}
 
 IntrusivePtr<TableVal> RecordVal::GetRecordFieldsVal() const
@@ -2975,7 +2975,7 @@ bool VectorVal::Assign(unsigned int index, IntrusivePtr<Val> element)
 	     ! same_type(element->Type(), vector_type->YieldType(), false) )
 		return false;
 
-	Val* val_at_index = 0;
+	Val* val_at_index = nullptr;
 
 	if ( index < val.vector_val->size() )
 		val_at_index = (*val.vector_val)[index];
diff --git a/src/Val.h b/src/Val.h
index 4d3e90b30e..20339e27b1 100644
--- a/src/Val.h
+++ b/src/Val.h
@@ -310,7 +310,7 @@ public:
 
 	// To be overridden by mutable derived class to enable change
 	// notification.
-	virtual notifier::Modifiable* Modifiable()	{ return 0; }
+	virtual notifier::Modifiable* Modifiable()	{ return nullptr; }
 
 #ifdef DEBUG
 	// For debugging, we keep a reference to the global ID to which a
@@ -804,7 +804,7 @@ public:
 	void ClearTimer(Timer* t)
 		{
 		if ( timer == t )
-			timer = 0;
+			timer = nullptr;
 		}
 
 	HashKey* ComputeHash(const Val* index) const;
@@ -843,7 +843,7 @@ protected:
 	IntrusivePtr<Val> Default(Val* index);
 
 	// Returns true if item expiration is enabled.
-	bool ExpirationEnabled()	{ return expire_time != 0; }
+	bool ExpirationEnabled()	{ return expire_time != nullptr; }
 
 	// Returns the expiration time defined by %{create,read,write}_expire
 	// attribute, or -1 for unset/invalid values. In the invalid case, an
diff --git a/src/Var.cc b/src/Var.cc
index 406e8ab54b..ac1a0647fb 100644
--- a/src/Var.cc
+++ b/src/Var.cc
@@ -216,7 +216,7 @@ static void make_var(ID* id, IntrusivePtr<BroType> t, init_class c,
 		// For events, add a function value (without any body) here so that
 		// we can later access the ID even if no implementations have been
 		// defined.
-		Func* f = new BroFunc(id, 0, 0, 0, 0);
+		Func* f = new BroFunc(id, nullptr, nullptr, 0, 0);
 		id->SetVal(make_intrusive<Val>(f));
 		}
 	}
@@ -305,7 +305,7 @@ static void transfer_arg_defaults(RecordType* args, RecordType* recv)
 		TypeDecl* args_i = args->FieldDecl(i);
 		TypeDecl* recv_i = recv->FieldDecl(i);
 
-		Attr* def = args_i->attrs ? args_i->attrs->FindAttr(ATTR_DEFAULT) : 0;
+		Attr* def = args_i->attrs ? args_i->attrs->FindAttr(ATTR_DEFAULT) : nullptr;
 
 		if ( ! def )
 			continue;
@@ -379,7 +379,7 @@ void begin_func(ID* id, const char* module_name, function_flavor flavor,
 		case FUNC_FLAVOR_HOOK:
 			if ( is_redef )
 				// Clear out value so it will be replaced.
-				id->SetVal(0);
+				id->SetVal(nullptr);
 			break;
 
 		case FUNC_FLAVOR_FUNCTION:
diff --git a/src/analyzer/Analyzer.cc b/src/analyzer/Analyzer.cc
index 57c74a4a2a..bb1292bab4 100644
--- a/src/analyzer/Analyzer.cc
+++ b/src/analyzer/Analyzer.cc
@@ -124,11 +124,11 @@ void Analyzer::CtorInit(const Tag& arg_tag, Connection* arg_conn)
 	skip = false;
 	finished = false;
 	removing = false;
-	parent = 0;
-	orig_supporters = 0;
-	resp_supporters = 0;
-	signature = 0;
-	output_handler = 0;
+	parent = nullptr;
+	orig_supporters = nullptr;
+	resp_supporters = nullptr;
+	signature = nullptr;
+	output_handler = nullptr;
 	}
 
 Analyzer::~Analyzer()
@@ -138,7 +138,7 @@ Analyzer::~Analyzer()
 	LOOP_OVER_CHILDREN(i)
 		delete *i;
 
-	SupportAnalyzer* next = 0;
+	SupportAnalyzer* next = nullptr;
 
 	for ( SupportAnalyzer* a = orig_supporters; a; a = next )
 		{
@@ -501,7 +501,7 @@ Analyzer* Analyzer::FindChild(ID arg_id)
 			return child;
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 Analyzer* Analyzer::FindChild(Tag arg_tag)
@@ -523,13 +523,13 @@ Analyzer* Analyzer::FindChild(Tag arg_tag)
 			return child;
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 Analyzer* Analyzer::FindChild(const char* name)
 	{
 	Tag tag = analyzer_mgr->GetComponentTag(name);
-	return tag ? FindChild(tag) : 0;
+	return tag ? FindChild(tag) : nullptr;
 	}
 
 void Analyzer::DeleteChild(analyzer_list::iterator i)
@@ -570,7 +570,7 @@ void Analyzer::AddSupportAnalyzer(SupportAnalyzer* analyzer)
 		analyzer->IsOrig() ? &orig_supporters : &resp_supporters;
 
 	// Find end of the list.
-	SupportAnalyzer* prev = 0;
+	SupportAnalyzer* prev = nullptr;
 	SupportAnalyzer* s;
 	for ( s = *head; s; prev = s, s = s->sibling )
 		;
@@ -621,7 +621,7 @@ SupportAnalyzer* Analyzer::FirstSupportAnalyzer(bool orig)
 	SupportAnalyzer* sa = orig ? orig_supporters : resp_supporters;
 
 	if ( ! sa )
-		return 0;
+		return nullptr;
 
 	if ( ! sa->Removing() )
 		return sa;
@@ -922,7 +922,7 @@ void TransportLayerAnalyzer::SetContentsFile(unsigned int /* direction */,
 BroFile* TransportLayerAnalyzer::GetContentsFile(unsigned int /* direction */) const
 	{
 	reporter->Error("analyzer type does not support writing to a contents file");
-	return 0;
+	return nullptr;
 	}
 
 void TransportLayerAnalyzer::PacketContents(const u_char* data, int len)
diff --git a/src/analyzer/Analyzer.h b/src/analyzer/Analyzer.h
index 4d25fccb27..a4bd7b7a20 100644
--- a/src/analyzer/Analyzer.h
+++ b/src/analyzer/Analyzer.h
@@ -152,7 +152,7 @@ public:
 	 * @param caplen The packet's capture length, if available.
 	 */
 	void NextPacket(int len, const u_char* data, bool is_orig,
-			uint64_t seq = -1, const IP_Hdr* ip = 0, int caplen = 0);
+			uint64_t seq = -1, const IP_Hdr* ip = nullptr, int caplen = 0);
 
 	/**
 	 * Passes stream input to the analyzer for processing. The analyzer
@@ -528,7 +528,7 @@ public:
 	 * @param len If \a data is given, the length of it.
 	 */
 	virtual void ProtocolViolation(const char* reason,
-					const char* data = 0, int len = 0);
+					const char* data = nullptr, int len = 0);
 
 	/**
 	 * Returns true if ProtocolConfirmation() has been called at least
@@ -558,13 +558,13 @@ public:
 	 * Convenience function that forwards directly to the corresponding
 	 * Connection::Event().
 	 */
-	void Event(EventHandlerPtr f, const char* name = 0);
+	void Event(EventHandlerPtr f, const char* name = nullptr);
 
 	/**
 	 * Convenience function that forwards directly to the corresponding
 	 * Connection::Event().
 	 */
-	void Event(EventHandlerPtr f, Val* v1, Val* v2 = 0);
+	void Event(EventHandlerPtr f, Val* v1, Val* v2 = nullptr);
 
 	/**
 	 * Convenience function that forwards directly to
@@ -796,7 +796,7 @@ public:
 	 * connection originator side, and otherwise for the responder side.
 	 */
 	SupportAnalyzer(const char* name, Connection* conn, bool arg_orig)
-		: Analyzer(name, conn)	{ orig = arg_orig; sibling = 0; }
+		: Analyzer(name, conn)	{ orig = arg_orig; sibling = nullptr; }
 
 	/**
 	 * Destructor.
@@ -879,7 +879,7 @@ public:
 	 * @param conn The connection the analyzer is associated with.
 	 */
 	TransportLayerAnalyzer(const char* name, Connection* conn)
-		: Analyzer(name, conn)	{ pia = 0; }
+		: Analyzer(name, conn)	{ pia = nullptr; }
 
 	/**
 	 * Overridden from parent class.
diff --git a/src/analyzer/Manager.cc b/src/analyzer/Manager.cc
index 667f371407..948e2d09b2 100644
--- a/src/analyzer/Manager.cc
+++ b/src/analyzer/Manager.cc
@@ -292,17 +292,17 @@ Analyzer* Manager::InstantiateAnalyzer(const Tag& tag, Connection* conn)
 	if ( ! c )
 		{
 		reporter->InternalWarning("request to instantiate unknown analyzer");
-		return 0;
+		return nullptr;
 		}
 
 	if ( ! c->Enabled() )
-		return 0;
+		return nullptr;
 
 	if ( ! c->Factory() )
 		{
 		reporter->InternalWarning("analyzer %s cannot be instantiated dynamically",
 					  GetComponentName(tag).c_str());
-		return 0;
+		return nullptr;
 		}
 
 	Analyzer* a = c->Factory()(conn);
@@ -310,7 +310,7 @@ Analyzer* Manager::InstantiateAnalyzer(const Tag& tag, Connection* conn)
 	if ( ! a )
 		{
 		reporter->InternalWarning("analyzer instantiation failed");
-		return 0;
+		return nullptr;
 		}
 
 	a->SetAnalyzerTag(tag);
@@ -321,12 +321,12 @@ Analyzer* Manager::InstantiateAnalyzer(const Tag& tag, Connection* conn)
 Analyzer* Manager::InstantiateAnalyzer(const char* name, Connection* conn)
 	{
 	Tag tag = GetComponentTag(name);
-	return tag ? InstantiateAnalyzer(tag, conn) : 0;
+	return tag ? InstantiateAnalyzer(tag, conn) : nullptr;
 	}
 
 Manager::tag_set* Manager::LookupPort(TransportProto proto, uint32_t port, bool add_if_not_found)
 	{
-	analyzer_map_by_port* m = 0;
+	analyzer_map_by_port* m = nullptr;
 
 	switch ( proto ) {
 	case TRANSPORT_TCP:
@@ -339,7 +339,7 @@ Manager::tag_set* Manager::LookupPort(TransportProto proto, uint32_t port, bool
 
 	default:
 		reporter->InternalWarning("unsupported transport protocol in analyzer::Manager::LookupPort");
-		return 0;
+		return nullptr;
 	}
 
 	analyzer_map_by_port::const_iterator i = m->find(port);
@@ -348,7 +348,7 @@ Manager::tag_set* Manager::LookupPort(TransportProto proto, uint32_t port, bool
 		return i->second;
 
 	if ( ! add_if_not_found )
-		return 0;
+		return nullptr;
 
 	tag_set* l = new tag_set;
 	m->insert(std::make_pair(port, l));
@@ -362,11 +362,11 @@ Manager::tag_set* Manager::LookupPort(PortVal* val, bool add_if_not_found)
 
 bool Manager::BuildInitialAnalyzerTree(Connection* conn)
 	{
-	tcp::TCP_Analyzer* tcp = 0;
-	udp::UDP_Analyzer* udp = 0;
-	icmp::ICMP_Analyzer* icmp = 0;
-	TransportLayerAnalyzer* root = 0;
-	pia::PIA* pia = 0;
+	tcp::TCP_Analyzer* tcp = nullptr;
+	udp::UDP_Analyzer* udp = nullptr;
+	icmp::ICMP_Analyzer* icmp = nullptr;
+	TransportLayerAnalyzer* root = nullptr;
+	pia::PIA* pia = nullptr;
 	bool check_port = false;
 
 	switch ( conn->ConnTransport() ) {
@@ -628,7 +628,7 @@ bool Manager::ApplyScheduledAnalyzers(Connection* conn, bool init, TransportLaye
 
 		EnumVal* tag = it->AsEnumVal();
 		Ref(tag);
-		conn->Event(scheduled_analyzer_applied, 0, tag);
+		conn->Event(scheduled_analyzer_applied, nullptr, tag);
 
 		DBG_ANALYZER_ARGS(conn, "activated %s analyzer as scheduled",
 		                  analyzer_mgr->GetComponentName(*it).c_str());
diff --git a/src/analyzer/Manager.h b/src/analyzer/Manager.h
index fe32e43be9..084f4535fb 100644
--- a/src/analyzer/Manager.h
+++ b/src/analyzer/Manager.h
@@ -311,7 +311,7 @@ public:
 	 *
 	 * @return True if at least one scheduled analyzer was found.
 	 */
-	bool ApplyScheduledAnalyzers(Connection* conn, bool init_and_event = true, TransportLayerAnalyzer* parent = 0);
+	bool ApplyScheduledAnalyzers(Connection* conn, bool init_and_event = true, TransportLayerAnalyzer* parent = nullptr);
 
 	/**
 	 * Schedules a particular analyzer for an upcoming connection. Once
diff --git a/src/analyzer/protocol/bittorrent/BitTorrentTracker.cc b/src/analyzer/protocol/bittorrent/BitTorrentTracker.cc
index 7b0d8aedbb..d4ee18edab 100644
--- a/src/analyzer/protocol/bittorrent/BitTorrentTracker.cc
+++ b/src/analyzer/protocol/bittorrent/BitTorrentTracker.cc
@@ -15,7 +15,7 @@
 
 using namespace analyzer::bittorrent;
 
-static TableType* bt_tracker_headers = 0;
+static TableType* bt_tracker_headers = nullptr;
 static RecordType* bittorrent_peer;
 static TableType* bittorrent_peer_set;
 static RecordType* bittorrent_benc_value;
@@ -44,7 +44,7 @@ BitTorrentTracker_Analyzer::BitTorrentTracker_Analyzer(Connection* c)
 	req_buf[sizeof(req_buf) - 1] = 0;
 	req_buf_pos = req_buf;
 	req_buf_len = 0;
-	req_val_uri = 0;
+	req_val_uri = nullptr;
 	req_val_headers = new TableVal({NewRef{}, bt_tracker_headers});
 
 	res_state = BTT_RES_STATUS;
@@ -230,16 +230,16 @@ void BitTorrentTracker_Analyzer::InitBencParser(void)
 	benc_count.clear();
 
 	benc_state = BENC_STATE_EMPTY;
-	benc_raw = 0;
+	benc_raw = nullptr;
 	benc_raw_type = BENC_TYPE_NONE;
 	benc_raw_len = 0;
-	benc_key = 0;
+	benc_key = nullptr;
 	benc_key_len = 0;
-	benc_strlen = 0;
-	benc_str = 0;
+	benc_strlen = nullptr;
+	benc_str = nullptr;
 	benc_str_len = 0;
 	benc_str_have = 0;
-	benc_int = 0;
+	benc_int = nullptr;
 	benc_int_val = 0;
 	}
 
@@ -353,8 +353,8 @@ void BitTorrentTracker_Analyzer::EmitRequest(void)
 			IntrusivePtr{AdoptRef{}, req_val_headers}
 		);
 
-	req_val_uri = 0;
-	req_val_headers = 0;
+	req_val_uri = nullptr;
+	req_val_headers = nullptr;
 	}
 
 bool BitTorrentTracker_Analyzer::ParseResponse(char* line)
@@ -406,7 +406,7 @@ bool BitTorrentTracker_Analyzer::ParseResponse(char* line)
 						IntrusivePtr{AdoptRef{}, val_mgr->GetCount(res_status)},
 						IntrusivePtr{AdoptRef{}, res_val_headers}
 					);
-				res_val_headers = 0;
+				res_val_headers = nullptr;
 				res_buf_pos = res_buf + res_buf_len;
 				res_state = BTT_RES_DONE;
 				}
@@ -481,7 +481,7 @@ void BitTorrentTracker_Analyzer::ResponseBenc(int name_len, char* name,
 			RecordVal* peer = new RecordVal(bittorrent_peer);
 			peer->Assign(0, make_intrusive<AddrVal>(ad));
 			peer->Assign(1, val_mgr->GetPort(pt, TRANSPORT_TCP));
-			res_val_peers->Assign(peer, 0);
+			res_val_peers->Assign(peer, nullptr);
 
 			Unref(peer);
 			}
@@ -617,9 +617,9 @@ int BitTorrentTracker_Analyzer::ResponseParseBenc(void)
 					ResponseBenc(benc_key_len, benc_key,
 							benc_raw_type,
 							benc_raw_len, benc_raw);
-					benc_key = 0;
+					benc_key = nullptr;
 					benc_key_len = 0;
-					benc_raw = 0;
+					benc_raw = nullptr;
 					benc_raw_len = 0;
 					benc_raw_type = BENC_TYPE_NONE;
 					}
@@ -686,7 +686,7 @@ int BitTorrentTracker_Analyzer::ResponseParseBenc(void)
 						ResponseBenc(benc_key_len,
 							benc_key, BENC_TYPE_INT,
 							benc_int_val);
-						benc_key = 0;
+						benc_key = nullptr;
 						benc_key_len = 0;
 						}
 					}
@@ -764,7 +764,7 @@ int BitTorrentTracker_Analyzer::ResponseParseBenc(void)
 							BENC_TYPE_STR,
 							benc_str_len, benc_str);
 					benc_key_len = 0;
-					benc_key = 0;
+					benc_key = nullptr;
 					}
 
 				if ( ! benc_str_len )
@@ -796,7 +796,7 @@ void BitTorrentTracker_Analyzer::EmitResponse(void)
 			IntrusivePtr{AdoptRef{}, res_val_benc}
 		);
 
-	res_val_headers = 0;
-	res_val_peers = 0;
-	res_val_benc = 0;
+	res_val_headers = nullptr;
+	res_val_peers = nullptr;
+	res_val_benc = nullptr;
 	}
diff --git a/src/analyzer/protocol/conn-size/functions.bif b/src/analyzer/protocol/conn-size/functions.bif
index f74464aef9..f6da9c61a8 100644
--- a/src/analyzer/protocol/conn-size/functions.bif
+++ b/src/analyzer/protocol/conn-size/functions.bif
@@ -7,7 +7,7 @@ static analyzer::Analyzer* GetConnsizeAnalyzer(Val* cid)
 	{
 	Connection* c = sessions->FindConnection(cid);
 	if ( ! c )
-		return 0;
+		return nullptr;
 
 	analyzer::Analyzer* a = c->FindAnalyzer("CONNSIZE");
 	if ( ! a )
diff --git a/src/analyzer/protocol/dns/DNS.cc b/src/analyzer/protocol/dns/DNS.cc
index 8ad9d796ce..5c041a09d8 100644
--- a/src/analyzer/protocol/dns/DNS.cc
+++ b/src/analyzer/protocol/dns/DNS.cc
@@ -545,7 +545,7 @@ bool DNS_Interpreter::ParseRR_Name(DNS_MsgInfo* msg,
 
 		default:
 			analyzer->Conn()->Internal("DNS_RR_bad_name");
-			reply_event = 0;
+			reply_event = nullptr;
 	}
 
 	if ( reply_event && ! msg->skip_event )
@@ -757,7 +757,7 @@ bool DNS_Interpreter::ParseRR_TSIG(DNS_MsgInfo* msg,
 	ExtractOctets(data, len, dns_TSIG_addl ? &request_MAC : nullptr);
 	unsigned int orig_id = ExtractShort(data, len);
 	unsigned int rr_error = ExtractShort(data, len);
-	ExtractOctets(data, len, 0);  // Other Data
+	ExtractOctets(data, len, nullptr);  // Other Data
 
 	if ( dns_TSIG_addl )
 		{
@@ -1256,7 +1256,7 @@ static StringVal* extract_char_string(analyzer::Analyzer* analyzer,
                                       const u_char*& data, int& len, int& rdlen)
 	{
 	if ( rdlen <= 0 )
-		return 0;
+		return nullptr;
 
 	uint8_t str_size = data[0];
 
@@ -1267,7 +1267,7 @@ static StringVal* extract_char_string(analyzer::Analyzer* analyzer,
 	if ( str_size > rdlen )
 		{
 		analyzer->Weird("DNS_TXT_char_str_past_rdlen");
-		return 0;
+		return nullptr;
 		}
 
 	StringVal* rval = new StringVal(str_size,
@@ -1428,7 +1428,7 @@ DNS_MsgInfo::DNS_MsgInfo(DNS_RawMsgHdr* hdr, int arg_is_query)
 	id = ntohs(hdr->id);
 	is_query = arg_is_query;
 
-	query_name = 0;
+	query_name = nullptr;
 	atype = TYPE_ALL;
 	aclass = 0;
 	ttl = 0;
@@ -1612,7 +1612,7 @@ Contents_DNS::Contents_DNS(Connection* conn, bool orig,
 	{
 	interp = arg_interp;
 
-	msg_buf = 0;
+	msg_buf = nullptr;
 	buf_n = buf_len = msg_size = 0;
 	state = DNS_LEN_HI;
 	}
@@ -1685,7 +1685,7 @@ void Contents_DNS::DeliverStream(int len, const u_char* data, bool orig)
 		// Haven't filled up the message buffer yet, no more to do.
 		return;
 
-	ForwardPacket(msg_size, msg_buf, orig, -1, 0, 0);
+	ForwardPacket(msg_size, msg_buf, orig, -1, nullptr, 0);
 
 	buf_n = 0;
 	state = DNS_LEN_HI;
@@ -1699,7 +1699,7 @@ DNS_Analyzer::DNS_Analyzer(Connection* conn)
 : tcp::TCP_ApplicationAnalyzer("DNS", conn)
 	{
 	interp = new DNS_Interpreter(this);
-	contents_dns_orig = contents_dns_resp = 0;
+	contents_dns_orig = contents_dns_resp = nullptr;
 
 	if ( Conn()->ConnTransport() == TRANSPORT_TCP )
 		{
diff --git a/src/analyzer/protocol/dns/Plugin.cc b/src/analyzer/protocol/dns/Plugin.cc
index 4aa46499c0..4aceaf0ff4 100644
--- a/src/analyzer/protocol/dns/Plugin.cc
+++ b/src/analyzer/protocol/dns/Plugin.cc
@@ -12,7 +12,7 @@ public:
 	plugin::Configuration Configure() override
 		{
 		AddComponent(new ::analyzer::Component("DNS", ::analyzer::dns::DNS_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("Contents_DNS", 0));
+		AddComponent(new ::analyzer::Component("Contents_DNS", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::DNS";
diff --git a/src/analyzer/protocol/finger/Finger.cc b/src/analyzer/protocol/finger/Finger.cc
index 1beba6947d..6fa54964a3 100644
--- a/src/analyzer/protocol/finger/Finger.cc
+++ b/src/analyzer/protocol/finger/Finger.cc
@@ -60,7 +60,7 @@ void Finger_Analyzer::DeliverStream(int length, const u_char* data, bool is_orig
 		assert(line <= end_of_line);
 		size_t n = end_of_line >= line ? end_of_line - line : 0; // just to be sure if assertions aren't on.
 		const char* at = reinterpret_cast<const char*>(memchr(line, '@', n));
-		const char* host = 0;
+		const char* host = nullptr;
 		if ( ! at )
 			at = host = end_of_line;
 		else
diff --git a/src/analyzer/protocol/ftp/FTP.cc b/src/analyzer/protocol/ftp/FTP.cc
index 7957bb01be..31eaa481d1 100644
--- a/src/analyzer/protocol/ftp/FTP.cc
+++ b/src/analyzer/protocol/ftp/FTP.cc
@@ -204,7 +204,7 @@ void FTP_ADAT_Analyzer::DeliverStream(int len, const u_char* data, bool orig)
 	const char* line = (const char*) data;
 	const char* end_of_line = line + len;
 
-	BroString* decoded_adat = 0;
+	BroString* decoded_adat = nullptr;
 
 	if ( orig )
 		{
@@ -217,7 +217,7 @@ void FTP_ADAT_Analyzer::DeliverStream(int len, const u_char* data, bool orig)
 			{
 			line = skip_whitespace(line + cmd_len, end_of_line);
 			StringVal encoded(end_of_line - line, line);
-			decoded_adat = decode_base64(encoded.AsString(), 0, Conn());
+			decoded_adat = decode_base64(encoded.AsString(), nullptr, Conn());
 
 			if ( first_token )
 				{
@@ -247,7 +247,7 @@ void FTP_ADAT_Analyzer::DeliverStream(int len, const u_char* data, bool orig)
 					// Doesn't look like TLS/SSL, so done analyzing.
 					done = true;
 					delete decoded_adat;
-					decoded_adat = 0;
+					decoded_adat = nullptr;
 					}
 				}
 
@@ -292,7 +292,7 @@ void FTP_ADAT_Analyzer::DeliverStream(int len, const u_char* data, bool orig)
 				{
 				line += 5;
 				StringVal encoded(end_of_line - line, line);
-				decoded_adat = decode_base64(encoded.AsString(), 0, Conn());
+				decoded_adat = decode_base64(encoded.AsString(), nullptr, Conn());
 				}
 
 			break;
diff --git a/src/analyzer/protocol/ftp/Plugin.cc b/src/analyzer/protocol/ftp/Plugin.cc
index 49eef6c281..b7743355a7 100644
--- a/src/analyzer/protocol/ftp/Plugin.cc
+++ b/src/analyzer/protocol/ftp/Plugin.cc
@@ -12,7 +12,7 @@ public:
 	plugin::Configuration Configure() override
 		{
 		AddComponent(new ::analyzer::Component("FTP", ::analyzer::ftp::FTP_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("FTP_ADAT", 0));
+		AddComponent(new ::analyzer::Component("FTP_ADAT", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::FTP";
diff --git a/src/analyzer/protocol/gnutella/Gnutella.cc b/src/analyzer/protocol/gnutella/Gnutella.cc
index e22a5ad755..a6d36218c8 100644
--- a/src/analyzer/protocol/gnutella/Gnutella.cc
+++ b/src/analyzer/protocol/gnutella/Gnutella.cc
@@ -40,7 +40,7 @@ Gnutella_Analyzer::Gnutella_Analyzer(Connection* conn)
 	new_state = 0;
 	sent_establish = 0;
 
-	ms = 0;
+	ms = nullptr;
 
 	orig_msg_state = new GnutellaMsgState();
 	resp_msg_state = new GnutellaMsgState();
diff --git a/src/analyzer/protocol/http/HTTP.cc b/src/analyzer/protocol/http/HTTP.cc
index 14eab65ddc..8b1cf4c415 100644
--- a/src/analyzer/protocol/http/HTTP.cc
+++ b/src/analyzer/protocol/http/HTTP.cc
@@ -48,7 +48,7 @@ HTTP_Entity::HTTP_Entity(HTTP_Message *arg_message, MIME_Entity* parent_entity,
 	header_length = 0;
 	deliver_body = true;
 	encoding = IDENTITY;
-	zip = 0;
+	zip = nullptr;
 	is_partial_content = false;
 	offset = 0;
 	instance_length = -1; // unspecified
@@ -67,7 +67,7 @@ void HTTP_Entity::EndOfData()
 		{
 		zip->Done();
 		delete zip;
-		zip = 0;
+		zip = nullptr;
 		encoding = IDENTITY;
 		}
 
@@ -114,7 +114,7 @@ void HTTP_Entity::Deliver(int len, const char* data, bool trailing_CRLF)
 		switch ( chunked_transfer_state ) {
 		case EXPECT_CHUNK_SIZE:
 			ASSERT(trailing_CRLF);
-			if ( ! atoi_n(len, data, 0, 16, expect_data_length) )
+			if ( ! atoi_n(len, data, nullptr, 16, expect_data_length) )
 				{
 				http_message->Weird("HTTP_bad_chunk_size");
 				expect_data_length = 0;
@@ -365,7 +365,7 @@ void HTTP_Entity::SubmitHeader(mime::MIME_Header* h)
 		if ( ! mime::is_null_data_chunk(vt) )
 			{
 			int64_t n;
-			if ( atoi_n(vt.length, vt.data, 0, 10, n) )
+			if ( atoi_n(vt.length, vt.data, nullptr, 10, n) )
 				{
 				content_length = n;
 
@@ -427,8 +427,8 @@ void HTTP_Entity::SubmitHeader(mime::MIME_Header* h)
 		              instance_length_str.c_str());
 
 		int64_t f, l;
-		atoi_n(first_byte_pos.size(), first_byte_pos.c_str(), 0, 10, f);
-		atoi_n(last_byte_pos.size(), last_byte_pos.c_str(), 0, 10, l);
+		atoi_n(first_byte_pos.size(), first_byte_pos.c_str(), nullptr, 10, f);
+		atoi_n(last_byte_pos.size(), last_byte_pos.c_str(), nullptr, 10, l);
 		int64_t len = l - f + 1;
 
 		if ( DEBUG_http )
@@ -439,7 +439,7 @@ void HTTP_Entity::SubmitHeader(mime::MIME_Header* h)
 			if ( instance_length_str != "*" )
 				{
 				if ( ! atoi_n(instance_length_str.size(),
-				              instance_length_str.c_str(), 0, 10,
+				              instance_length_str.c_str(), nullptr, 10,
 				              instance_length) )
 					instance_length = 0;
 				}
@@ -596,9 +596,9 @@ HTTP_Message::HTTP_Message(HTTP_Analyzer* arg_analyzer,
 	content_line = arg_cl;
 	is_orig = arg_is_orig;
 
-	current_entity = 0;
-	top_level = new HTTP_Entity(this, 0, expect_body);
-	entity_data_buffer = 0;
+	current_entity = nullptr;
+	top_level = new HTTP_Entity(this, nullptr, expect_body);
+	entity_data_buffer = nullptr;
 	BeginEntity(top_level);
 
 	start_time = network_time;
@@ -837,20 +837,20 @@ HTTP_Analyzer::HTTP_Analyzer(Connection* conn)
 	keep_alive = 0;
 	connection_close = 0;
 
-	request_message = reply_message = 0;
+	request_message = reply_message = nullptr;
 	request_state = EXPECT_REQUEST_LINE;
 	reply_state = EXPECT_REPLY_LINE;
 
 	request_ongoing = 0;
-	request_method = request_URI = 0;
-	unescaped_URI = 0;
+	request_method = request_URI = nullptr;
+	unescaped_URI = nullptr;
 
 	reply_ongoing = 0;
 	reply_code = 0;
-	reply_reason_phrase = 0;
+	reply_reason_phrase = nullptr;
 
 	connect_request = false;
-	pia = 0;
+	pia = nullptr;
 	upgraded = false;
 	upgrade_connection = false;
 	upgrade_protocol.clear();
@@ -882,10 +882,10 @@ void HTTP_Analyzer::Done()
 	ReplyMade(true, "message interrupted when connection done");
 
 	delete request_message;
-	request_message = 0;
+	request_message = nullptr;
 
 	delete reply_message;
-	reply_message = 0;
+	reply_message = nullptr;
 
 	GenStats();
 
@@ -1061,8 +1061,8 @@ void HTTP_Analyzer::DeliverStream(int len, const u_char* data, bool is_orig)
 
 				if ( AddChildAnalyzer(pia) )
 					{
-					pia->FirstPacket(true, 0);
-					pia->FirstPacket(false, 0);
+					pia->FirstPacket(true, nullptr);
+					pia->FirstPacket(false, nullptr);
 
 					// This connection has transitioned to no longer
 					// being http and the content line support analyzers
@@ -1073,7 +1073,7 @@ void HTTP_Analyzer::DeliverStream(int len, const u_char* data, bool is_orig)
 
 				else
 					// AddChildAnalyzer() will have deleted PIA.
-					pia = 0;
+					pia = nullptr;
 				}
 
 			break;
@@ -1193,7 +1193,7 @@ const char* HTTP_Analyzer::PrefixMatch(const char* line,
 
 	if ( *prefix )
 		// It didn't match.
-		return 0;
+		return nullptr;
 
 	return line;
 	}
@@ -1201,15 +1201,15 @@ const char* HTTP_Analyzer::PrefixMatch(const char* line,
 const char* HTTP_Analyzer::PrefixWordMatch(const char* line,
 				const char* end_of_line, const char* prefix)
 	{
-	if ( (line = PrefixMatch(line, end_of_line, prefix)) == 0 )
-		return 0;
+	if ( (line = PrefixMatch(line, end_of_line, prefix)) == nullptr )
+		return nullptr;
 
 	const char* orig_line = line;
 	line = skip_whitespace(line, end_of_line);
 
 	if ( line == orig_line )
 		// Word didn't end at prefix.
-		return 0;
+		return nullptr;
 
 	return line;
 	}
@@ -1235,7 +1235,7 @@ static const char* get_HTTP_token(const char* s, const char* e)
 
 int HTTP_Analyzer::HTTP_RequestLine(const char* line, const char* end_of_line)
 	{
-	const char* rest = 0;
+	const char* rest = nullptr;
 	const char* end_of_method = get_HTTP_token(line, end_of_line);
 
 	if ( end_of_method == line )
@@ -1439,7 +1439,7 @@ void HTTP_Analyzer::HTTP_Reply()
 	else
 		{
 		Unref(reply_reason_phrase);
-		reply_reason_phrase = 0;
+		reply_reason_phrase = nullptr;
 		}
 	}
 
@@ -1459,7 +1459,7 @@ void HTTP_Analyzer::RequestMade(bool interrupted, const char* msg)
 	Unref(unescaped_URI);
 	Unref(request_URI);
 
-	request_method = request_URI = unescaped_URI = 0;
+	request_method = request_URI = unescaped_URI = nullptr;
 
 	num_request_lines = 0;
 
@@ -1492,7 +1492,7 @@ void HTTP_Analyzer::ReplyMade(bool interrupted, const char* msg)
 	if ( reply_reason_phrase )
 		{
 		Unref(reply_reason_phrase);
-		reply_reason_phrase = 0;
+		reply_reason_phrase = nullptr;
 		}
 
 	// unanswered requests = 1 because there is no pop after 101.
@@ -1531,7 +1531,7 @@ void HTTP_Analyzer::RequestClash(Val* /* clash_val */)
 
 const BroString* HTTP_Analyzer::UnansweredRequestMethod()
 	{
-	return unanswered_requests.empty() ? 0 : unanswered_requests.front()->AsString();
+	return unanswered_requests.empty() ? nullptr : unanswered_requests.front()->AsString();
 	}
 
 int HTTP_Analyzer::HTTP_ReplyLine(const char* line, const char* end_of_line)
diff --git a/src/analyzer/protocol/icmp/ICMP.cc b/src/analyzer/protocol/icmp/ICMP.cc
index 59e8d93909..552f87c947 100644
--- a/src/analyzer/protocol/icmp/ICMP.cc
+++ b/src/analyzer/protocol/icmp/ICMP.cc
@@ -81,7 +81,7 @@ void ICMP_Analyzer::DeliverPacket(int len, const u_char* data,
 	if ( rule_matcher )
 		{
 		if ( ! matcher_state.MatcherInitialized(is_orig) )
-			matcher_state.InitEndpointMatcher(this, ip, len, is_orig, 0);
+			matcher_state.InitEndpointMatcher(this, ip, len, is_orig, nullptr);
 		}
 
 	type = icmpp->icmp_type;
@@ -497,7 +497,7 @@ void ICMP_Analyzer::Echo(double t, const struct icmp* icmpp, int len,
 					 int caplen, const u_char*& data, const IP_Hdr* ip_hdr)
 	{
 	// For handling all Echo related ICMP messages
-	EventHandlerPtr f = 0;
+	EventHandlerPtr f = nullptr;
 
 	if ( ip_hdr->NextProto() == IPPROTO_ICMPV6 )
 		f = (icmpp->icmp_type == ICMP6_ECHO_REQUEST)
@@ -658,7 +658,7 @@ void ICMP_Analyzer::RouterSolicit(double t, const struct icmp* icmpp, int len,
 void ICMP_Analyzer::Context4(double t, const struct icmp* icmpp,
 		int len, int caplen, const u_char*& data, const IP_Hdr* ip_hdr)
 	{
-	EventHandlerPtr f = 0;
+	EventHandlerPtr f = nullptr;
 
 	switch ( icmpp->icmp_type )
 		{
@@ -684,7 +684,7 @@ void ICMP_Analyzer::Context4(double t, const struct icmp* icmpp,
 void ICMP_Analyzer::Context6(double t, const struct icmp* icmpp,
 		int len, int caplen, const u_char*& data, const IP_Hdr* ip_hdr)
 	{
-	EventHandlerPtr f = 0;
+	EventHandlerPtr f = nullptr;
 
 	switch ( icmpp->icmp_type )
 		{
@@ -720,8 +720,8 @@ void ICMP_Analyzer::Context6(double t, const struct icmp* icmpp,
 
 VectorVal* ICMP_Analyzer::BuildNDOptionsVal(int caplen, const u_char* data)
 	{
-	static RecordType* icmp6_nd_option_type = 0;
-	static RecordType* icmp6_nd_prefix_info_type = 0;
+	static RecordType* icmp6_nd_option_type = nullptr;
+	static RecordType* icmp6_nd_prefix_info_type = nullptr;
 
 	if ( ! icmp6_nd_option_type )
 		{
diff --git a/src/analyzer/protocol/ident/Ident.cc b/src/analyzer/protocol/ident/Ident.cc
index 5417492f58..a9c6d5a066 100644
--- a/src/analyzer/protocol/ident/Ident.cc
+++ b/src/analyzer/protocol/ident/Ident.cc
@@ -52,7 +52,7 @@ void Ident_Analyzer::DeliverStream(int length, const u_char* data, bool is_orig)
 	const char* orig_line = line;
 	const char* end_of_line = line + length;
 
-	tcp::TCP_Endpoint* s = 0;
+	tcp::TCP_Endpoint* s = nullptr;
 
 	if ( TCP() )
 		s = is_orig ? TCP()->Orig() : TCP()->Resp();
@@ -194,17 +194,17 @@ const char* Ident_Analyzer::ParsePair(const char* line, const char* end_of_line,
 	line = ParsePort(line, end_of_line, p1);
 	if ( ! line )
 		{
-		return 0;
+		return nullptr;
 		}
 
 	if ( line >= end_of_line || line[0] != ',' )
-		return 0;
+		return nullptr;
 
 	++line;
 
 	line = ParsePort(line, end_of_line, p2);
 	if ( ! line )
-		return 0;
+		return nullptr;
 
 	return line;
 	}
@@ -216,7 +216,7 @@ const char* Ident_Analyzer::ParsePort(const char* line, const char* end_of_line,
 
 	line = skip_whitespace(line, end_of_line);
 	if ( ! isdigit(*line) )
-		return 0;
+		return nullptr;
 
 	const char* l = line;
 
diff --git a/src/analyzer/protocol/irc/IRC.cc b/src/analyzer/protocol/irc/IRC.cc
index ff9bb4cb4c..258ae51086 100644
--- a/src/analyzer/protocol/irc/IRC.cc
+++ b/src/analyzer/protocol/irc/IRC.cc
@@ -277,7 +277,7 @@ void IRC_Analyzer::DeliverStream(int length, const u_char* line, bool orig)
 				if ( parts[i][0] == '@' )
 					parts[i] = parts[i].substr(1);
 				auto idx = make_intrusive<StringVal>(parts[i].c_str());
-				set->Assign(idx.get(), 0);
+				set->Assign(idx.get(), nullptr);
 				}
 
 			EnqueueConnEvent(irc_names_info,
@@ -468,7 +468,7 @@ void IRC_Analyzer::DeliverStream(int length, const u_char* line, bool orig)
 			for ( unsigned int i = 0; i < parts.size(); ++i )
 				{
 				auto idx = make_intrusive<StringVal>(parts[i].c_str());
-				set->Assign(idx.get(), 0);
+				set->Assign(idx.get(), nullptr);
 				}
 
 			EnqueueConnEvent(irc_whois_channel_line,
@@ -857,7 +857,7 @@ void IRC_Analyzer::DeliverStream(int length, const u_char* line, bool orig)
 				info->Assign(2, make_intrusive<StringVal>(empty_string.c_str()));
 			// User mode.
 			info->Assign(3, make_intrusive<StringVal>(empty_string.c_str()));
-			list->Assign(info, 0);
+			list->Assign(info, nullptr);
 			Unref(info);
 			}
 
@@ -918,7 +918,7 @@ void IRC_Analyzer::DeliverStream(int length, const u_char* line, bool orig)
 			info->Assign(2, make_intrusive<StringVal>(empty_string.c_str()));
 			// User mode:
 			info->Assign(3, make_intrusive<StringVal>(mode.c_str()));
-			list->Assign(info.get(), 0);
+			list->Assign(info.get(), nullptr);
 			}
 
 		EnqueueConnEvent(irc_join_message,
@@ -957,7 +957,7 @@ void IRC_Analyzer::DeliverStream(int length, const u_char* line, bool orig)
 		for ( unsigned int i = 0; i < channelList.size(); ++i )
 			{
 			auto idx = make_intrusive<StringVal>(channelList[i].c_str());
-			set->Assign(idx.get(), 0);
+			set->Assign(idx.get(), nullptr);
 			}
 
 		EnqueueConnEvent(irc_part_message,
diff --git a/src/analyzer/protocol/login/Login.cc b/src/analyzer/protocol/login/Login.cc
index 39767ca420..d3dfee53f9 100644
--- a/src/analyzer/protocol/login/Login.cc
+++ b/src/analyzer/protocol/login/Login.cc
@@ -16,7 +16,7 @@
 
 using namespace analyzer::login;
 
-static RE_Matcher* re_skip_authentication = 0;
+static RE_Matcher* re_skip_authentication = nullptr;
 static RE_Matcher* re_direct_login_prompts;
 static RE_Matcher* re_login_prompts;
 static RE_Matcher* re_login_non_failure_msgs;
@@ -39,7 +39,7 @@ Login_Analyzer::Login_Analyzer(const char* name, Connection* conn)
 	user_text_first = 0;
 	user_text_last = MAX_USER_TEXT - 1;
 	num_user_text = 0;
-	client_name = username = 0;
+	client_name = username = nullptr;
 	saw_ploy = is_VMS = false;
 
 	if ( ! re_skip_authentication )
@@ -214,7 +214,7 @@ void Login_Analyzer::AuthenticationDialog(bool orig, char* line)
 			 // respect to it (see below).
 			 login_prompt_line != failure_line);
 
-		const char* next_prompt = 0;
+		const char* next_prompt = nullptr;
 		while ( (*prompt != '\0' &&
 			 (next_prompt = IsLoginPrompt(prompt + 1))) ||
 			multi_line_prompt )
@@ -507,7 +507,7 @@ const char* Login_Analyzer::IsLoginPrompt(const char* line) const
 	int prompt_match = re_login_prompts->MatchAnywhere(line);
 	if ( ! prompt_match || IsFailureMsg(line) )
 		// IRIX can report "login: ERROR: Login incorrect"
-		return 0;
+		return nullptr;
 
 	return &line[prompt_match];
 	}
@@ -565,7 +565,7 @@ char* Login_Analyzer::PeekUserText()
 		{
 		reporter->AnalyzerError(this,
 		  "underflow in Login_Analyzer::PeekUserText()");
-		return 0;
+		return nullptr;
 		}
 
 	return user_text[user_text_first];
@@ -576,7 +576,7 @@ char* Login_Analyzer::PopUserText()
 	char* s = PeekUserText();
 
 	if ( ! s )
-		return 0;
+		return nullptr;
 
 	if ( ++user_text_first == MAX_USER_TEXT )
 		user_text_first = 0;
diff --git a/src/analyzer/protocol/login/NVT.cc b/src/analyzer/protocol/login/NVT.cc
index 89295e1ac2..096adca591 100644
--- a/src/analyzer/protocol/login/NVT.cc
+++ b/src/analyzer/protocol/login/NVT.cc
@@ -320,7 +320,7 @@ char* TelnetEnvironmentOption::ExtractEnv(u_char*& data, int& len, int& code)
 
 	if ( code != ENVIRON_VAR && code != ENVIRON_VAL &&
 	     code != ENVIRON_USERVAR )
-		return 0;
+		return nullptr;
 
 	// Move past code.
 	--len;
@@ -338,7 +338,7 @@ char* TelnetEnvironmentOption::ExtractEnv(u_char*& data, int& len, int& code)
 			{
 			++d;	// move past ESC
 			if ( d >= data_end )
-				return 0;
+				return nullptr;
 			break;
 			}
 		}
@@ -400,7 +400,7 @@ TelnetOption* NVT_Analyzer::FindOption(unsigned int code)
 		if ( options[i]->Code() == code )
 			return options[i];
 
-	TelnetOption* opt = 0;
+	TelnetOption* opt = nullptr;
 	if ( i < NUM_TELNET_OPTIONS )
 		{ // Maybe we haven't created this option yet.
 		switch ( code ) {
diff --git a/src/analyzer/protocol/login/Plugin.cc b/src/analyzer/protocol/login/Plugin.cc
index aeedd5c04d..27457b04d7 100644
--- a/src/analyzer/protocol/login/Plugin.cc
+++ b/src/analyzer/protocol/login/Plugin.cc
@@ -17,10 +17,10 @@ public:
 		AddComponent(new ::analyzer::Component("Telnet", ::analyzer::login::Telnet_Analyzer::Instantiate));
 		AddComponent(new ::analyzer::Component("Rsh", ::analyzer::login::Rsh_Analyzer::Instantiate));
 		AddComponent(new ::analyzer::Component("Rlogin", ::analyzer::login::Rlogin_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("NVT", 0));
-		AddComponent(new ::analyzer::Component("Login", 0));
-		AddComponent(new ::analyzer::Component("Contents_Rsh", 0));
-		AddComponent(new ::analyzer::Component("Contents_Rlogin", 0));
+		AddComponent(new ::analyzer::Component("NVT", nullptr));
+		AddComponent(new ::analyzer::Component("Login", nullptr));
+		AddComponent(new ::analyzer::Component("Contents_Rsh", nullptr));
+		AddComponent(new ::analyzer::Component("Contents_Rlogin", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::Login";
diff --git a/src/analyzer/protocol/login/Rlogin.cc b/src/analyzer/protocol/login/Rlogin.cc
index e041d757c9..244deb9cba 100644
--- a/src/analyzer/protocol/login/Rlogin.cc
+++ b/src/analyzer/protocol/login/Rlogin.cc
@@ -16,7 +16,7 @@ Contents_Rlogin_Analyzer::Contents_Rlogin_Analyzer(Connection* conn, bool orig,
 	{
 	num_bytes_to_scan = 0;
 	analyzer = arg_analyzer;
-	peer = 0;
+	peer = nullptr;
 
 	if ( orig )
 		state = save_state = RLOGIN_FIRST_NULL;
diff --git a/src/analyzer/protocol/mime/MIME.cc b/src/analyzer/protocol/mime/MIME.cc
index ea689733de..d644f00bb0 100644
--- a/src/analyzer/protocol/mime/MIME.cc
+++ b/src/analyzer/protocol/mime/MIME.cc
@@ -21,7 +21,7 @@
 
 namespace analyzer { namespace mime {
 
-static const data_chunk_t null_data_chunk = { 0, 0 };
+static const data_chunk_t null_data_chunk = { 0, nullptr };
 
 int mime_header_only = 0;
 int mime_decode_data = 1;
@@ -65,14 +65,14 @@ enum MIME_BOUNDARY_DELIMITER {
 static const char* MIMEHeaderName[] = {
 	"content-type",
 	"content-transfer-encoding",
-	0,
+	nullptr,
 };
 
 static const char* MIMEContentTypeName[] = {
 	"MULTIPART",
 	"MESSAGE",
 	"TEXT",
-	0,
+	nullptr,
 };
 
 static const char* MIMEContentSubtypeName[] = {
@@ -86,7 +86,7 @@ static const char* MIMEContentSubtypeName[] = {
 
 	"PLAIN",		// for text
 
-	0,			// other
+	nullptr,			// other
 };
 
 static const char* MIMEContentEncodingName[] = {
@@ -95,12 +95,12 @@ static const char* MIMEContentEncodingName[] = {
 	"BINARY",
 	"QUOTED-PRINTABLE",
 	"BASE64",
-	0,
+	nullptr,
 };
 
 bool is_null_data_chunk(data_chunk_t b)
 	{
-	return b.data == 0;
+	return b.data == nullptr;
 	}
 
 bool is_lws(char ch)
@@ -437,7 +437,7 @@ using namespace analyzer::mime;
 
 MIME_Multiline::MIME_Multiline()
 	{
-	line = 0;
+	line = nullptr;
 	}
 
 MIME_Multiline::~MIME_Multiline()
@@ -454,7 +454,7 @@ void MIME_Multiline::append(int len, const char* data)
 BroString* MIME_Multiline::get_concatenated_line()
 	{
 	if ( buffer.empty() )
-		return 0;
+		return nullptr;
 
 	delete line;
 	line = concatenate(buffer);
@@ -546,7 +546,7 @@ void MIME_Entity::init()
 	in_header = 1;
 	end_of_data = 0;
 
-	current_header_line = 0;
+	current_header_line = nullptr;
 	current_field_type = MIME_FIELD_OTHER;
 
 	need_to_parse_parameters = 0;
@@ -554,22 +554,22 @@ void MIME_Entity::init()
 	content_type_str = new StringVal("TEXT");
 	content_subtype_str = new StringVal("PLAIN");
 
-	content_encoding_str = 0;
-	multipart_boundary = 0;
+	content_encoding_str = nullptr;
+	multipart_boundary = nullptr;
 	content_type = CONTENT_TYPE_TEXT;
 	content_subtype = CONTENT_SUBTYPE_PLAIN;
 	content_encoding = CONTENT_ENCODING_OTHER;
 
-	parent = 0;
-	current_child_entity = 0;
+	parent = nullptr;
+	current_child_entity = nullptr;
 
-	base64_decoder = 0;
+	base64_decoder = nullptr;
 
 	data_buf_length = 0;
-	data_buf_data = 0;
+	data_buf_data = nullptr;
 	data_buf_offset = -1;
 
-	message = 0;
+	message = nullptr;
 	delay_adding_implicit_CRLF = false;
 	want_all_headers = false;
 	}
@@ -577,7 +577,7 @@ void MIME_Entity::init()
 MIME_Entity::~MIME_Entity()
 	{
 	if ( ! end_of_data )
-		reporter->AnalyzerError(message ? message->GetAnalyzer() : 0,
+		reporter->AnalyzerError(message ? message->GetAnalyzer() : nullptr,
 		            "missing MIME_Entity::EndOfData() before ~MIME_Entity");
 
 	delete current_header_line;
@@ -653,7 +653,7 @@ void MIME_Entity::EndOfData()
 
 	else
 		{
-		if ( current_child_entity != 0 )
+		if ( current_child_entity != nullptr )
 			{
 			if ( content_type == CONTENT_TYPE_MULTIPART )
 				IllegalFormat("multipart closing boundary delimiter missing");
@@ -675,13 +675,13 @@ void MIME_Entity::NewDataLine(int len, const char* data, bool trailing_CRLF)
 		{
 		switch ( CheckBoundaryDelimiter(len, data) ) {
 			case MULTIPART_BOUNDARY:
-				if ( current_child_entity != 0 )
+				if ( current_child_entity != nullptr )
 					EndChildEntity();
 				BeginChildEntity();
 				return;
 
 			case MULTIPART_CLOSING_BOUNDARY:
-				if ( current_child_entity != 0 )
+				if ( current_child_entity != nullptr )
 					EndChildEntity();
 				EndOfData();
 				return;
@@ -695,7 +695,7 @@ void MIME_Entity::NewDataLine(int len, const char* data, bool trailing_CRLF)
 		// binary encoding, and thus do not need to decode
 		// before passing the data to child.
 
-		if ( current_child_entity != 0 )
+		if ( current_child_entity != nullptr )
 			// Data before the first or after the last
 			// boundary delimiter are ignored
 			current_child_entity->Deliver(len, data, trailing_CRLF);
@@ -722,7 +722,7 @@ void MIME_Entity::NewHeader(int len, const char* data)
 
 void MIME_Entity::ContHeader(int len, const char* data)
 	{
-	if ( current_header_line == 0 )
+	if ( current_header_line == nullptr )
 		{
 		IllegalFormat("first header line starts with linear whitespace");
 
@@ -737,11 +737,11 @@ void MIME_Entity::ContHeader(int len, const char* data)
 
 void MIME_Entity::FinishHeader()
 	{
-	if ( current_header_line == 0 )
+	if ( current_header_line == nullptr )
 		return;
 
 	MIME_Header* h = new MIME_Header(current_header_line);
-	current_header_line = 0;
+	current_header_line = nullptr;
 
 	if ( ! is_null_data_chunk(h->get_name()) )
 		{
@@ -762,7 +762,7 @@ int MIME_Entity::LookupMIMEHeaderName(data_chunk_t name)
 	// A linear lookup should be fine for now.
 	// header names are case-insensitive (RFC 822, 2822, 2045).
 
-	for ( int i = 0; MIMEHeaderName[i] != 0; ++i )
+	for ( int i = 0; MIMEHeaderName[i] != nullptr; ++i )
 		if ( istrequal(name, MIMEHeaderName[i]) )
 			return i;
 	return -1;
@@ -770,7 +770,7 @@ int MIME_Entity::LookupMIMEHeaderName(data_chunk_t name)
 
 void MIME_Entity::ParseMIMEHeader(MIME_Header* h)
 	{
-	if ( h == 0 )
+	if ( h == nullptr )
 		return;
 
 	current_field_type = LookupMIMEHeaderName(h->get_name());
@@ -884,7 +884,7 @@ bool MIME_Entity::ParseFieldParameters(int len, const char* data)
 		data += offset;
 		len -= offset;
 
-		BroString* val = 0;
+		BroString* val = nullptr;
 
 		if ( current_field_type == MIME_CONTENT_TYPE &&
 		     content_type == CONTENT_TYPE_MULTIPART &&
@@ -1172,13 +1172,13 @@ void MIME_Entity::FinishDecodeBase64()
 		}
 
 	delete base64_decoder;
-	base64_decoder = 0;
+	base64_decoder = nullptr;
 	}
 
 bool MIME_Entity::GetDataBuffer()
 	{
 	int ret = message->RequestBuffer(&data_buf_length, &data_buf_data);
-	if ( ! ret || data_buf_length == 0 || data_buf_data == 0 )
+	if ( ! ret || data_buf_length == 0 || data_buf_data == nullptr )
 		{
 		// reporter->InternalError("cannot get data buffer from MIME_Message", "");
 		return false;
@@ -1250,18 +1250,18 @@ void MIME_Entity::SubmitAllHeaders()
 
 void MIME_Entity::BeginChildEntity()
 	{
-	ASSERT(current_child_entity == 0);
+	ASSERT(current_child_entity == nullptr);
 	current_child_entity = NewChildEntity();
 	message->BeginEntity(current_child_entity);
 	}
 
 void MIME_Entity::EndChildEntity()
 	{
-	ASSERT(current_child_entity != 0);
+	ASSERT(current_child_entity != nullptr);
 
 	current_child_entity->EndOfData();
 	delete current_child_entity;
-	current_child_entity = 0;
+	current_child_entity = nullptr;
 	}
 
 void MIME_Entity::IllegalFormat(const char* explanation)
@@ -1349,7 +1349,7 @@ MIME_Mail::MIME_Mail(analyzer::Analyzer* mail_analyzer, bool orig, int buf_size)
 
 	content_hash_length = 0;
 
-	top_level = new MIME_Entity(this, 0);	// to be changed to MIME_Mail
+	top_level = new MIME_Entity(this, nullptr);	// to be changed to MIME_Mail
 	BeginEntity(top_level);
 	}
 
diff --git a/src/analyzer/protocol/mime/MIME.h b/src/analyzer/protocol/mime/MIME.h
index e07954063c..eb8c75a581 100644
--- a/src/analyzer/protocol/mime/MIME.h
+++ b/src/analyzer/protocol/mime/MIME.h
@@ -188,7 +188,7 @@ public:
 		// Cannot initialize top_level entity because we do
 		// not know its type yet (MIME_Entity / MIME_Mail /
 		// etc.).
-		top_level = 0;
+		top_level = nullptr;
 		finished = false;
 		analyzer = arg_analyzer;
 		}
diff --git a/src/analyzer/protocol/ncp/NCP.cc b/src/analyzer/protocol/ncp/NCP.cc
index 03580d2abb..08ff6d5ac3 100644
--- a/src/analyzer/protocol/ncp/NCP.cc
+++ b/src/analyzer/protocol/ncp/NCP.cc
@@ -83,7 +83,7 @@ void NCP_Session::DeliverFrame(const binpac::NCP::ncp_frame* frame)
 FrameBuffer::FrameBuffer(size_t header_length)
 	{
 	hdr_len = header_length;
-	msg_buf = 0;
+	msg_buf = nullptr;
 	buf_len = 0;
 	Reset();
 	}
diff --git a/src/analyzer/protocol/ncp/Plugin.cc b/src/analyzer/protocol/ncp/Plugin.cc
index 9f17881f1b..b76fcbf748 100644
--- a/src/analyzer/protocol/ncp/Plugin.cc
+++ b/src/analyzer/protocol/ncp/Plugin.cc
@@ -12,7 +12,7 @@ public:
 	plugin::Configuration Configure() override
 		{
 		AddComponent(new ::analyzer::Component("NCP", ::analyzer::ncp::NCP_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("Contents_NCP", 0));
+		AddComponent(new ::analyzer::Component("Contents_NCP", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::NCP";
diff --git a/src/analyzer/protocol/netbios/NetbiosSSN.cc b/src/analyzer/protocol/netbios/NetbiosSSN.cc
index 31b662d4e6..3af2569738 100644
--- a/src/analyzer/protocol/netbios/NetbiosSSN.cc
+++ b/src/analyzer/protocol/netbios/NetbiosSSN.cc
@@ -214,7 +214,7 @@ int NetbiosSSN_Interpreter::ConvertName(const u_char* name, int name_len,
 	{
 	// Taken from tcpdump's smbutil.c.
 
-	xname = 0;
+	xname = nullptr;
 
 	if ( name_len < 1 )
 		return 0;
@@ -340,7 +340,7 @@ Contents_NetbiosSSN::Contents_NetbiosSSN(Connection* conn, bool orig,
 	{
 	interp = arg_interp;
 	type = flags = msg_size = 0;
-	msg_buf = 0;
+	msg_buf = nullptr;
 	buf_n = buf_len = msg_size = 0;
 	state = NETBIOS_SSN_TYPE;
 	}
@@ -455,7 +455,7 @@ NetbiosSSN_Analyzer::NetbiosSSN_Analyzer(Connection* conn)
 	{
 	//smb_session = new SMB_Session(this);
 	interp = new NetbiosSSN_Interpreter(this);
-	orig_netbios = resp_netbios = 0;
+	orig_netbios = resp_netbios = nullptr;
 	did_session_done = 0;
 
 	if ( Conn()->ConnTransport() == TRANSPORT_TCP )
diff --git a/src/analyzer/protocol/netbios/Plugin.cc b/src/analyzer/protocol/netbios/Plugin.cc
index dde55af51f..47db030464 100644
--- a/src/analyzer/protocol/netbios/Plugin.cc
+++ b/src/analyzer/protocol/netbios/Plugin.cc
@@ -12,7 +12,7 @@ public:
 	plugin::Configuration Configure() override
 		{
 		AddComponent(new ::analyzer::Component("NetbiosSSN", ::analyzer::netbios_ssn::NetbiosSSN_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("Contents_NetbiosSSN", 0));
+		AddComponent(new ::analyzer::Component("Contents_NetbiosSSN", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::NetBIOS";
diff --git a/src/analyzer/protocol/pia/PIA.cc b/src/analyzer/protocol/pia/PIA.cc
index f57771e708..5845f7d540 100644
--- a/src/analyzer/protocol/pia/PIA.cc
+++ b/src/analyzer/protocol/pia/PIA.cc
@@ -22,7 +22,7 @@ PIA::~PIA()
 
 void PIA::ClearBuffer(Buffer* buffer)
 	{
-	DataBlock* next = 0;
+	DataBlock* next = nullptr;
 	for ( DataBlock* b = buffer->head; b; b = next )
 		{
 		next = b->next;
@@ -31,14 +31,14 @@ void PIA::ClearBuffer(Buffer* buffer)
 		delete b;
 		}
 
-	buffer->head = buffer->tail = 0;
+	buffer->head = buffer->tail = nullptr;
 	buffer->size = 0;
 	}
 
 void PIA::AddToBuffer(Buffer* buffer, uint64_t seq, int len, const u_char* data,
 			bool is_orig, const IP_Hdr* ip)
 	{
-	u_char* tmp = 0;
+	u_char* tmp = nullptr;
 
 	if ( data )
 		{
@@ -47,12 +47,12 @@ void PIA::AddToBuffer(Buffer* buffer, uint64_t seq, int len, const u_char* data,
 		}
 
 	DataBlock* b = new DataBlock;
-	b->ip = ip ? ip->Copy() : 0;
+	b->ip = ip ? ip->Copy() : nullptr;
 	b->data = tmp;
 	b->is_orig = is_orig;
 	b->len = len;
 	b->seq = seq;
-	b->next = 0;
+	b->next = nullptr;
 
 	if ( buffer->tail )
 		{
@@ -117,14 +117,14 @@ void PIA::PIA_DeliverPacket(int len, const u_char* data, bool is_orig, uint64_t
 
 	pkt_buffer.state = new_state;
 
-	current_packet.data = 0;
+	current_packet.data = nullptr;
 	}
 
 void PIA::Match(Rule::PatternType type, const u_char* data, int len,
 		bool is_orig, bool bol, bool eol, bool clear_state)
 	{
 	if ( ! MatcherInitialized(is_orig) )
-		InitEndpointMatcher(AsAnalyzer(), 0, 0, is_orig, this);
+		InitEndpointMatcher(AsAnalyzer(), nullptr, 0, is_orig, this);
 
 	RuleMatcherState::Match(type, data, len, is_orig, bol, eol, clear_state);
 	}
@@ -207,9 +207,9 @@ void PIA_TCP::Init()
 void PIA_TCP::FirstPacket(bool is_orig, const IP_Hdr* ip)
 	{
 	static char dummy_packet[sizeof(struct ip) + sizeof(struct tcphdr)];
-	static struct ip* ip4 = 0;
-	static struct tcphdr* tcp4 = 0;
-	static IP_Hdr* ip4_hdr = 0;
+	static struct ip* ip4 = nullptr;
+	static struct tcphdr* tcp4 = nullptr;
+	static IP_Hdr* ip4_hdr = nullptr;
 
 	DBG_LOG(DBG_ANALYZER, "PIA_TCP[%d] FirstPacket(%s)", GetID(), (is_orig ? "T" : "F"));
 
@@ -277,7 +277,7 @@ void PIA_TCP::DeliverStream(int len, const u_char* data, bool is_orig)
 						SKIPPING : MATCHING_ONLY;
 		}
 
-	DoMatch(data, len, is_orig, false, false, false, 0);
+	DoMatch(data, len, is_orig, false, false, false, nullptr);
 
 	stream_buffer.state = new_state;
 	}
@@ -288,7 +288,7 @@ void PIA_TCP::Undelivered(uint64_t seq, int len, bool is_orig)
 
 	if ( stream_buffer.state == BUFFERING )
 		// We use data=nil to mark an undelivered.
-		AddToBuffer(&stream_buffer, seq, len, 0, is_orig);
+		AddToBuffer(&stream_buffer, seq, len, nullptr, is_orig);
 
 	// No check for buffer overrun here. I think that's ok.
 	}
diff --git a/src/analyzer/protocol/pia/PIA.h b/src/analyzer/protocol/pia/PIA.h
index 467d353464..575cb89571 100644
--- a/src/analyzer/protocol/pia/PIA.h
+++ b/src/analyzer/protocol/pia/PIA.h
@@ -25,7 +25,7 @@ public:
 	// Called when PIA wants to put an Analyzer in charge.  rule is the
 	// signature that triggered the activitation, if any.
 	virtual void ActivateAnalyzer(analyzer::Tag tag,
-					const Rule* rule = 0) = 0;
+					const Rule* rule = nullptr) = 0;
 
 	// Called when PIA wants to remove an Analyzer.
 	virtual void DeactivateAnalyzer(analyzer::Tag tag) = 0;
@@ -58,7 +58,7 @@ protected:
 	};
 
 	struct Buffer {
-		Buffer() { head = tail = 0; size = 0; state = INIT; }
+		Buffer() { head = tail = nullptr; size = 0; state = INIT; }
 
 		DataBlock* head;
 		DataBlock* tail;
@@ -67,15 +67,15 @@ protected:
 	};
 
 	void AddToBuffer(Buffer* buffer, uint64_t seq, int len,
-				const u_char* data, bool is_orig, const IP_Hdr* ip = 0);
+				const u_char* data, bool is_orig, const IP_Hdr* ip = nullptr);
 	void AddToBuffer(Buffer* buffer, int len,
-				const u_char* data, bool is_orig, const IP_Hdr* ip = 0);
+				const u_char* data, bool is_orig, const IP_Hdr* ip = nullptr);
 	void ClearBuffer(Buffer* buffer);
 
 	DataBlock* CurrentPacket()	{ return &current_packet; }
 
 	void DoMatch(const u_char* data, int len, bool is_orig, bool bol,
-			bool eol, bool clear_state, const IP_Hdr* ip = 0);
+			bool eol, bool clear_state, const IP_Hdr* ip = nullptr);
 
 	void SetConn(Connection* c)	{ conn = c; }
 
@@ -161,7 +161,7 @@ protected:
 	void Undelivered(uint64_t seq, int len, bool is_orig) override;
 
 	void ActivateAnalyzer(analyzer::Tag tag,
-					const Rule* rule = 0) override;
+					const Rule* rule = nullptr) override;
 	void DeactivateAnalyzer(analyzer::Tag tag) override;
 
 private:
diff --git a/src/analyzer/protocol/pop3/POP3.cc b/src/analyzer/protocol/pop3/POP3.cc
index c5e2d9bb1f..174d11b826 100644
--- a/src/analyzer/protocol/pop3/POP3.cc
+++ b/src/analyzer/protocol/pop3/POP3.cc
@@ -43,7 +43,7 @@ POP3_Analyzer::POP3_Analyzer(Connection* conn)
 	lastRequiredCommand = 0;
 	authLines = 0;
 
-	mail = 0;
+	mail = nullptr;
 
 	cl_orig = new tcp::ContentLine_Analyzer(conn, true);
 	AddSupportAnalyzer(cl_orig);
@@ -136,7 +136,7 @@ void POP3_Analyzer::ProcessRequest(int length, const char* line)
 		++authLines;
 
 		BroString encoded(line);
-		BroString* decoded = decode_base64(&encoded, 0, Conn());
+		BroString* decoded = decode_base64(&encoded, nullptr, Conn());
 
 		if ( ! decoded )
 			{
@@ -854,7 +854,7 @@ void POP3_Analyzer::EndData()
 		{
 		mail->Done();
 		delete mail;
-		mail = 0;
+		mail = nullptr;
 		}
 	}
 
diff --git a/src/analyzer/protocol/pop3/POP3.h b/src/analyzer/protocol/pop3/POP3.h
index 827407d61b..8d3db050df 100644
--- a/src/analyzer/protocol/pop3/POP3.h
+++ b/src/analyzer/protocol/pop3/POP3.h
@@ -103,7 +103,7 @@ protected:
 	int ParseCmd(string cmd);
 	void AuthSuccessfull();
 	void POP3Event(EventHandlerPtr event, bool is_orig,
-			const char* arg1 = 0, const char* arg2 = 0);
+			const char* arg1 = nullptr, const char* arg2 = nullptr);
 
 	mime::MIME_Mail* mail;
 	list<string> cmds;
diff --git a/src/analyzer/protocol/rdp/RDP.cc b/src/analyzer/protocol/rdp/RDP.cc
index 7deaf6a63f..6b73bcfb1f 100644
--- a/src/analyzer/protocol/rdp/RDP.cc
+++ b/src/analyzer/protocol/rdp/RDP.cc
@@ -12,7 +12,7 @@ RDP_Analyzer::RDP_Analyzer(Connection* c)
 	interp = new binpac::RDP::RDP_Conn(this);
 
 	had_gap = false;
-	pia = 0;
+	pia = nullptr;
 	}
 
 RDP_Analyzer::~RDP_Analyzer()
@@ -66,8 +66,8 @@ void RDP_Analyzer::DeliverStream(int len, const u_char* data, bool orig)
 					return;
 					}
 
-				pia->FirstPacket(true, 0);
-				pia->FirstPacket(false, 0);
+				pia->FirstPacket(true, nullptr);
+				pia->FirstPacket(false, nullptr);
 				}
 
 			ForwardStream(len, data, orig);
diff --git a/src/analyzer/protocol/rpc/MOUNT.cc b/src/analyzer/protocol/rpc/MOUNT.cc
index f15a9f154a..96fb4df1d2 100644
--- a/src/analyzer/protocol/rpc/MOUNT.cc
+++ b/src/analyzer/protocol/rpc/MOUNT.cc
@@ -22,7 +22,7 @@ bool MOUNT_Interp::RPC_BuildCall(RPC_CallInfo* c, const u_char*& buf, int& n)
 
 	uint32_t proc = c->Proc();
 	// The call arguments, depends on the call type obviously ...
-	Val *callarg = 0;
+	Val *callarg = nullptr;
 
 	switch ( proc ) {
 		case BifEnum::MOUNT3::PROC_NULL:
@@ -41,7 +41,7 @@ bool MOUNT_Interp::RPC_BuildCall(RPC_CallInfo* c, const u_char*& buf, int& n)
 		break;
 
 	default:
-		callarg = 0;
+		callarg = nullptr;
 		if ( proc < BifEnum::MOUNT3::PROC_END_OF_PROCS )
 			{
 			// We know the procedure but haven't implemented it.
@@ -65,7 +65,7 @@ bool MOUNT_Interp::RPC_BuildCall(RPC_CallInfo* c, const u_char*& buf, int& n)
 		// RecordVal was allocated but we failed to fill it). So we
 		// Unref() the call arguments, and we are fine.
 		Unref(callarg);
-		callarg = 0;
+		callarg = nullptr;
 		return false;
 		}
 
@@ -78,8 +78,8 @@ bool MOUNT_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_statu
 			       const u_char*& buf, int& n, double start_time,
 			       double last_time, int reply_len)
 	{
-	EventHandlerPtr event = 0;
-	Val* reply = 0;
+	EventHandlerPtr event = nullptr;
+	Val* reply = nullptr;
 	BifEnum::MOUNT3::status_t mount_status = BifEnum::MOUNT3::MNT3_OK;
 	bool rpc_success = ( rpc_status == BifEnum::RPC_SUCCESS );
 
@@ -104,7 +104,7 @@ bool MOUNT_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_statu
 		// We set the buffer to NULL, the function that extract the
 		// reply from the data stream will then return empty records.
 		//
-		buf = NULL;
+		buf = nullptr;
 		n = 0;
 		}
 
@@ -119,14 +119,14 @@ bool MOUNT_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_statu
 		break;
 
 	case BifEnum::MOUNT3::PROC_UMNT:
-		reply = 0;
+		reply = nullptr;
 		n = 0;
 		mount_status = BifEnum::MOUNT3::MNT3_OK;
 		event = mount_proc_umnt;
 		break;
 
 	case BifEnum::MOUNT3::PROC_UMNT_ALL:
-		reply = 0;
+		reply = nullptr;
 		n = 0;
 		mount_status = BifEnum::MOUNT3::MNT3_OK;
 		event = mount_proc_umnt;
@@ -151,7 +151,7 @@ bool MOUNT_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_statu
 		// There was a parse error. We have to unref the reply. (see
 		// also comments in RPC_BuildCall.
 		Unref(reply);
-		reply = 0;
+		reply = nullptr;
 		return false;
 		}
 
@@ -230,7 +230,7 @@ StringVal* MOUNT_Interp::mount3_fh(const u_char*& buf, int& n)
 	const u_char* fh = extract_XDR_opaque(buf, n, fh_n, 64);
 
 	if ( ! fh )
-		return 0;
+		return nullptr;
 
 	return new StringVal(new BroString(fh, fh_n, false));
 	}
@@ -241,7 +241,7 @@ StringVal* MOUNT_Interp::mount3_filename(const u_char*& buf, int& n)
 	const u_char* name = extract_XDR_opaque(buf, n, name_len);
 
 	if ( ! name )
-		return 0;
+		return nullptr;
 
 	return new StringVal(new BroString(name, name_len, false));
 	}
@@ -288,8 +288,8 @@ RecordVal* MOUNT_Interp::mount3_mnt_reply(const u_char*& buf, int& n,
 		}
 	else
 		{
-		rep->Assign(0, 0);
-		rep->Assign(1, 0);
+		rep->Assign(0, nullptr);
+		rep->Assign(1, nullptr);
 		}
 
 	return rep;
@@ -298,7 +298,7 @@ RecordVal* MOUNT_Interp::mount3_mnt_reply(const u_char*& buf, int& n,
 MOUNT_Analyzer::MOUNT_Analyzer(Connection* conn)
 	: RPC_Analyzer("MOUNT", conn, new MOUNT_Interp(this))
 	{
-	orig_rpc = resp_rpc = 0;
+	orig_rpc = resp_rpc = nullptr;
 	}
 
 void MOUNT_Analyzer::Init()
diff --git a/src/analyzer/protocol/rpc/NFS.cc b/src/analyzer/protocol/rpc/NFS.cc
index bb76727705..b709bee680 100644
--- a/src/analyzer/protocol/rpc/NFS.cc
+++ b/src/analyzer/protocol/rpc/NFS.cc
@@ -22,7 +22,7 @@ bool NFS_Interp::RPC_BuildCall(RPC_CallInfo* c, const u_char*& buf, int& n)
 
 	uint32_t proc = c->Proc();
 	// The call arguments, depends on the call type obviously ...
-	Val *callarg = 0;
+	Val *callarg = nullptr;
 
 	switch ( proc ) {
 	case BifEnum::NFS3::PROC_NULL:
@@ -95,7 +95,7 @@ bool NFS_Interp::RPC_BuildCall(RPC_CallInfo* c, const u_char*& buf, int& n)
 		break;
 
 	default:
-		callarg = 0;
+		callarg = nullptr;
 		if ( proc < BifEnum::NFS3::PROC_END_OF_PROCS )
 			{
 			// We know the procedure but haven't implemented it.
@@ -119,7 +119,7 @@ bool NFS_Interp::RPC_BuildCall(RPC_CallInfo* c, const u_char*& buf, int& n)
 		// RecordVal was allocated but we failed to fill it). So we
 		// Unref() the call arguments, and we are fine.
 		Unref(callarg);
-		callarg = 0;
+		callarg = nullptr;
 		return false;
 		}
 
@@ -132,8 +132,8 @@ bool NFS_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_status,
 			       const u_char*& buf, int& n, double start_time,
 			       double last_time, int reply_len)
 	{
-	EventHandlerPtr event = 0;
-	Val *reply = 0;
+	EventHandlerPtr event = nullptr;
+	Val *reply = nullptr;
 	BifEnum::NFS3::status_t nfs_status = BifEnum::NFS3::NFS3ERR_OK;
 	bool rpc_success = ( rpc_status == BifEnum::RPC_SUCCESS );
 
@@ -158,7 +158,7 @@ bool NFS_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_status,
 		// We set the buffer to NULL, the function that extract the
 		// reply from the data stream will then return empty records.
 		//
-		buf = NULL;
+		buf = nullptr;
 		n = 0;
 		}
 
@@ -263,7 +263,7 @@ bool NFS_Interp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status rpc_status,
 		// There was a parse error. We have to unref the reply. (see
 		// also comments in RPC_BuildCall.
 		Unref(reply);
-		reply = 0;
+		reply = nullptr;
 		return false;
 		}
 
@@ -303,10 +303,10 @@ StringVal* NFS_Interp::nfs3_file_data(const u_char*& buf, int& n, uint64_t offse
 
 	// check whether we have to deliver data to the event
 	if ( ! BifConst::NFS3::return_data )
-		return 0;
+		return nullptr;
 
 	if ( BifConst::NFS3::return_data_first_only && offset != 0 )
-		return 0;
+		return nullptr;
 
 	// Ok, so we want to return some data
 	data_n = min(data_n, size);
@@ -315,7 +315,7 @@ StringVal* NFS_Interp::nfs3_file_data(const u_char*& buf, int& n, uint64_t offse
 	if ( data && data_n > 0 )
 		return new StringVal(new BroString(data, data_n, false));
 
-	return 0;
+	return nullptr;
 	}
 
 zeek::Args NFS_Interp::event_common_vl(RPC_CallInfo *c, BifEnum::rpc_status rpc_status,
@@ -358,7 +358,7 @@ StringVal* NFS_Interp::nfs3_fh(const u_char*& buf, int& n)
 	const u_char* fh = extract_XDR_opaque(buf, n, fh_n, 64);
 
 	if ( ! fh )
-		return 0;
+		return nullptr;
 
 	return new StringVal(new BroString(fh, fh_n, false));
 	}
@@ -368,22 +368,22 @@ RecordVal* NFS_Interp::nfs3_sattr(const u_char*& buf, int& n)
 	{
 	RecordVal* attrs = new RecordVal(BifType::Record::NFS3::sattr_t);
 
-	attrs->Assign(0, 0); // mode
+	attrs->Assign(0, nullptr); // mode
 	int mode_set_it =  extract_XDR_uint32(buf, n);
 	if ( mode_set_it )
 		attrs->Assign(0, ExtractUint32(buf, n)); // mode
 
-	attrs->Assign(1, 0); // uid
+	attrs->Assign(1, nullptr); // uid
 	int uid_set_it =  extract_XDR_uint32(buf, n);
 	if ( uid_set_it )
 		attrs->Assign(1, ExtractUint32(buf, n)); // uid
 
-	attrs->Assign(2, 0); // gid
+	attrs->Assign(2, nullptr); // gid
 	int gid_set_it =  extract_XDR_uint32(buf, n);
 	if ( gid_set_it )
 		attrs->Assign(2, ExtractUint32(buf, n)); // gid
 
-	attrs->Assign(3, 0); // size
+	attrs->Assign(3, nullptr); // size
 	int size_set_it =  extract_XDR_uint32(buf, n);
 	if ( size_set_it )
 		attrs->Assign(3, ExtractTime(buf, n));	 // size
@@ -406,8 +406,8 @@ RecordVal* NFS_Interp::nfs3_sattr_reply(const u_char*& buf, int& n, BifEnum::NFS
 		}
 	else
 		{
-		rep->Assign(1, 0);
-		rep->Assign(2, 0);
+		rep->Assign(1, nullptr);
+		rep->Assign(2, nullptr);
 		}
 
 	return rep;
@@ -464,7 +464,7 @@ StringVal *NFS_Interp::nfs3_filename(const u_char*& buf, int& n)
 	const u_char* name = extract_XDR_opaque(buf, n, name_len);
 
 	if ( ! name )
-		return 0;
+		return nullptr;
 
 	return new StringVal(new BroString(name, name_len, false));
 	}
@@ -508,7 +508,7 @@ RecordVal* NFS_Interp::nfs3_post_op_attr(const u_char*& buf, int& n)
 	if ( have_attrs )
 		return nfs3_fattr(buf, n);
 
-	return 0;
+	return nullptr;
 	}
 
 StringVal* NFS_Interp::nfs3_post_op_fh(const u_char*& buf, int& n)
@@ -518,7 +518,7 @@ StringVal* NFS_Interp::nfs3_post_op_fh(const u_char*& buf, int& n)
 	if ( have_fh )
 		return nfs3_fh(buf, n);
 
-	return 0;
+	return nullptr;
 	}
 
 RecordVal* NFS_Interp::nfs3_pre_op_attr(const u_char*& buf, int& n)
@@ -527,7 +527,7 @@ RecordVal* NFS_Interp::nfs3_pre_op_attr(const u_char*& buf, int& n)
 
 	if ( have_attrs )
 		return nfs3_wcc_attr(buf, n);
-	return 0;
+	return nullptr;
 	}
 
 EnumVal *NFS_Interp::nfs3_stable_how(const u_char*& buf, int& n)
@@ -548,8 +548,8 @@ RecordVal* NFS_Interp::nfs3_lookup_reply(const u_char*& buf, int& n, BifEnum::NF
 		}
 	else
 		{
-		rep->Assign(0, 0);
-		rep->Assign(1, 0);
+		rep->Assign(0, nullptr);
+		rep->Assign(1, nullptr);
 		rep->Assign(2, nfs3_post_op_attr(buf, n));
 		}
 	return rep;
@@ -710,8 +710,8 @@ RecordVal* NFS_Interp::nfs3_newobj_reply(const u_char*& buf, int& n, BifEnum::NF
 		}
 	else
 		{
-		rep->Assign(0, 0);
-		rep->Assign(1, 0);
+		rep->Assign(0, nullptr);
+		rep->Assign(1, nullptr);
 		rep->Assign(2, nfs3_pre_op_attr(buf, n));
 		rep->Assign(3, nfs3_post_op_attr(buf, n));
 		}
@@ -833,7 +833,7 @@ Val* NFS_Interp::ExtractBool(const u_char*& buf, int& n)
 NFS_Analyzer::NFS_Analyzer(Connection* conn)
 	: RPC_Analyzer("NFS", conn, new NFS_Interp(this))
 	{
-	orig_rpc = resp_rpc = 0;
+	orig_rpc = resp_rpc = nullptr;
 	}
 
 void NFS_Analyzer::Init()
diff --git a/src/analyzer/protocol/rpc/Plugin.cc b/src/analyzer/protocol/rpc/Plugin.cc
index da9b5f0299..6e284c9dbf 100644
--- a/src/analyzer/protocol/rpc/Plugin.cc
+++ b/src/analyzer/protocol/rpc/Plugin.cc
@@ -17,8 +17,8 @@ public:
 		AddComponent(new ::analyzer::Component("NFS", ::analyzer::rpc::NFS_Analyzer::Instantiate));
 		AddComponent(new ::analyzer::Component("MOUNT", ::analyzer::rpc::MOUNT_Analyzer::Instantiate));
 		AddComponent(new ::analyzer::Component("Portmapper", ::analyzer::rpc::Portmapper_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("Contents_RPC", 0));
-		AddComponent(new ::analyzer::Component("Contents_NFS", 0));
+		AddComponent(new ::analyzer::Component("Contents_RPC", nullptr));
+		AddComponent(new ::analyzer::Component("Contents_NFS", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::RPC";
diff --git a/src/analyzer/protocol/rpc/Portmap.cc b/src/analyzer/protocol/rpc/Portmap.cc
index c67d1b3c52..ad9fa37f02 100644
--- a/src/analyzer/protocol/rpc/Portmap.cc
+++ b/src/analyzer/protocol/rpc/Portmap.cc
@@ -79,7 +79,7 @@ bool PortmapperInterp::RPC_BuildReply(RPC_CallInfo* c, BifEnum::rpc_status statu
 				     int reply_len)
 	{
 	EventHandlerPtr event;
-	Val *reply = 0;
+	Val *reply = nullptr;
 	int success = (status == BifEnum::RPC_SUCCESS);
 
 	switch ( c->Proc() ) {
@@ -208,7 +208,7 @@ Val* PortmapperInterp::ExtractMapping(const u_char*& buf, int& len)
 	if ( ! buf )
 		{
 		Unref(mapping);
-		return 0;
+		return nullptr;
 		}
 
 	return mapping;
@@ -228,7 +228,7 @@ Val* PortmapperInterp::ExtractPortRequest(const u_char*& buf, int& len)
 	if ( ! buf )
 		{
 		Unref(pr);
-		return 0;
+		return nullptr;
 		}
 
 	return pr;
@@ -249,7 +249,7 @@ Val* PortmapperInterp::ExtractCallItRequest(const u_char*& buf, int& len)
 	if ( ! buf )
 		{
 		Unref(c);
-		return 0;
+		return nullptr;
 		}
 
 	return c;
@@ -307,7 +307,7 @@ void PortmapperInterp::Event(EventHandlerPtr f, Val* request, BifEnum::rpc_statu
 Portmapper_Analyzer::Portmapper_Analyzer(Connection* conn)
 : RPC_Analyzer("PORTMAPPER", conn, new PortmapperInterp(this))
 	{
-	orig_rpc = resp_rpc = 0;
+	orig_rpc = resp_rpc = nullptr;
 	}
 
 Portmapper_Analyzer::~Portmapper_Analyzer()
diff --git a/src/analyzer/protocol/rpc/RPC.h b/src/analyzer/protocol/rpc/RPC.h
index 29685cb77f..a3615bebc5 100644
--- a/src/analyzer/protocol/rpc/RPC.h
+++ b/src/analyzer/protocol/rpc/RPC.h
@@ -54,7 +54,7 @@ public:
 
 	void AddVal(Val* arg_v)		{ Unref(v); v = arg_v; }
 	Val* RequestVal() const		{ return v; }
-	Val* TakeRequestVal()		{ Val* rv = v; v = 0; return rv; }
+	Val* TakeRequestVal()		{ Val* rv = v; v = nullptr; return rv; }
 
 	bool CompareRexmit(const u_char* buf, int n) const;
 
@@ -149,7 +149,7 @@ public:
 	RPC_Reasm_Buffer() {
 		maxsize = expected = 0;
 		fill = processed = 0;
-		buf = 0;
+		buf = nullptr;
 	};
 
 	~RPC_Reasm_Buffer() { if (buf) delete [] buf; }
diff --git a/src/analyzer/protocol/rpc/XDR.cc b/src/analyzer/protocol/rpc/XDR.cc
index 95992d142c..1eddf96a04 100644
--- a/src/analyzer/protocol/rpc/XDR.cc
+++ b/src/analyzer/protocol/rpc/XDR.cc
@@ -17,7 +17,7 @@ uint32_t analyzer::rpc::extract_XDR_uint32(const u_char*& buf, int& len)
 
 	if ( len < 4 )
 		{
-		buf = 0;
+		buf = nullptr;
 		return 0;
 		}
 
@@ -36,7 +36,7 @@ uint64_t analyzer::rpc::extract_XDR_uint64(const u_char*& buf, int& len)
 	{
 	if ( ! buf || len < 8 )
 		{
-		buf = 0;
+		buf = nullptr;
 		return 0;
 		}
 
@@ -50,7 +50,7 @@ double analyzer::rpc::extract_XDR_time(const u_char*& buf, int& len)
 	{
 	if ( ! buf || len < 8 )
 		{
-		buf = 0;
+		buf = nullptr;
 		return 0.0;
 		}
 
@@ -64,15 +64,15 @@ const u_char* analyzer::rpc::extract_XDR_opaque(const u_char*& buf, int& len, in
 	{
 	n = int(extract_XDR_uint32(buf, len));
 	if ( ! buf )
-		return 0;
+		return nullptr;
 
 	if ( short_buf_ok )
 		n = std::min(n, len);
 
 	if ( n < 0 || n > len || n > max_len )
 		{ // ### Should really flag this as a different sort of error.
-		buf = 0;
-		return 0;
+		buf = nullptr;
+		return nullptr;
 		}
 
 	int n4 = ((n + 3) >> 2) << 2;	// n rounded up to next multiple of 4
@@ -87,11 +87,11 @@ const u_char* analyzer::rpc::extract_XDR_opaque(const u_char*& buf, int& len, in
 const u_char* analyzer::rpc::extract_XDR_opaque_fixed(const u_char*& buf, int& len, int n)
 	{
 	if ( ! buf )
-		return 0;
+		return nullptr;
 	if ( n < 0 || n > len)
 		{
-		buf = 0;
-		return 0;
+		buf = nullptr;
+		return nullptr;
 		}
 	int n4 = ((n + 3) >> 2) << 2;	// n rounded up to next multiple of 4
 
diff --git a/src/analyzer/protocol/smb/Plugin.cc b/src/analyzer/protocol/smb/Plugin.cc
index aaf84af9f5..2c10066eed 100644
--- a/src/analyzer/protocol/smb/Plugin.cc
+++ b/src/analyzer/protocol/smb/Plugin.cc
@@ -12,7 +12,7 @@ public:
 	plugin::Configuration Configure() override
 		{
 		AddComponent(new ::analyzer::Component("SMB", ::analyzer::smb::SMB_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("Contents_SMB", 0));
+		AddComponent(new ::analyzer::Component("Contents_SMB", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::SMB";
diff --git a/src/analyzer/protocol/smtp/SMTP.cc b/src/analyzer/protocol/smtp/SMTP.cc
index eee9ac81b8..0494bee0c0 100644
--- a/src/analyzer/protocol/smtp/SMTP.cc
+++ b/src/analyzer/protocol/smtp/SMTP.cc
@@ -43,8 +43,8 @@ SMTP_Analyzer::SMTP_Analyzer(Connection* conn)
 
 	skip_data = false;
 	orig_is_sender = true;
-	line_after_gap = 0;
-	mail = 0;
+	line_after_gap = nullptr;
+	mail = nullptr;
 	UpdateState(first_cmd, 0, true);
 	cl_orig = new tcp::ContentLine_Analyzer(conn, true);
 	cl_orig->SetIsNULSensitive(true);
@@ -103,7 +103,7 @@ void SMTP_Analyzer::Undelivered(uint64_t seq, int len, bool is_orig)
 	if ( line_after_gap )
 		{
 		delete line_after_gap;
-		line_after_gap = 0;
+		line_after_gap = nullptr;
 		}
 
 	pending_cmd_q.clear();
@@ -247,7 +247,7 @@ void SMTP_Analyzer::ProcessLine(int length, const char* line, bool orig)
 			if ( cmd_code == -1 )
 				{
 				Unexpected(true, "unknown command", cmd_len, cmd);
-				cmd = 0;
+				cmd = nullptr;
 				}
 			else
 				NewCmd(cmd_code);
@@ -921,7 +921,7 @@ void SMTP_Analyzer::BeginData(bool orig)
 	{
 	state = SMTP_IN_DATA;
 	skip_data = false; // reset the flag at the beginning of the mail
-	if ( mail != 0 )
+	if ( mail != nullptr )
 		{
 		Weird("smtp_nested_mail_transaction");
 		mail->Done();
@@ -939,6 +939,6 @@ void SMTP_Analyzer::EndData()
 		{
 		mail->Done();
 		delete mail;
-		mail = 0;
+		mail = nullptr;
 		}
 	}
diff --git a/src/analyzer/protocol/socks/SOCKS.cc b/src/analyzer/protocol/socks/SOCKS.cc
index 83663f41b6..6490f38165 100644
--- a/src/analyzer/protocol/socks/SOCKS.cc
+++ b/src/analyzer/protocol/socks/SOCKS.cc
@@ -11,7 +11,7 @@ SOCKS_Analyzer::SOCKS_Analyzer(Connection* conn)
 	{
 	interp = new binpac::SOCKS::SOCKS_Conn(this);
 	orig_done = resp_done = false;
-	pia = 0;
+	pia = nullptr;
 	}
 
 SOCKS_Analyzer::~SOCKS_Analyzer()
@@ -63,11 +63,11 @@ void SOCKS_Analyzer::DeliverStream(int len, const u_char* data, bool orig)
 			pia = new pia::PIA_TCP(Conn());
 			if ( AddChildAnalyzer(pia) )
 				{
-				pia->FirstPacket(true, 0);
-				pia->FirstPacket(false, 0);
+				pia->FirstPacket(true, nullptr);
+				pia->FirstPacket(false, nullptr);
 				}
 			else
-				pia = 0;
+				pia = nullptr;
 			}
 
 		ForwardStream(len, data, orig);
diff --git a/src/analyzer/protocol/stepping-stone/SteppingStone.cc b/src/analyzer/protocol/stepping-stone/SteppingStone.cc
index 54351768f4..42332a59c5 100644
--- a/src/analyzer/protocol/stepping-stone/SteppingStone.cc
+++ b/src/analyzer/protocol/stepping-stone/SteppingStone.cc
@@ -158,7 +158,7 @@ SteppingStone_Analyzer::SteppingStone_Analyzer(Connection* c)
 	{
 	stp_manager = sessions->GetSTPManager();
 
-	orig_endp = resp_endp = 0;
+	orig_endp = resp_endp = nullptr;
 	orig_stream_pos = resp_stream_pos = 1;
 	}
 
@@ -179,9 +179,9 @@ void SteppingStone_Analyzer::DeliverPacket(int len, const u_char* data,
 						ip, caplen);
 
 	if ( is_orig )
-		orig_endp->DataSent(network_time, seq, len, caplen, data, 0, 0);
+		orig_endp->DataSent(network_time, seq, len, caplen, data, nullptr, nullptr);
 	else
-		resp_endp->DataSent(network_time, seq, len, caplen, data, 0, 0);
+		resp_endp->DataSent(network_time, seq, len, caplen, data, nullptr, nullptr);
 	}
 
 void SteppingStone_Analyzer::DeliverStream(int len, const u_char* data,
@@ -192,14 +192,14 @@ void SteppingStone_Analyzer::DeliverStream(int len, const u_char* data,
 	if ( is_orig )
 		{
 		orig_endp->DataSent(network_time, orig_stream_pos, len, len,
-					data, 0, 0);
+					data, nullptr, nullptr);
 		orig_stream_pos += len;
 		}
 
 	else
 		{
 		resp_endp->DataSent(network_time, resp_stream_pos, len, len,
-					data, 0, 0);
+					data, nullptr, nullptr);
 		resp_stream_pos += len;
 		}
 	}
diff --git a/src/analyzer/protocol/tcp/ContentLine.cc b/src/analyzer/protocol/tcp/ContentLine.cc
index 193a18fa65..5e0dfd81b2 100644
--- a/src/analyzer/protocol/tcp/ContentLine.cc
+++ b/src/analyzer/protocol/tcp/ContentLine.cc
@@ -24,7 +24,7 @@ void ContentLine_Analyzer::InitState()
 	CR_LF_as_EOL = (CR_as_EOL | LF_as_EOL);
 	skip_deliveries = false;
 	skip_partial = false;
-	buf = 0;
+	buf = nullptr;
 	seq_delivered_in_lines = 0;
 	skip_pending = 0;
 	seq = 0;
diff --git a/src/analyzer/protocol/tcp/Plugin.cc b/src/analyzer/protocol/tcp/Plugin.cc
index d96c3ca3ed..9f06936baa 100644
--- a/src/analyzer/protocol/tcp/Plugin.cc
+++ b/src/analyzer/protocol/tcp/Plugin.cc
@@ -13,8 +13,8 @@ public:
 		{
 		AddComponent(new ::analyzer::Component("TCP", ::analyzer::tcp::TCP_Analyzer::Instantiate));
 		AddComponent(new ::analyzer::Component("TCPStats", ::analyzer::tcp::TCPStats_Analyzer::Instantiate));
-		AddComponent(new ::analyzer::Component("CONTENTLINE", 0));
-		AddComponent(new ::analyzer::Component("Contents", 0));
+		AddComponent(new ::analyzer::Component("CONTENTLINE", nullptr));
+		AddComponent(new ::analyzer::Component("Contents", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::TCP";
diff --git a/src/analyzer/protocol/tcp/TCP.cc b/src/analyzer/protocol/tcp/TCP.cc
index 6d6ad3a41b..8a8f300397 100644
--- a/src/analyzer/protocol/tcp/TCP.cc
+++ b/src/analyzer/protocol/tcp/TCP.cc
@@ -192,7 +192,7 @@ analyzer::Analyzer* TCP_Analyzer::FindChild(ID arg_id)
 			return child;
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 analyzer::Analyzer* TCP_Analyzer::FindChild(Tag arg_tag)
@@ -209,7 +209,7 @@ analyzer::Analyzer* TCP_Analyzer::FindChild(Tag arg_tag)
 			return child;
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 bool TCP_Analyzer::RemoveChildAnalyzer(ID id)
@@ -253,7 +253,7 @@ const struct tcphdr* TCP_Analyzer::ExtractTCP_Header(const u_char*& data,
 	if ( tcp_hdr_len < sizeof(struct tcphdr) )
 		{
 		Weird("bad_TCP_header_len");
-		return 0;
+		return nullptr;
 		}
 
 	if ( tcp_hdr_len > uint32_t(len) ||
@@ -262,7 +262,7 @@ const struct tcphdr* TCP_Analyzer::ExtractTCP_Header(const u_char*& data,
 		// This can happen even with the above test, due to TCP
 		// options.
 		Weird("truncated_header");
-		return 0;
+		return nullptr;
 		}
 
 	len -= tcp_hdr_len;	// remove TCP header
@@ -1587,8 +1587,8 @@ void TCP_Analyzer::SetContentsFile(unsigned int direction, BroFile* f)
 	{
 	if ( direction == CONTENTS_NONE )
 		{
-		orig->SetContentsFile(0);
-		resp->SetContentsFile(0);
+		orig->SetContentsFile(nullptr);
+		resp->SetContentsFile(nullptr);
 		}
 
 	else
@@ -1604,7 +1604,7 @@ BroFile* TCP_Analyzer::GetContentsFile(unsigned int direction) const
 	{
 	switch ( direction ) {
 	case CONTENTS_NONE:
-		return 0;
+		return nullptr;
 
 	case CONTENTS_ORIG:
 		return orig->GetContentsFile();
@@ -1615,7 +1615,7 @@ BroFile* TCP_Analyzer::GetContentsFile(unsigned int direction) const
 	case CONTENTS_BOTH:
 		if ( orig->GetContentsFile() != resp->GetContentsFile())
 			// This is an "error".
-			return 0;
+			return nullptr;
 		else
 			return orig->GetContentsFile();
 
@@ -1625,7 +1625,7 @@ BroFile* TCP_Analyzer::GetContentsFile(unsigned int direction) const
 
 	reporter->Error("bad direction %u in TCP_Analyzer::GetContentsFile",
 	                direction);
-	return 0;
+	return nullptr;
 	}
 
 void TCP_Analyzer::ConnectionClosed(TCP_Endpoint* endpoint, TCP_Endpoint* peer,
@@ -2127,7 +2127,7 @@ void TCPStats_Analyzer::DeliverPacket(int len, const u_char* data, bool is_orig,
 	TCP_ApplicationAnalyzer::DeliverPacket(len, data, is_orig, seq, ip, caplen);
 
 	if ( is_orig )
-		orig_stats->DataSent(network_time, seq, len, caplen, data, ip, 0);
+		orig_stats->DataSent(network_time, seq, len, caplen, data, ip, nullptr);
 	else
-		resp_stats->DataSent(network_time, seq, len, caplen, data, ip, 0);
+		resp_stats->DataSent(network_time, seq, len, caplen, data, ip, nullptr);
 	}
diff --git a/src/analyzer/protocol/tcp/TCP.h b/src/analyzer/protocol/tcp/TCP.h
index e9d69f00c8..a5e67330d2 100644
--- a/src/analyzer/protocol/tcp/TCP.h
+++ b/src/analyzer/protocol/tcp/TCP.h
@@ -161,7 +161,7 @@ protected:
 	// A couple utility functions that may also be useful to derived analyzers.
 	static uint64_t get_relative_seq(const TCP_Endpoint* endpoint,
 	                               uint32_t cur_base, uint32_t last,
-	                               uint32_t wraps, bool* underflow = 0);
+	                               uint32_t wraps, bool* underflow = nullptr);
 
 	static int get_segment_len(int payload_len, TCP_Flags flags);
 
@@ -192,12 +192,10 @@ private:
 class TCP_ApplicationAnalyzer : public analyzer::Analyzer {
 public:
 	TCP_ApplicationAnalyzer(const char* name, Connection* conn)
-	: Analyzer(name, conn)
-		{ tcp = 0; }
+		: Analyzer(name, conn), tcp(nullptr) { }
 
 	explicit TCP_ApplicationAnalyzer(Connection* conn)
-	: Analyzer(conn)
-		{ tcp = 0; }
+		: Analyzer(conn), tcp(nullptr) { }
 
 	~TCP_ApplicationAnalyzer() override { }
 
@@ -235,7 +233,7 @@ public:
 	// This suppresses violations if the TCP connection wasn't
 	// fully established.
 	void ProtocolViolation(const char* reason,
-					const char* data = 0, int len = 0) override;
+					const char* data = nullptr, int len = 0) override;
 
 	// "name" and "val" both now belong to this object, which needs to
 	//  delete them when done with them.
diff --git a/src/analyzer/protocol/tcp/TCP_Endpoint.cc b/src/analyzer/protocol/tcp/TCP_Endpoint.cc
index 59f0b21778..f0fb129d6d 100644
--- a/src/analyzer/protocol/tcp/TCP_Endpoint.cc
+++ b/src/analyzer/protocol/tcp/TCP_Endpoint.cc
@@ -16,9 +16,9 @@ using namespace analyzer::tcp;
 
 TCP_Endpoint::TCP_Endpoint(TCP_Analyzer* arg_analyzer, bool arg_is_orig)
 	{
-	contents_processor = 0;
+	contents_processor = nullptr;
 	prev_state = state = TCP_ENDPOINT_INACTIVE;
-	peer = 0;
+	peer = nullptr;
 	start_time = last_time = 0.0;
 	start_seq = last_seq = ack_seq = 0;
 	seq_wraps = ack_wraps = 0;
@@ -29,7 +29,7 @@ TCP_Endpoint::TCP_Endpoint(TCP_Analyzer* arg_analyzer, bool arg_is_orig)
 	FIN_seq = 0;
 	SYN_cnt = FIN_cnt = RST_cnt = 0;
 	did_close = false;
-	contents_file = 0;
+	contents_file = nullptr;
 	tcp_analyzer = arg_analyzer;
 	is_orig = arg_is_orig;
 
diff --git a/src/analyzer/protocol/tcp/TCP_Endpoint.h b/src/analyzer/protocol/tcp/TCP_Endpoint.h
index 79c9ee2849..e72016e4a2 100644
--- a/src/analyzer/protocol/tcp/TCP_Endpoint.h
+++ b/src/analyzer/protocol/tcp/TCP_Endpoint.h
@@ -141,7 +141,7 @@ public:
 
 	Connection* Conn() const;
 
-	bool HasContents() const		{ return contents_processor != 0; }
+	bool HasContents() const		{ return contents_processor != nullptr; }
 	bool HadGap() const;
 
 	inline bool IsOrig() const		{ return is_orig; }
diff --git a/src/analyzer/protocol/tcp/TCP_Reassembler.cc b/src/analyzer/protocol/tcp/TCP_Reassembler.cc
index f77cbda026..697e8d7325 100644
--- a/src/analyzer/protocol/tcp/TCP_Reassembler.cc
+++ b/src/analyzer/protocol/tcp/TCP_Reassembler.cc
@@ -30,7 +30,7 @@ TCP_Reassembler::TCP_Reassembler(analyzer::Analyzer* arg_dst_analyzer,
 	type = arg_type;
 	endp = arg_endp;
 	had_gap = false;
-	record_contents_file = 0;
+	record_contents_file = nullptr;
 	deliver_tcp_contents = false;
 	skip_deliveries = false;
 	did_EOF = false;
diff --git a/src/analyzer/protocol/tcp/functions.bif b/src/analyzer/protocol/tcp/functions.bif
index 5c6448eec1..7b0e2b6876 100644
--- a/src/analyzer/protocol/tcp/functions.bif
+++ b/src/analyzer/protocol/tcp/functions.bif
@@ -121,7 +121,7 @@ function set_contents_file%(cid: conn_id, direction: count, f: file%): bool
 function get_contents_file%(cid: conn_id, direction: count%): file
 	%{
 	Connection* c = sessions->FindConnection(cid);
-	BroFile* f = c ? c->GetRootAnalyzer()->GetContentsFile(direction) : 0;
+	BroFile* f = c ? c->GetRootAnalyzer()->GetContentsFile(direction) : nullptr;
 
 	if ( f )
 		{
diff --git a/src/analyzer/protocol/teredo/Teredo.cc b/src/analyzer/protocol/teredo/Teredo.cc
index 2089fd3f3e..3b1667be29 100644
--- a/src/analyzer/protocol/teredo/Teredo.cc
+++ b/src/analyzer/protocol/teredo/Teredo.cc
@@ -98,9 +98,9 @@ bool TeredoEncapsulation::DoParse(const u_char* data, int& len,
 
 RecordVal* TeredoEncapsulation::BuildVal(const IP_Hdr* inner) const
 	{
-	static RecordType* teredo_hdr_type = 0;
-	static RecordType* teredo_auth_type = 0;
-	static RecordType* teredo_origin_type = 0;
+	static RecordType* teredo_hdr_type = nullptr;
+	static RecordType* teredo_auth_type = nullptr;
+	static RecordType* teredo_origin_type = nullptr;
 
 	if ( ! teredo_hdr_type )
 		{
@@ -167,7 +167,7 @@ void Teredo_Analyzer::DeliverPacket(int len, const u_char* data, bool orig,
 		return;
 		}
 
-	IP_Hdr* inner = 0;
+	IP_Hdr* inner = nullptr;
 	int rslt = sessions->ParseIPPacket(len, te.InnerIP(), IPPROTO_IPV6, inner);
 
 	if ( rslt > 0 )
@@ -201,33 +201,33 @@ void Teredo_Analyzer::DeliverPacket(int len, const u_char* data, bool orig,
 		return;
 		}
 
-	Val* teredo_hdr = 0;
+	Val* teredo_hdr = nullptr;
 
 	if ( teredo_packet )
 		{
 		teredo_hdr = te.BuildVal(inner);
-		Conn()->Event(teredo_packet, 0, teredo_hdr);
+		Conn()->Event(teredo_packet, nullptr, teredo_hdr);
 		}
 
 	if ( te.Authentication() && teredo_authentication )
 		{
 		teredo_hdr = teredo_hdr ? teredo_hdr->Ref() : te.BuildVal(inner);
-		Conn()->Event(teredo_authentication, 0, teredo_hdr);
+		Conn()->Event(teredo_authentication, nullptr, teredo_hdr);
 		}
 
 	if ( te.OriginIndication() && teredo_origin_indication )
 		{
 		teredo_hdr = teredo_hdr ? teredo_hdr->Ref() : te.BuildVal(inner);
-		Conn()->Event(teredo_origin_indication, 0, teredo_hdr);
+		Conn()->Event(teredo_origin_indication, nullptr, teredo_hdr);
 		}
 
 	if ( inner->NextProto() == IPPROTO_NONE && teredo_bubble )
 		{
 		teredo_hdr = teredo_hdr ? teredo_hdr->Ref() : te.BuildVal(inner);
-		Conn()->Event(teredo_bubble, 0, teredo_hdr);
+		Conn()->Event(teredo_bubble, nullptr, teredo_hdr);
 		}
 
 	EncapsulatingConn ec(Conn(), BifEnum::Tunnel::TEREDO);
 
-	sessions->DoNextInnerPacket(network_time, 0, inner, e, ec);
+	sessions->DoNextInnerPacket(network_time, nullptr, inner, e, ec);
 	}
diff --git a/src/analyzer/protocol/teredo/Teredo.h b/src/analyzer/protocol/teredo/Teredo.h
index 1fe9b76b57..55d01b66a2 100644
--- a/src/analyzer/protocol/teredo/Teredo.h
+++ b/src/analyzer/protocol/teredo/Teredo.h
@@ -55,7 +55,7 @@ protected:
 class TeredoEncapsulation {
 public:
 	explicit TeredoEncapsulation(const Teredo_Analyzer* ta)
-		: inner_ip(0), origin_indication(0), auth(0), analyzer(ta)
+		: inner_ip(nullptr), origin_indication(nullptr), auth(nullptr), analyzer(ta)
 		{}
 
 	/**
diff --git a/src/analyzer/protocol/vxlan/VXLAN.cc b/src/analyzer/protocol/vxlan/VXLAN.cc
index b7ed5322f7..ff41444295 100644
--- a/src/analyzer/protocol/vxlan/VXLAN.cc
+++ b/src/analyzer/protocol/vxlan/VXLAN.cc
@@ -101,7 +101,7 @@ void VXLAN_Analyzer::DeliverPacket(int len, const u_char* data, bool orig,
 	ProtocolConfirmation();
 
 	if ( vxlan_packet )
-		Conn()->Event(vxlan_packet, 0, inner->BuildPktHdrVal(),
+		Conn()->Event(vxlan_packet, nullptr, inner->BuildPktHdrVal(),
 		              val_mgr->GetCount(vni));
 
 	EncapsulatingConn ec(Conn(), BifEnum::Tunnel::VXLAN);
diff --git a/src/analyzer/protocol/zip/Plugin.cc b/src/analyzer/protocol/zip/Plugin.cc
index e80d4c6a8c..d59cde2ca0 100644
--- a/src/analyzer/protocol/zip/Plugin.cc
+++ b/src/analyzer/protocol/zip/Plugin.cc
@@ -11,7 +11,7 @@ class Plugin : public plugin::Plugin {
 public:
 	plugin::Configuration Configure() override
 		{
-		AddComponent(new ::analyzer::Component("ZIP", 0));
+		AddComponent(new ::analyzer::Component("ZIP", nullptr));
 
 		plugin::Configuration config;
 		config.name = "Zeek::ZIP";
diff --git a/src/analyzer/protocol/zip/ZIP.cc b/src/analyzer/protocol/zip/ZIP.cc
index d44c6353cd..4b94912e75 100644
--- a/src/analyzer/protocol/zip/ZIP.cc
+++ b/src/analyzer/protocol/zip/ZIP.cc
@@ -7,7 +7,7 @@ using namespace analyzer::zip;
 ZIP_Analyzer::ZIP_Analyzer(Connection* conn, bool orig, Method arg_method)
 : tcp::TCP_SupportAnalyzer("ZIP", conn, orig)
 	{
-	zip = 0;
+	zip = nullptr;
 	zip_status = Z_OK;
 	method = arg_method;
 
@@ -26,7 +26,7 @@ ZIP_Analyzer::ZIP_Analyzer(Connection* conn, bool orig, Method arg_method)
 		{
 		Weird("inflate_init_failed");
 		delete zip;
-		zip = 0;
+		zip = nullptr;
 		}
 	}
 
diff --git a/src/broker/Manager.cc b/src/broker/Manager.cc
index 79864ae86c..8c72ca7cc6 100644
--- a/src/broker/Manager.cc
+++ b/src/broker/Manager.cc
@@ -695,7 +695,7 @@ RecordVal* Manager::MakeEvent(val_list* args, Frame* frame)
 	auto rval = new RecordVal(BifType::Record::Broker::Event);
 	auto arg_vec = new VectorVal(vector_of_data_type);
 	rval->Assign(1, arg_vec);
-	Func* func = 0;
+	Func* func = nullptr;
 	scoped_reporter_location srl{frame};
 
 	for ( auto i = 0; i < args->length(); ++i )
@@ -738,7 +738,7 @@ RecordVal* Manager::MakeEvent(val_list* args, Frame* frame)
 
 		if ( ! same_type(got_type, expected_type) )
 			{
-			rval->Assign(0, 0);
+			rval->Assign(0, nullptr);
 			Error("event parameter #%d type mismatch, got %s, expect %s", i,
 			      type_name(got_type->Tag()),
 			      type_name(expected_type->Tag()));
@@ -758,7 +758,7 @@ RecordVal* Manager::MakeEvent(val_list* args, Frame* frame)
 		if ( ! data_val->Lookup(0) )
 			{
 			Unref(data_val);
-			rval->Assign(0, 0);
+			rval->Assign(0, nullptr);
 			Error("failed to convert param #%d of type %s to broker data",
 				  i, type_name(got_type->Tag()));
 			return rval;
diff --git a/src/file_analysis/AnalyzerSet.cc b/src/file_analysis/AnalyzerSet.cc
index 2c4dc50189..3ea6f5f925 100644
--- a/src/file_analysis/AnalyzerSet.cc
+++ b/src/file_analysis/AnalyzerSet.cc
@@ -83,7 +83,7 @@ Analyzer* AnalyzerSet::QueueAdd(const file_analysis::Tag& tag, RecordVal* args)
 	if ( ! a )
 		{
 		delete key;
-		return 0;
+		return nullptr;
 		}
 
 	mod_queue.push(new AddMod(a, key));
@@ -184,7 +184,7 @@ file_analysis::Analyzer* AnalyzerSet::InstantiateAnalyzer(const Tag& tag,
 		reporter->Error("[%s] Failed file analyzer %s instantiation",
 		                file->GetID().c_str(),
 		                file_mgr->GetComponentName(tag).c_str());
-		return 0;
+		return nullptr;
 		}
 
 	return a;
diff --git a/src/file_analysis/File.cc b/src/file_analysis/File.cc
index 045c5c8026..b526fdd80c 100644
--- a/src/file_analysis/File.cc
+++ b/src/file_analysis/File.cc
@@ -82,7 +82,7 @@ void File::StaticInit()
 
 File::File(const string& file_id, const string& source_name, Connection* conn,
            analyzer::Tag tag, bool is_orig)
-	: id(file_id), val(0), file_reassembler(0), stream_offset(0),
+	: id(file_id), val(nullptr), file_reassembler(nullptr), stream_offset(0),
 	  reassembly_max_buffer(0), did_metadata_inference(false),
 	  reassembly_enabled(false), postpone_timeout(false), done(false),
 	  analyzers(this)
@@ -260,7 +260,7 @@ bool File::AddAnalyzer(file_analysis::Tag tag, RecordVal* args)
 	if ( done )
 		return false;
 
-	return analyzers.QueueAdd(tag, args) != 0;
+	return analyzers.QueueAdd(tag, args) != nullptr;
 	}
 
 bool File::RemoveAnalyzer(file_analysis::Tag tag, RecordVal* args)
@@ -280,7 +280,7 @@ void File::DisableReassembly()
 	{
 	reassembly_enabled = false;
 	delete file_reassembler;
-	file_reassembler = 0;
+	file_reassembler = nullptr;
 	}
 
 void File::SetReassemblyBuffer(uint64_t max)
@@ -386,7 +386,7 @@ void File::DeliverStream(const u_char* data, uint64_t len)
 	        fmt_bytes((const char*) data, min((uint64_t)40, len)),
 	        len > 40 ? "..." : "");
 
-	file_analysis::Analyzer* a = 0;
+	file_analysis::Analyzer* a = nullptr;
 	IterCookie* c = analyzers.InitForIteration();
 
 	while ( (a = analyzers.NextEntry(c)) )
@@ -490,7 +490,7 @@ void File::DeliverChunk(const u_char* data, uint64_t len, uint64_t offset)
 	        fmt_bytes((const char*) data, min((uint64_t)40, len)),
 	        len > 40 ? "..." : "");
 
-	file_analysis::Analyzer* a = 0;
+	file_analysis::Analyzer* a = nullptr;
 	IterCookie* c = analyzers.InitForIteration();
 
 	while ( (a = analyzers.NextEntry(c)) )
@@ -554,7 +554,7 @@ void File::EndOfFile()
 
 	done = true;
 
-	file_analysis::Analyzer* a = 0;
+	file_analysis::Analyzer* a = nullptr;
 	IterCookie* c = analyzers.InitForIteration();
 
 	while ( (a = analyzers.NextEntry(c)) )
@@ -587,7 +587,7 @@ void File::Gap(uint64_t offset, uint64_t len)
 		DeliverStream((const u_char*) "", 0);
 		}
 
-	file_analysis::Analyzer* a = 0;
+	file_analysis::Analyzer* a = nullptr;
 	IterCookie* c = analyzers.InitForIteration();
 
 	while ( (a = analyzers.NextEntry(c)) )
diff --git a/src/file_analysis/File.h b/src/file_analysis/File.h
index 3b0f06e6f4..ee9c447278 100644
--- a/src/file_analysis/File.h
+++ b/src/file_analysis/File.h
@@ -236,7 +236,7 @@ protected:
 	 *        of the connection to the responder.  False indicates the other
 	 *        direction.
 	 */
-	File(const string& file_id, const string& source_name, Connection* conn = 0,
+	File(const string& file_id, const string& source_name, Connection* conn = nullptr,
 	     analyzer::Tag tag = analyzer::Tag::Error, bool is_orig = false);
 
 	/**
diff --git a/src/file_analysis/FileReassembler.cc b/src/file_analysis/FileReassembler.cc
index ffc2fda54f..d42acb5301 100644
--- a/src/file_analysis/FileReassembler.cc
+++ b/src/file_analysis/FileReassembler.cc
@@ -13,7 +13,7 @@ FileReassembler::FileReassembler(File *f, uint64_t starting_offset)
 	}
 
 FileReassembler::FileReassembler()
-	: Reassembler(), the_file(0), flushing(false)
+	: Reassembler(), the_file(nullptr), flushing(false)
 	{
 	}
 
diff --git a/src/file_analysis/Manager.cc b/src/file_analysis/Manager.cc
index 72a1a5b079..9383041394 100644
--- a/src/file_analysis/Manager.cc
+++ b/src/file_analysis/Manager.cc
@@ -16,8 +16,8 @@
 
 using namespace file_analysis;
 
-TableVal* Manager::disabled = 0;
-TableType* Manager::tag_set_type = 0;
+TableVal* Manager::disabled = nullptr;
+TableType* Manager::tag_set_type = nullptr;
 string Manager::salt;
 
 Manager::Manager()
@@ -159,7 +159,7 @@ string Manager::DataIn(const u_char* data, uint64_t len, const analyzer::Tag& ta
 void Manager::DataIn(const u_char* data, uint64_t len, const string& file_id,
                      const string& source)
 	{
-	File* file = GetFile(file_id, 0, analyzer::Tag::Error, false, false,
+	File* file = GetFile(file_id, nullptr, analyzer::Tag::Error, false, false,
 	                     source.c_str());
 
 	if ( ! file )
@@ -306,10 +306,10 @@ File* Manager::GetFile(const string& file_id, Connection* conn,
                        const char* source_name)
 	{
 	if ( file_id.empty() )
-		return 0;
+		return nullptr;
 
 	if ( IsIgnored(file_id) )
-		return 0;
+		return nullptr;
 
 	File* rval = LookupFile(file_id);
 
@@ -334,7 +334,7 @@ File* Manager::GetFile(const string& file_id, Connection* conn,
 		rval->RaiseFileOverNewConnection(conn, is_orig);
 
 		if ( IsIgnored(file_id) )
-			return 0;
+			return nullptr;
 		}
 	else
 		{
@@ -466,14 +466,14 @@ Analyzer* Manager::InstantiateAnalyzer(const Tag& tag, RecordVal* args, File* f)
 		reporter->InternalWarning(
 		            "unknown file analyzer instantiation request: %s",
 		            tag.AsString().c_str());
-		return 0;
+		return nullptr;
 		}
 
 	if ( ! c->Factory() )
 		{
 		reporter->InternalWarning("file analyzer %s cannot be instantiated "
 					  "dynamically", c->CanonicalName().c_str());
-		return 0;
+		return nullptr;
 		}
 
 	DBG_LOG(DBG_FILE_ANALYSIS, "[%s] Instantiate analyzer %s",
diff --git a/src/file_analysis/Manager.h b/src/file_analysis/Manager.h
index 02da6aa182..6eb23acf73 100644
--- a/src/file_analysis/Manager.h
+++ b/src/file_analysis/Manager.h
@@ -358,10 +358,10 @@ protected:
 	 *         exist, the activity time is refreshed along with any
 	 *         connection-related fields.
 	 */
-	File* GetFile(const string& file_id, Connection* conn = 0,
+	File* GetFile(const string& file_id, Connection* conn = nullptr,
 	              const analyzer::Tag& tag = analyzer::Tag::Error,
 	              bool is_orig = false, bool update_conn = true,
-	              const char* source_name = 0);
+	              const char* source_name = nullptr);
 
 	/**
 	 * Evaluate timeout policy for a file and remove the File object mapped to
diff --git a/src/file_analysis/analyzer/data_event/DataEvent.cc b/src/file_analysis/analyzer/data_event/DataEvent.cc
index 4277ee1dda..7c669288fb 100644
--- a/src/file_analysis/analyzer/data_event/DataEvent.cc
+++ b/src/file_analysis/analyzer/data_event/DataEvent.cc
@@ -24,7 +24,7 @@ file_analysis::Analyzer* DataEvent::Instantiate(RecordVal* args, File* file)
 	auto chunk_val = args->Lookup("chunk_event");
 	auto stream_val = args->Lookup("stream_event");
 
-	if ( ! chunk_val && ! stream_val ) return 0;
+	if ( ! chunk_val && ! stream_val ) return nullptr;
 
 	EventHandlerPtr chunk;
 	EventHandlerPtr stream;
diff --git a/src/file_analysis/analyzer/extract/Extract.cc b/src/file_analysis/analyzer/extract/Extract.cc
index 2a4a5a54f7..203b201635 100644
--- a/src/file_analysis/analyzer/extract/Extract.cc
+++ b/src/file_analysis/analyzer/extract/Extract.cc
@@ -48,7 +48,7 @@ file_analysis::Analyzer* Extract::Instantiate(RecordVal* args, File* file)
 	auto limit = get_extract_field_val(args, "extract_limit");
 
 	if ( ! fname || ! limit )
-		return 0;
+		return nullptr;
 
 	return new Extract(args, file, fname->AsString()->CheckString(),
 	                   limit->AsCount());
diff --git a/src/file_analysis/analyzer/hash/Hash.h b/src/file_analysis/analyzer/hash/Hash.h
index f9ca8f8c63..903fc7d6f7 100644
--- a/src/file_analysis/analyzer/hash/Hash.h
+++ b/src/file_analysis/analyzer/hash/Hash.h
@@ -84,7 +84,7 @@ public:
 	 *         handler for the "file_hash" event.
 	 */
 	static file_analysis::Analyzer* Instantiate(RecordVal* args, File* file)
-		{ return file_hash ? new MD5(args, file) : 0; }
+		{ return file_hash ? new MD5(args, file) : nullptr; }
 
 protected:
 
@@ -112,7 +112,7 @@ public:
 	 *         handler for the "file_hash" event.
 	 */
 	static file_analysis::Analyzer* Instantiate(RecordVal* args, File* file)
-		{ return file_hash ? new SHA1(args, file) : 0; }
+		{ return file_hash ? new SHA1(args, file) : nullptr; }
 
 protected:
 
@@ -140,7 +140,7 @@ public:
 	 *         handler for the "file_hash" event.
 	 */
 	static file_analysis::Analyzer* Instantiate(RecordVal* args, File* file)
-		{ return file_hash ? new SHA256(args, file) : 0; }
+		{ return file_hash ? new SHA256(args, file) : nullptr; }
 
 protected:
 
diff --git a/src/file_analysis/analyzer/x509/X509.cc b/src/file_analysis/analyzer/x509/X509.cc
index 6085bbdf6a..b990d0511c 100644
--- a/src/file_analysis/analyzer/x509/X509.cc
+++ b/src/file_analysis/analyzer/x509/X509.cc
@@ -257,8 +257,8 @@ X509_STORE* file_analysis::X509::GetRootStore(TableVal* root_certs)
 		::X509* x = d2i_X509(NULL, &data, sv->Len());
 		if ( ! x )
 			{
-			builtin_error(fmt("Root CA error: %s", ERR_error_string(ERR_get_error(),NULL)));
-			return 0;
+			builtin_error(fmt("Root CA error: %s", ERR_error_string(ERR_get_error(), NULL)));
+			return nullptr;
 			}
 
 		X509_STORE_add_cert(ctx, x);
@@ -339,10 +339,10 @@ void file_analysis::X509::ParseSAN(X509_EXTENSION* ext)
 		return;
 		}
 
-	VectorVal* names = 0;
-	VectorVal* emails = 0;
-	VectorVal* uris = 0;
-	VectorVal* ips = 0;
+	VectorVal* names = nullptr;
+	VectorVal* emails = nullptr;
+	VectorVal* uris = nullptr;
+	VectorVal* ips = nullptr;
 
 	bool otherfields = false;
 
@@ -369,21 +369,21 @@ void file_analysis::X509::ParseSAN(X509_EXTENSION* ext)
 			switch ( gen->type )
 				{
 				case GEN_DNS:
-					if ( names == 0 )
+					if ( names == nullptr )
 						names = new VectorVal(internal_type("string_vec")->AsVectorType());
 
 					names->Assign(names->Size(), bs);
 					break;
 
 				case GEN_URI:
-					if ( uris == 0 )
+					if ( uris == nullptr )
 						uris = new VectorVal(internal_type("string_vec")->AsVectorType());
 
 					uris->Assign(uris->Size(), bs);
 					break;
 
 				case GEN_EMAIL:
-					if ( emails == 0 )
+					if ( emails == nullptr )
 						emails = new VectorVal(internal_type("string_vec")->AsVectorType());
 
 					emails->Assign(emails->Size(), bs);
@@ -393,7 +393,7 @@ void file_analysis::X509::ParseSAN(X509_EXTENSION* ext)
 
 		else if ( gen->type == GEN_IPADD )
 			{
-				if ( ips == 0 )
+				if ( ips == nullptr )
 					ips = new VectorVal(internal_type("addr_vec")->AsVectorType());
 
 				uint32_t* addr = (uint32_t*) gen->d.ip->data;
@@ -422,16 +422,16 @@ void file_analysis::X509::ParseSAN(X509_EXTENSION* ext)
 
 		auto sanExt = make_intrusive<RecordVal>(BifType::Record::X509::SubjectAlternativeName);
 
-		if ( names != 0 )
+		if ( names != nullptr )
 			sanExt->Assign(0, names);
 
-		if ( uris != 0 )
+		if ( uris != nullptr )
 			sanExt->Assign(1, uris);
 
-		if ( emails != 0 )
+		if ( emails != nullptr )
 			sanExt->Assign(2, emails);
 
-		if ( ips != 0 )
+		if ( ips != nullptr )
 			sanExt->Assign(3, ips);
 
 		sanExt->Assign(4, val_mgr->GetBool(otherfields));
@@ -453,23 +453,23 @@ StringVal* file_analysis::X509::KeyCurve(EVP_PKEY *key)
 	if ( EVP_PKEY_base_id(key) != EVP_PKEY_EC )
 		{
 		// no EC-key - no curve name
-		return NULL;
+		return nullptr;
 		}
 
 	const EC_GROUP *group;
 	int nid;
 	if ( (group = EC_KEY_get0_group(EVP_PKEY_get0_EC_KEY(key))) == NULL )
 		// I guess we could not parse this
-		return NULL;
+		return nullptr;
 
 	nid = EC_GROUP_get_curve_name(group);
 	if ( nid == 0 )
 		// and an invalid nid...
-		return NULL;
+		return nullptr;
 
 	const char * curve_name = OBJ_nid2sn(nid);
-	if ( curve_name == NULL )
-		return NULL;
+	if ( curve_name == nullptr )
+		return nullptr;
 
 	return new StringVal(curve_name);
 #endif
@@ -560,7 +560,7 @@ IMPLEMENT_OPAQUE_VALUE(X509Val)
 
 broker::expected<broker::data> X509Val::DoSerialize() const
 	{
-	unsigned char *buf = NULL;
+	unsigned char *buf = nullptr;
 	int length = i2d_X509(certificate, &buf);
 
 	if ( length < 0 )
diff --git a/src/file_analysis/analyzer/x509/X509.h b/src/file_analysis/analyzer/x509/X509.h
index 54f32b49f8..fd9934bd80 100644
--- a/src/file_analysis/analyzer/x509/X509.h
+++ b/src/file_analysis/analyzer/x509/X509.h
@@ -86,7 +86,7 @@ public:
 	 * @param Returns the new record value and passes ownership to
 	 * caller.
 	 */
-	static RecordVal* ParseCertificate(X509Val* cert_val, File* file = 0);
+	static RecordVal* ParseCertificate(X509Val* cert_val, File* file = nullptr);
 
 	static file_analysis::Analyzer* Instantiate(RecordVal* args, File* file)
 		{ return new X509(args, file); }
diff --git a/src/file_analysis/analyzer/x509/X509Common.cc b/src/file_analysis/analyzer/x509/X509Common.cc
index 86ab607707..c560e2afdb 100644
--- a/src/file_analysis/analyzer/x509/X509Common.cc
+++ b/src/file_analysis/analyzer/x509/X509Common.cc
@@ -310,7 +310,7 @@ IntrusivePtr<StringVal> file_analysis::X509Common::GetExtensionFromBIO(BIO* bio,
 		ERR_error_string_n(ERR_get_error(), tmp, sizeof(tmp));
 		EmitWeird("x509_get_ext_from_bio", f, tmp);
 		BIO_free_all(bio);
-		return 0;
+		return nullptr;
 		}
 
 	if ( length == 0 )
@@ -327,7 +327,7 @@ IntrusivePtr<StringVal> file_analysis::X509Common::GetExtensionFromBIO(BIO* bio,
 		// because it's unclear the length value is very reliable.
 		reporter->Error("X509::GetExtensionFromBIO malloc(%d) failed", length);
 		BIO_free_all(bio);
-		return 0;
+		return nullptr;
 		}
 
 	BIO_read(bio, (void*) buffer, length);
diff --git a/src/file_analysis/analyzer/x509/X509Common.h b/src/file_analysis/analyzer/x509/X509Common.h
index f8f934093e..da3fe3a1c2 100644
--- a/src/file_analysis/analyzer/x509/X509Common.h
+++ b/src/file_analysis/analyzer/x509/X509Common.h
@@ -35,7 +35,7 @@ public:
 	 *
 	 * @return The X509 extension value.
 	 */
-	static IntrusivePtr<StringVal> GetExtensionFromBIO(BIO* bio, File* f = 0);
+	static IntrusivePtr<StringVal> GetExtensionFromBIO(BIO* bio, File* f = nullptr);
 
 	static double GetTimeFromAsn1(const ASN1_TIME* atime, File* f, Reporter* reporter);
 
diff --git a/src/file_analysis/analyzer/x509/functions.bif b/src/file_analysis/analyzer/x509/functions.bif
index bdea24a15c..9f5635122f 100644
--- a/src/file_analysis/analyzer/x509/functions.bif
+++ b/src/file_analysis/analyzer/x509/functions.bif
@@ -11,7 +11,7 @@
 #include <openssl/err.h>
 
 // construct an error record
-RecordVal* x509_result_record(uint64_t num, const char* reason, Val* chainVector = 0)
+RecordVal* x509_result_record(uint64_t num, const char* reason, Val* chainVector = nullptr)
 	{
 	RecordVal* rrecord = new RecordVal(BifType::Record::X509::Result);
 
@@ -542,7 +542,7 @@ function x509_verify%(certs: x509_opaque_vector, root_certs: table_string_of_str
 
 	int result = X509_verify_cert(csc);
 
-	VectorVal* chainVector = 0;
+	VectorVal* chainVector = nullptr;
 
 	if ( result == 1 ) // we have a valid chain. try to get it...
 		{
diff --git a/src/input/Manager.cc b/src/input/Manager.cc
index 435ae03801..b8a5a4be37 100644
--- a/src/input/Manager.cc
+++ b/src/input/Manager.cc
@@ -166,13 +166,13 @@ Manager::TableStream::~TableStream()
 	if ( rtype ) // can be 0 for sets
 		Unref(rtype);
 
-	if ( currDict != 0 )
+	if ( currDict )
 		{
 		currDict->Clear();
 		delete currDict;
 		}
 
-	if ( lastDict != 0 )
+	if ( lastDict )
 		{
 		lastDict->Clear();;
 		delete lastDict;
@@ -211,7 +211,7 @@ ReaderBackend* Manager::CreateBackend(ReaderFrontend* frontend, EnumVal* tag)
 	if ( ! c )
 		{
 		reporter->Error("The reader that was requested was not found and could not be initialized.");
-		return 0;
+		return nullptr;
 		}
 
 	ReaderBackend* backend = (*c->Factory())(frontend);
@@ -234,8 +234,7 @@ bool Manager::CreateStream(Stream* info, RecordVal* description)
 
 	string name = description->Lookup("name", true)->AsString()->CheckString();
 
-	Stream *i = FindStream(name);
-	if ( i != 0 )
+	if ( Stream *i = FindStream(name) )
 		{
 		reporter->Error("Trying create already existing input stream %s",
 				name.c_str());
@@ -551,7 +550,7 @@ bool Manager::CreateTableStream(RecordVal* fval)
 		}
 
 	auto event_val = fval->Lookup("ev", true);
-	Func* event = event_val ? event_val->AsFunc() : 0;
+	Func* event = event_val ? event_val->AsFunc() : nullptr;
 
 	if ( event )
 		{
@@ -672,13 +671,13 @@ bool Manager::CreateTableStream(RecordVal* fval)
 	for ( unsigned int i = 0; i < fieldsV.size(); i++ )
 		fields[i] = fieldsV[i];
 
-	stream->pred = pred ? pred->AsFunc() : 0;
+	stream->pred = pred ? pred->AsFunc() : nullptr;
 	stream->num_idx_fields = idxfields;
 	stream->num_val_fields = valfields;
 	stream->tab = dst.release()->AsTableVal();
 	stream->rtype = val.release();
 	stream->itype = idx->Ref()->AsRecordType();
-	stream->event = event ? event_registry->Lookup(event->Name()) : 0;
+	stream->event = event ? event_registry->Lookup(event->Name()) : nullptr;
 	stream->error_event = error_event ? event_registry->Lookup(error_event->Name()) : nullptr;
 	stream->currDict = new PDict<InputHash>;
 	stream->currDict->SetDeleteFunc(input_hash_delete_func);
@@ -769,7 +768,7 @@ bool Manager::CreateAnalysisStream(RecordVal* fval)
 
 	// reader takes in a byte stream as the only field
 	Field** fields = new Field*[1];
-	fields[0] = new Field("bytestream", 0, TYPE_STRING, TYPE_VOID, false);
+	fields[0] = new Field("bytestream", nullptr, TYPE_STRING, TYPE_VOID, false);
 	stream->reader->Init(1, fields);
 
 	readers[stream->reader] = stream;
@@ -833,7 +832,7 @@ bool Manager::IsCompatibleType(BroType* t, bool atomic_only)
 
 bool Manager::RemoveStream(Stream *i)
 	{
-	if ( i == 0 )
+	if ( i == nullptr )
 		return false; // not found
 
 	if ( i->removed )
@@ -868,7 +867,7 @@ bool Manager::RemoveStreamContinuation(ReaderFrontend* reader)
 	{
 	Stream *i = FindStream(reader);
 
-	if ( i == 0 )
+	if ( i == nullptr )
 		{
 		reporter->Error("Stream not found in RemoveStreamContinuation");
 		return false;
@@ -934,7 +933,7 @@ bool Manager::UnrollRecordType(vector<Field*> *fields, const RecordType *rec,
 		else
 			{
 			string name = nameprepend + rec->FieldName(i);
-			const char* secondary = 0;
+			const char* secondary = nullptr;
 			IntrusivePtr<Val> c;
 			TypeTag ty = rec->FieldType(i)->Tag();
 			TypeTag st = TYPE_VOID;
@@ -951,7 +950,7 @@ bool Manager::UnrollRecordType(vector<Field*> *fields, const RecordType *rec,
 				{
 				// we have an annotation for the second column
 
-				c = rec->FieldDecl(i)->FindAttr(ATTR_TYPE_COLUMN)->AttrExpr()->Eval(0);
+				c = rec->FieldDecl(i)->FindAttr(ATTR_TYPE_COLUMN)->AttrExpr()->Eval(nullptr);
 
 				assert(c);
 				assert(c->Type()->Tag() == TYPE_STRING);
@@ -973,7 +972,7 @@ bool Manager::UnrollRecordType(vector<Field*> *fields, const RecordType *rec,
 bool Manager::ForceUpdate(const string &name)
 	{
 	Stream *i = FindStream(name);
-	if ( i == 0 )
+	if ( i == nullptr )
 		{
 		reporter->Error("Stream %s not found", name.c_str());
 		return false;
@@ -1057,7 +1056,7 @@ Val* Manager::ValueToIndexVal(const Stream* i, int num_fields, const RecordType
 void Manager::SendEntry(ReaderFrontend* reader, Value* *vals)
 	{
 	Stream *i = FindStream(reader);
-	if ( i == 0 )
+	if ( i == nullptr )
 		{
 		reporter->InternalWarning("Unknown reader %s in SendEntry",
 		                          reader->Name());
@@ -1101,7 +1100,7 @@ int Manager::SendEntryTable(Stream* i, const Value* const *vals)
 
 	HashKey* idxhash = HashValues(stream->num_idx_fields, vals);
 
-	if ( idxhash == 0 )
+	if ( idxhash == nullptr )
 		{
 		Warning(i, "Could not hash line. Ignoring");
 		return stream->num_val_fields + stream->num_idx_fields;
@@ -1110,21 +1109,20 @@ int Manager::SendEntryTable(Stream* i, const Value* const *vals)
 	hash_t valhash = 0;
 	if ( stream->num_val_fields > 0 )
 		{
-		HashKey* valhashkey = HashValues(stream->num_val_fields, vals+stream->num_idx_fields);
-		if ( valhashkey == 0 )
-			{
-			// empty line. index, but no values.
-			// hence we also have no hash value...
-			}
-		else
+		if ( HashKey* valhashkey = HashValues(stream->num_val_fields, vals+stream->num_idx_fields) )
 			{
 			valhash = valhashkey->Hash();
 			delete(valhashkey);
 			}
+		else
+			{
+			// empty line. index, but no values.
+			// hence we also have no hash value...
+			}
 		}
 
 	InputHash *h = stream->lastDict->Lookup(idxhash);
-	if ( h != 0 )
+	if ( h )
 		{
 		// seen before
 		if ( stream->num_val_fields == 0 || h->valhash == valhash )
@@ -1148,14 +1146,14 @@ int Manager::SendEntryTable(Stream* i, const Value* const *vals)
 		}
 
 	Val* valval;
-	RecordVal* predidx = 0;
+	RecordVal* predidx = nullptr;
 
 	int position = stream->num_idx_fields;
 
 	bool convert_error = false; // this will be set to true by ValueTo* on Error
 
 	if ( stream->num_val_fields == 0 )
-		valval = 0;
+		valval = nullptr;
 
 	else if ( stream->num_val_fields == 1 && !stream->want_record )
 		valval = ValueToVal(i, vals[position], stream->rtype->FieldType(0), convert_error);
@@ -1213,10 +1211,10 @@ int Manager::SendEntryTable(Stream* i, const Value* const *vals)
 
 	// now we don't need h anymore - if we are here, the entry is updated and a new h is created.
 	delete h;
-	h = 0;
+	h = nullptr;
 
 	Val* idxval;
-	if ( predidx != 0 )
+	if ( predidx != nullptr )
 		{
 		idxval = RecordValToIndexVal(predidx);
 		// I think there is an unref missing here. But if I insert is, it crashes :)
@@ -1256,7 +1254,7 @@ int Manager::SendEntryTable(Stream* i, const Value* const *vals)
 	stream->tab->Assign(idxval, k, valval);
 	Unref(idxval); // asssign does not consume idxval.
 
-	if ( predidx != 0 )
+	if ( predidx != nullptr )
 		Unref(predidx);
 
 	auto prev = stream->currDict->Insert(idxhash, ih);
@@ -1279,7 +1277,7 @@ int Manager::SendEntryTable(Stream* i, const Value* const *vals)
 			{ // in case of update send back the old value.
 			assert ( stream->num_val_fields > 0 );
 			ev = BifType::Enum::Input::Event->GetVal(BifEnum::Input::EVENT_CHANGED).release();
-			assert ( oldval != 0 );
+			assert ( oldval != nullptr );
 			SendEvent(stream->event, 4, stream->description->Ref(), ev, predidx, oldval.release());
 			}
 		else
@@ -1302,7 +1300,7 @@ void Manager::EndCurrentSend(ReaderFrontend* reader)
 	{
 	Stream *i = FindStream(reader);
 
-	if ( i == 0 )
+	if ( i == nullptr )
 		{
 		reporter->InternalWarning("Unknown reader %s in EndCurrentSend",
 		                          reader->Name());
@@ -1336,8 +1334,8 @@ void Manager::EndCurrentSend(ReaderFrontend* reader)
 		{
 		IntrusivePtr<Val> val;
 
-		Val* predidx = 0;
-		EnumVal* ev = 0;
+		Val* predidx = nullptr;
+		EnumVal* ev = nullptr;
 		int startpos = 0;
 
 		if ( stream->pred || stream->event )
@@ -1345,7 +1343,7 @@ void Manager::EndCurrentSend(ReaderFrontend* reader)
 			auto idx = stream->tab->RecoverIndex(ih->idxkey);
 			assert(idx != nullptr);
 			val = stream->tab->Lookup(idx.get());
-			assert(val != 0);
+			assert(val != nullptr);
 			predidx = ListValToRecordVal(idx.get(), stream->itype, &startpos);
 			ev = BifType::Enum::Input::Event->GetVal(BifEnum::Input::EVENT_REMOVED).release();
 			}
@@ -1409,7 +1407,7 @@ void Manager::SendEndOfData(ReaderFrontend* reader)
 	{
 	Stream *i = FindStream(reader);
 
-	if ( i == 0 )
+	if ( i == nullptr )
 		{
 		reporter->InternalWarning("Unknown reader %s in SendEndOfData",
 		                          reader->Name());
@@ -1436,7 +1434,7 @@ void Manager::SendEndOfData(const Stream *i)
 void Manager::Put(ReaderFrontend* reader, Value* *vals)
 	{
 	Stream *i = FindStream(reader);
-	if ( i == 0 )
+	if ( i == nullptr )
 		{
 		reporter->InternalWarning("Unknown reader %s in Put", reader->Name());
 		return;
@@ -1500,7 +1498,7 @@ int Manager::SendEventStreamEvent(Stream* i, EnumVal* type, const Value* const *
 		{
 		for ( int j = 0; j < stream->fields->NumFields(); j++)
 			{
-			Val* val = 0;
+			Val* val = nullptr;
 
 			if ( stream->fields->FieldType(j)->Tag() == TYPE_RECORD )
 				val = ValueToRecordVal(i, vals,
@@ -1544,7 +1542,7 @@ int Manager::PutTable(Stream* i, const Value* const *vals)
 	int position = stream->num_idx_fields;
 
 	if ( stream->num_val_fields == 0 )
-		valval = 0;
+		valval = nullptr;
 
 	else if ( stream->num_val_fields == 1 && stream->want_record == 0 )
 		valval = ValueToVal(i, vals[position], stream->rtype->FieldType(0), convert_error);
@@ -1571,7 +1569,7 @@ int Manager::PutTable(Stream* i, const Value* const *vals)
 			oldval = stream->tab->Lookup(idxval, false);
 			}
 
-		if ( oldval != 0 )
+		if ( oldval != nullptr )
 			{
 			// it is an update
 			updated = true;
@@ -1633,7 +1631,7 @@ int Manager::PutTable(Stream* i, const Value* const *vals)
 					// in case of update send back the old value.
 					assert ( stream->num_val_fields > 0 );
 					ev = BifType::Enum::Input::Event->GetVal(BifEnum::Input::EVENT_CHANGED).release();
-					assert ( oldval != 0 );
+					assert ( oldval != nullptr );
 					SendEvent(stream->event, 4, stream->description->Ref(),
 					          ev, predidx, oldval.release());
 					}
@@ -1665,7 +1663,7 @@ int Manager::PutTable(Stream* i, const Value* const *vals)
 void Manager::Clear(ReaderFrontend* reader)
 	{
 	Stream *i = FindStream(reader);
-	if ( i == 0 )
+	if ( i == nullptr )
 		{
 		reporter->InternalWarning("Unknown reader %s in Clear",
 		                          reader->Name());
@@ -1687,7 +1685,7 @@ void Manager::Clear(ReaderFrontend* reader)
 bool Manager::Delete(ReaderFrontend* reader, Value* *vals)
 	{
 	Stream *i = FindStream(reader);
-	if ( i == 0 )
+	if ( i == nullptr )
 		{
 		reporter->InternalWarning("Unknown reader %s in Delete", reader->Name());
 		return false;
@@ -1701,7 +1699,7 @@ bool Manager::Delete(ReaderFrontend* reader, Value* *vals)
 		TableStream* stream = (TableStream*) i;
 		bool convert_error = false;
 		Val* idxval = ValueToIndexVal(i, stream->num_idx_fields, stream->itype, vals, convert_error);
-		assert(idxval != 0);
+		assert(idxval != nullptr);
 		readVals = stream->num_idx_fields + stream->num_val_fields;
 		bool streamresult = true;
 
@@ -1742,7 +1740,7 @@ bool Manager::Delete(ReaderFrontend* reader, Value* *vals)
 			if ( streamresult && stream->event )
 				{
 				Ref(idxval);
-				assert(val != 0);
+				assert(val != nullptr);
 				EnumVal* ev = BifType::Enum::Input::Event->GetVal(BifEnum::Input::EVENT_REMOVED).release();
 				SendEvent(stream->event, 4, stream->description->Ref(), ev, idxval, IntrusivePtr{val}.release());
 				}
@@ -1806,7 +1804,7 @@ bool Manager::CallPred(Func* pred_func, const int numvals, ...) const
 bool Manager::SendEvent(ReaderFrontend* reader, const string& name, const int num_vals, Value* *vals) const
 	{
 	Stream *i = FindStream(reader);
-	if ( i == 0 )
+	if ( i == nullptr )
 		{
 		reporter->InternalWarning("Unknown reader %s in SendEvent for event %s", reader->Name(), name.c_str());
 		delete_value_ptr_array(vals, num_vals);
@@ -1814,7 +1812,7 @@ bool Manager::SendEvent(ReaderFrontend* reader, const string& name, const int nu
 		}
 
 	EventHandler* handler = event_registry->Lookup(name);
-	if ( handler == 0 )
+	if ( handler == nullptr )
 		{
 		Warning(i, "Event %s not found", name.c_str());
 		delete_value_ptr_array(vals, num_vals);
@@ -1904,18 +1902,18 @@ void Manager::SendEvent(EventHandlerPtr ev, list<Val*> events) const
 // I / we could think about moving this functionality to val.cc
 RecordVal* Manager::ListValToRecordVal(ListVal* list, RecordType *request_type, int* position) const
 	{
-	assert(position != 0 ); // we need the pointer to point to data;
+	assert(position != nullptr); // we need the pointer to point to data;
 
 	RecordVal* rec = new RecordVal(request_type->AsRecordType());
 
-	assert(list != 0);
+	assert(list != nullptr);
 	int maxpos = list->Length();
 
 	for ( int i = 0; i < request_type->NumFields(); i++ )
 		{
 		assert ( (*position) <= maxpos );
 
-		Val* fieldVal = 0;
+		Val* fieldVal = nullptr;
 		if ( request_type->FieldType(i)->Tag() == TYPE_RECORD )
 			fieldVal = ListValToRecordVal(list, request_type->FieldType(i)->AsRecordType(), position);
 		else
@@ -1934,12 +1932,12 @@ RecordVal* Manager::ListValToRecordVal(ListVal* list, RecordType *request_type,
 RecordVal* Manager::ValueToRecordVal(const Stream* stream, const Value* const *vals,
 	                             RecordType *request_type, int* position, bool& have_error) const
 	{
-	assert(position != 0); // we need the pointer to point to data.
+	assert(position != nullptr); // we need the pointer to point to data.
 
 	RecordVal* rec = new RecordVal(request_type->AsRecordType());
 	for ( int i = 0; i < request_type->NumFields(); i++ )
 		{
-		Val* fieldVal = 0;
+		Val* fieldVal = nullptr;
 		if ( request_type->FieldType(i)->Tag() == TYPE_RECORD )
 			fieldVal = ValueToRecordVal(stream, vals, request_type->FieldType(i)->AsRecordType(), position, have_error);
 		else if ( request_type->FieldType(i)->Tag() == TYPE_FILE ||
@@ -2215,7 +2213,7 @@ HashKey* Manager::HashValues(const int num_elements, const Value* const *vals) c
 	assert ( length >= num_elements );
 
 	if ( length == num_elements )
-		return NULL;
+		return nullptr;
 
 	int position = 0;
 	char *data = new char[length];
@@ -2285,7 +2283,7 @@ Val* Manager::ValueToVal(const Stream* i, const Value* val, BroType* request_typ
 
 	case TYPE_ADDR:
 		{
-		IPAddr* addr = 0;
+		IPAddr* addr = nullptr;
 		switch ( val->val.addr_val.family ) {
 		case IPv4:
 			addr = new IPAddr(val->val.addr_val.in.in4);
@@ -2344,7 +2342,7 @@ Val* Manager::ValueToVal(const Stream* i, const Value* val, BroType* request_typ
 			{
 			Val* assignval = ValueToVal(i, val->val.set_val.vals[j], type, have_error);
 
-			t->Assign(assignval, 0);
+			t->Assign(assignval, nullptr);
 			Unref(assignval); // index is not consumed by assign.
 			}
 
@@ -2395,7 +2393,7 @@ Val* Manager::ValueToVal(const Stream* i, const Value* val, BroType* request_typ
 	}
 
 	assert(false);
-	return NULL;
+	return nullptr;
 	}
 
 Val* Manager::ValueToVal(const Stream* i, const Value* val, bool& have_error) const
@@ -2433,7 +2431,7 @@ Val* Manager::ValueToVal(const Stream* i, const Value* val, bool& have_error) co
 
 	case TYPE_ADDR:
 		{
-		IPAddr* addr = 0;
+		IPAddr* addr = nullptr;
 		switch ( val->val.addr_val.family ) {
 		case IPv4:
 			addr = new IPAddr(val->val.addr_val.in.in4);
@@ -2526,7 +2524,7 @@ Val* Manager::ValueToVal(const Stream* i, const Value* val, bool& have_error) co
 			{
 			Val* assignval = ValueToVal(i, val->val.set_val.vals[j], have_error);
 
-			t->Assign(assignval, 0);
+			t->Assign(assignval, nullptr);
 			Unref(assignval); // index is not consumed by assign.
 			}
 
@@ -2593,7 +2591,7 @@ Val* Manager::ValueToVal(const Stream* i, const Value* val, bool& have_error) co
 	}
 
 	assert(false);
-	return NULL;
+	return nullptr;
 	}
 
 Manager::Stream* Manager::FindStream(const string &name) const
@@ -2604,7 +2602,7 @@ Manager::Stream* Manager::FindStream(const string &name) const
 			return (*s).second;
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 Manager::Stream* Manager::FindStream(ReaderFrontend* reader) const
@@ -2613,7 +2611,7 @@ Manager::Stream* Manager::FindStream(ReaderFrontend* reader) const
 	if ( s != readers.end() )
 		return s->second;
 
-	return 0;
+	return nullptr;
 	}
 
 // Function is called on Bro shutdown.
diff --git a/src/input/ReaderBackend.cc b/src/input/ReaderBackend.cc
index 656743abb5..90050a6438 100644
--- a/src/input/ReaderBackend.cc
+++ b/src/input/ReaderBackend.cc
@@ -204,7 +204,7 @@ ReaderBackend::ReaderBackend(ReaderFrontend* arg_frontend) : MsgThread()
 	frontend = arg_frontend;
 	info = new ReaderInfo(frontend->Info());
 	num_fields = 0;
-	fields = 0;
+	fields = nullptr;
 
 	SetName(frontend->Name());
 	}
@@ -282,13 +282,13 @@ bool ReaderBackend::OnFinish(double network_time)
 	disabled = true; // frontend disables itself when it gets the Close-message.
 	SendOut(new ReaderClosedMessage(frontend));
 
-	if ( fields != 0 )
+	if ( fields )
 		{
 		for ( unsigned int i = 0; i < num_fields; i++ )
 			delete(fields[i]);
 
 		delete [] (fields);
-		fields = 0;
+		fields = nullptr;
 		}
 
 	return true;
diff --git a/src/input/ReaderBackend.h b/src/input/ReaderBackend.h
index 3219359f71..d158d0972c 100644
--- a/src/input/ReaderBackend.h
+++ b/src/input/ReaderBackend.h
@@ -104,15 +104,15 @@ public:
 
 		ReaderInfo()
 			{
-			source = 0;
-			name = 0;
+			source = nullptr;
+			name = nullptr;
 			mode = MODE_NONE;
 			}
 
 		ReaderInfo(const ReaderInfo& other)
 			{
-			source = other.source ? copy_string(other.source) : 0;
-			name = other.name ? copy_string(other.name) : 0;
+			source = other.source ? copy_string(other.source) : nullptr;
+			name = other.name ? copy_string(other.name) : nullptr;
 			mode = other.mode;
 
 			for ( config_map::const_iterator i = other.config.begin(); i != other.config.end(); i++ )
diff --git a/src/input/ReaderFrontend.cc b/src/input/ReaderFrontend.cc
index 898d4b30da..7fce36ee71 100644
--- a/src/input/ReaderFrontend.cc
+++ b/src/input/ReaderFrontend.cc
@@ -52,7 +52,7 @@ void ReaderFrontend::Stop()
 	if ( backend )
 		{
 		backend->SignalStop();
-		backend = 0; // Thread manager will clean it up once it finishes.
+		backend = nullptr; // Thread manager will clean it up once it finishes.
 		}
 	}
 
diff --git a/src/input/readers/ascii/Ascii.cc b/src/input/readers/ascii/Ascii.cc
index 2bf2cff996..d04fbe713d 100644
--- a/src/input/readers/ascii/Ascii.cc
+++ b/src/input/readers/ascii/Ascii.cc
@@ -396,7 +396,7 @@ bool Ascii::DoUpdate()
 
 			Value* val = formatter->ParseValue(stringfields[(*fit).position], (*fit).name, (*fit).type, (*fit).subtype);
 
-			if ( val == 0 )
+			if ( ! val )
 				{
 				Warning(Fmt("Could not convert line '%s' of %s to Val. Ignoring line.", line.c_str(), fname.c_str()));
 				error = true;
diff --git a/src/input/readers/benchmark/Benchmark.cc b/src/input/readers/benchmark/Benchmark.cc
index 49e989909c..32d57787c1 100644
--- a/src/input/readers/benchmark/Benchmark.cc
+++ b/src/input/readers/benchmark/Benchmark.cc
@@ -210,11 +210,11 @@ threading::Value* Benchmark::EntryToVal(TypeTag type, TypeTag subtype)
 		for ( unsigned int pos = 0; pos < length; pos++ )
 			{
 			Value* newval = EntryToVal(subtype, TYPE_ENUM);
-			if ( newval == 0 )
+			if ( newval == nullptr )
 				{
 				Error("Error while reading set");
 				delete val;
-				return 0;
+				return nullptr;
 				}
 			lvals[pos] = newval;
 			}
@@ -226,7 +226,7 @@ threading::Value* Benchmark::EntryToVal(TypeTag type, TypeTag subtype)
 	default:
 		Error(Fmt("unsupported field format %d", type));
 		delete val;
-		return 0;
+		return nullptr;
 	}
 
 	return val;
@@ -265,7 +265,7 @@ bool Benchmark::DoHeartbeat(double network_time, double current_time)
 
 			Update(); // call update and not DoUpdate, because update actually checks disabled.
 
-			SendEvent("HeartbeatDone", 0, 0);
+			SendEvent("HeartbeatDone", 0, nullptr);
 			break;
 
 		default:
diff --git a/src/input/readers/binary/Binary.cc b/src/input/readers/binary/Binary.cc
index 87c38d16aa..22a7121e13 100644
--- a/src/input/readers/binary/Binary.cc
+++ b/src/input/readers/binary/Binary.cc
@@ -14,7 +14,7 @@ using threading::Field;
 streamsize Binary::chunk_size = 0;
 
 Binary::Binary(ReaderFrontend *frontend)
-	: ReaderBackend(frontend), in(0), mtime(0), ino(0), firstrun(true)
+	: ReaderBackend(frontend), in(nullptr), mtime(0), ino(0), firstrun(true)
 	{
 	if ( ! chunk_size )
 		{
@@ -64,7 +64,7 @@ bool Binary::CloseInput()
 
 	in->close();
 	delete in;
-	in = 0;
+	in = nullptr;
 
 #ifdef DEBUG
 	Debug(DBG_INPUT, "Binary reader finished close");
@@ -76,7 +76,7 @@ bool Binary::CloseInput()
 bool Binary::DoInit(const ReaderInfo& info, int num_fields,
                     const Field* const* fields)
 	{
-	in = 0;
+	in = nullptr;
 	mtime = 0;
 	ino = 0;
 	firstrun = true;
@@ -158,7 +158,7 @@ streamsize Binary::GetChunk(char** chunk)
 	if ( ! bytes_read )
 		{
 		delete [] *chunk;
-		*chunk = 0;
+		*chunk = nullptr;
 		return 0;
 		}
 
@@ -231,7 +231,7 @@ bool Binary::DoUpdate()
 		}
 		}
 
-	char* chunk = 0;
+	char* chunk = nullptr;
 	streamsize size = 0;
 	while ( (size = GetChunk(&chunk)) )
 		{
diff --git a/src/input/readers/sqlite/SQLite.cc b/src/input/readers/sqlite/SQLite.cc
index 821e6cdd9a..e831db8c62 100644
--- a/src/input/readers/sqlite/SQLite.cc
+++ b/src/input/readers/sqlite/SQLite.cc
@@ -156,7 +156,7 @@ Value* SQLite::EntryToVal(sqlite3_stmt *st, const threading::Field *field, int p
 			{
 			Error("Invalid data type for boolean - expected Integer");
 			delete val;
-			return 0;
+			return nullptr;
 			}
 
 		int res = sqlite3_column_int(st, pos);
@@ -167,7 +167,7 @@ Value* SQLite::EntryToVal(sqlite3_stmt *st, const threading::Field *field, int p
 			{
 			Error(Fmt("Invalid value for boolean: %d", res));
 			delete val;
-			return 0;
+			return nullptr;
 			}
 		break;
 		}
@@ -240,7 +240,7 @@ Value* SQLite::EntryToVal(sqlite3_stmt *st, const threading::Field *field, int p
 	default:
 		Error(Fmt("unsupported field format %d", field->type));
 		delete val;
-		return 0;
+		return nullptr;
 	}
 
 	return val;
@@ -279,7 +279,7 @@ bool SQLite::DoUpdate()
 				mapping[j] = i;
 				}
 
-			if ( fields[j]->secondary_name != 0 && strcmp(fields[j]->secondary_name, name) == 0 )
+			if ( fields[j]->secondary_name != nullptr && strcmp(fields[j]->secondary_name, name) == 0 )
 				{
 				assert(fields[j]->type == TYPE_PORT);
 				if ( submapping[j] != -1 )
@@ -314,7 +314,7 @@ bool SQLite::DoUpdate()
 		for ( unsigned int j = 0; j < num_fields; ++j)
 			{
 			ofields[j] = EntryToVal(st, fields[j], mapping[j], submapping[j]);
-			if ( ofields[j] == 0 )
+			if ( ! ofields[j] )
 				{
 				for ( unsigned int k = 0; k < j; ++k )
 					delete ofields[k];
diff --git a/src/iosource/BPF_Program.cc b/src/iosource/BPF_Program.cc
index 8a97a6fc25..165b2fa2b2 100644
--- a/src/iosource/BPF_Program.cc
+++ b/src/iosource/BPF_Program.cc
@@ -143,7 +143,7 @@ bool BPF_Program::Compile(int snaplen, int linktype, const char* filter,
 
 bpf_program* BPF_Program::GetProgram()
 	{
-	return m_compiled ? &m_program : 0;
+	return m_compiled ? &m_program : nullptr;
 	}
 
 void BPF_Program::FreeCode()
diff --git a/src/iosource/BPF_Program.h b/src/iosource/BPF_Program.h
index de06e9d13a..0ff37bfd1f 100644
--- a/src/iosource/BPF_Program.h
+++ b/src/iosource/BPF_Program.h
@@ -22,14 +22,14 @@ public:
 	// Parameters are like in pcap_compile(). Returns true
 	// for successful compilation, false otherwise.
 	bool Compile(pcap_t* pcap, const char* filter, uint32_t netmask,
-		 char* errbuf = 0, unsigned int errbuf_len = 0,
+		 char* errbuf = nullptr, unsigned int errbuf_len = 0,
 		 bool optimize = true);
 
 	// Creates a BPF program when no pcap handle is around,
 	// similarly to pcap_compile_nopcap(). Parameters are
 	// similar. Returns true on success.
 	bool Compile(int snaplen, int linktype, const char* filter,
-		uint32_t netmask, char* errbuf = 0, unsigned int errbuf_len = 0,
+		uint32_t netmask, char* errbuf = nullptr, unsigned int errbuf_len = 0,
 		bool optimize = true);
 
 	// Returns true if this program currently contains compiled
diff --git a/src/iosource/Manager.cc b/src/iosource/Manager.cc
index 6bfa1ad420..217bdf0f8a 100644
--- a/src/iosource/Manager.cc
+++ b/src/iosource/Manager.cc
@@ -330,7 +330,7 @@ PktSrc* Manager::OpenPktSrc(const std::string& path, bool is_live)
 
 	// Find the component providing packet sources of the requested prefix.
 
-	PktSrcComponent* component = 0;
+	PktSrcComponent* component = nullptr;
 
 	std::list<PktSrcComponent*> all_components = plugin_mgr->Components<PktSrcComponent>();
 	for ( const auto& c : all_components )
@@ -372,7 +372,7 @@ PktDumper* Manager::OpenPktDumper(const string& path, bool append)
 
 	// Find the component providing packet dumpers of the requested prefix.
 
-	PktDumperComponent* component = 0;
+	PktDumperComponent* component = nullptr;
 
 	std::list<PktDumperComponent*> all_components = plugin_mgr->Components<PktDumperComponent>();
 	for ( const auto& c : all_components )
diff --git a/src/iosource/Packet.h b/src/iosource/Packet.h
index 4913514678..2da4836b7b 100644
--- a/src/iosource/Packet.h
+++ b/src/iosource/Packet.h
@@ -59,7 +59,7 @@ public:
 	Packet(int link_type, pkt_timeval *ts, uint32_t caplen,
 	       uint32_t len, const u_char *data, bool copy = false,
 	       std::string tag = std::string(""))
-	           : data(0), l2_src(0), l2_dst(0)
+	           : data(nullptr), l2_src(nullptr), l2_dst(nullptr)
 	       {
 	       Init(link_type, ts, caplen, len, data, copy, tag);
 	       }
@@ -67,10 +67,10 @@ public:
 	/**
 	 * Default constructor. For internal use only.
 	 */
-	Packet() : data(0), l2_src(0), l2_dst(0)
+	Packet() : data(nullptr), l2_src(nullptr), l2_dst(nullptr)
 		{
 		pkt_timeval ts = {0, 0};
-		Init(0, &ts, 0, 0, 0);
+		Init(0, &ts, 0, 0, nullptr);
 		}
 
 	/**
diff --git a/src/iosource/PktDumper.cc b/src/iosource/PktDumper.cc
index 9a49ccb6fb..f0d911b9b4 100644
--- a/src/iosource/PktDumper.cc
+++ b/src/iosource/PktDumper.cc
@@ -45,12 +45,12 @@ double PktDumper::OpenTime() const
 
 bool PktDumper::IsError() const
 	{
-	return errmsg.size();
+	return ! errmsg.empty();
 	}
 
 const char* PktDumper::ErrorMsg() const
 	{
-	return errmsg.size() ? errmsg.c_str() : 0;
+	return errmsg.size() ? errmsg.c_str() : nullptr;
 	}
 
 int PktDumper::HdrSize() const
diff --git a/src/iosource/PktSrc.cc b/src/iosource/PktSrc.cc
index 19bf1f3f52..53c2a747aa 100644
--- a/src/iosource/PktSrc.cc
+++ b/src/iosource/PktSrc.cc
@@ -51,7 +51,7 @@ const std::string& PktSrc::Path() const
 
 const char* PktSrc::ErrorMsg() const
 	{
-	return errbuf.size() ? errbuf.c_str() : 0;
+	return errbuf.size() ? errbuf.c_str() : nullptr;
 	}
 
 int PktSrc::LinkType() const
@@ -66,7 +66,7 @@ uint32_t PktSrc::Netmask() const
 
 bool PktSrc::IsError() const
 	{
-	return ErrorMsg();
+	return ! errbuf.empty();
 	}
 
 bool PktSrc::IsLive() const
@@ -153,7 +153,7 @@ void PktSrc::Info(const std::string& msg)
 
 void PktSrc::Weird(const std::string& msg, const Packet* p)
 	{
-	sessions->Weird(msg.c_str(), p, 0);
+	sessions->Weird(msg.c_str(), p, nullptr);
 	}
 
 void PktSrc::InternalError(const std::string& msg)
@@ -299,9 +299,9 @@ bool PktSrc::PrecompileBPFFilter(int index, const std::string& filter)
 BPF_Program* PktSrc::GetBPFFilter(int index)
 	{
 	if ( index < 0 )
-		return 0;
+		return nullptr;
 
-	return (static_cast<int>(filters.size()) > index ? filters[index] : 0);
+	return (static_cast<int>(filters.size()) > index ? filters[index] : nullptr);
 	}
 
 bool PktSrc::ApplyBPFFilter(int index, const struct pcap_pkthdr *hdr, const u_char *pkt)
diff --git a/src/iosource/pcap/Dumper.cc b/src/iosource/pcap/Dumper.cc
index e6e400477e..5bbf12dfa6 100644
--- a/src/iosource/pcap/Dumper.cc
+++ b/src/iosource/pcap/Dumper.cc
@@ -15,8 +15,8 @@ PcapDumper::PcapDumper(const std::string& path, bool arg_append)
 	{
 	append = arg_append;
 	props.path = path;
-	dumper = 0;
-	pd = 0;
+	dumper = nullptr;
+	pd = nullptr;
 	}
 
 PcapDumper::~PcapDumper()
@@ -93,8 +93,8 @@ void PcapDumper::Close()
 
 	pcap_dump_close(dumper);
 	pcap_close(pd);
-	dumper = 0;
-	pd = 0;
+	dumper = nullptr;
+	pd = nullptr;
 
 	Closed();
 	}
diff --git a/src/iosource/pcap/Source.h b/src/iosource/pcap/Source.h
index f32071cb99..24271b6613 100644
--- a/src/iosource/pcap/Source.h
+++ b/src/iosource/pcap/Source.h
@@ -33,7 +33,7 @@ protected:
 private:
 	void OpenLive();
 	void OpenOffline();
-	void PcapError(const char* where = 0);
+	void PcapError(const char* where = nullptr);
 
 	Properties props;
 	Stats stats;
diff --git a/src/logging/Manager.cc b/src/logging/Manager.cc
index 0ed09bbbeb..92485a7777 100644
--- a/src/logging/Manager.cc
+++ b/src/logging/Manager.cc
@@ -147,7 +147,7 @@ WriterBackend* Manager::CreateBackend(WriterFrontend* frontend, EnumVal* tag)
 	if ( ! c )
 		{
 		reporter->Error("unknown writer type requested");
-		return 0;
+		return nullptr;
 		}
 
 	WriterBackend* backend = (*c->Factory())(frontend);
@@ -161,7 +161,7 @@ Manager::Stream* Manager::FindStream(EnumVal* id)
 	unsigned int idx = id->AsEnum();
 
 	if ( idx >= streams.size() || ! streams[idx] )
-		return 0;
+		return nullptr;
 
 	return streams[idx];
 	}
@@ -182,7 +182,7 @@ Manager::WriterInfo* Manager::FindWriter(WriterFrontend* writer)
 			}
 		}
 
-	return 0;
+	return nullptr;
 	}
 
 bool Manager::CompareFields(const Filter* filter, const WriterFrontend* writer)
@@ -264,7 +264,7 @@ bool Manager::CreateStream(EnumVal* id, RecordVal* sval)
 		}
 
 	auto event_val = sval->Lookup("ev");
-	Func* event = event_val ? event_val->AsFunc() : 0;
+	Func* event = event_val ? event_val->AsFunc() : nullptr;
 
 	if ( event )
 		{
@@ -298,7 +298,7 @@ bool Manager::CreateStream(EnumVal* id, RecordVal* sval)
 	unsigned int idx = id->AsEnum();
 
 	while ( idx >= streams.size() )
-		streams.push_back(0);
+		streams.push_back(nullptr);
 
 	if ( streams[idx] )
 		// We already know this one, delete the previous definition.
@@ -309,7 +309,7 @@ bool Manager::CreateStream(EnumVal* id, RecordVal* sval)
 	streams[idx]->id = id->Ref()->AsEnumVal();
 	streams[idx]->enabled = true;
 	streams[idx]->name = id->Type()->AsEnumType()->Lookup(idx);
-	streams[idx]->event = event ? event_registry->Lookup(event->Name()) : 0;
+	streams[idx]->event = event ? event_registry->Lookup(event->Name()) : nullptr;
 	streams[idx]->columns = columns->Ref()->AsRecordType();
 
 	streams[idx]->enable_remote = internal_val("Log::enable_remote_logging")->AsBool();
@@ -347,7 +347,7 @@ bool Manager::RemoveStream(EnumVal* id)
 	stream->writers.clear();
 	string sname(stream->name);
 	delete stream;
-	streams[idx] = 0;
+	streams[idx] = nullptr;
 
 	DBG_LOG(DBG_LOGGING, "Removed logging stream '%s'", sname.c_str());
 	return true;
@@ -523,7 +523,7 @@ bool Manager::TraverseRecord(Stream* stream, Filter* filter, RecordType* rt,
 
 		bool optional = rtype->FieldDecl(i)->FindAttr(ATTR_OPTIONAL);
 
-		filter->fields[filter->num_fields - 1] = new threading::Field(new_path.c_str(), 0, t->Tag(), st, optional);
+		filter->fields[filter->num_fields - 1] = new threading::Field(new_path.c_str(), nullptr, t->Tag(), st, optional);
 		}
 
 	return true;
@@ -565,18 +565,18 @@ bool Manager::AddFilter(EnumVal* id, RecordVal* fval)
 	filter->fval = fval->Ref();
 	filter->name = name->AsString()->CheckString();
 	filter->id = id->Ref()->AsEnumVal();
-	filter->pred = pred ? pred->AsFunc() : 0;
-	filter->path_func = path_func ? path_func->AsFunc() : 0;
+	filter->pred = pred ? pred->AsFunc() : nullptr;
+	filter->path_func = path_func ? path_func->AsFunc() : nullptr;
 	filter->writer = writer->Ref()->AsEnumVal();
 	filter->local = log_local->AsBool();
 	filter->remote = log_remote->AsBool();
 	filter->interval = interv->AsInterval();
-	filter->postprocessor = postprocessor ? postprocessor->AsFunc() : 0;
+	filter->postprocessor = postprocessor ? postprocessor->AsFunc() : nullptr;
 	filter->config = config->Ref()->AsTableVal();
 	filter->field_name_map = field_name_map->Ref()->AsTableVal();
 	filter->scope_sep = scope_sep->AsString()->CheckString();
 	filter->ext_prefix = ext_prefix->AsString()->CheckString();
-	filter->ext_func = ext_func ? ext_func->AsFunc() : 0;
+	filter->ext_func = ext_func ? ext_func->AsFunc() : nullptr;
 
 	// Build the list of fields that the filter wants included, including
 	// potentially rolling out fields.
@@ -604,7 +604,7 @@ bool Manager::AddFilter(EnumVal* id, RecordVal* fval)
 		}
 
 	filter->num_fields = 0;
-	filter->fields = 0;
+	filter->fields = nullptr;
 	if ( ! TraverseRecord(stream, filter, stream->columns,
 			      include ? include->AsTableVal() : nullptr,
 			      exclude ? exclude->AsTableVal() : nullptr,
@@ -627,7 +627,7 @@ bool Manager::AddFilter(EnumVal* id, RecordVal* fval)
 		{
 		// If no path is given, it's derived based upon the value returned by
 		// the first call to the filter's path_func (during first write).
-		filter->path_val = 0;
+		filter->path_val = nullptr;
 		}
 
 	// Remove any filter with the same name we might already have.
@@ -811,8 +811,8 @@ bool Manager::Write(EnumVal* id, RecordVal* columns_arg)
 			path = filter->path = filter->path_val->AsString()->CheckString();
 			}
 
-		WriterBackend::WriterInfo* info = 0;
-		WriterFrontend* writer = 0;
+		WriterBackend::WriterInfo* info = nullptr;
+		WriterFrontend* writer = nullptr;
 
 		if ( w != stream->writers.end() )
 			{
@@ -1125,7 +1125,7 @@ WriterFrontend* Manager::CreateWriter(EnumVal* id, EnumVal* writer, WriterBacken
 				int num_fields, const threading::Field* const* fields, bool local, bool remote, bool from_remote,
 				const string& instantiating_filter)
 	{
-	WriterFrontend* result = 0;
+	WriterFrontend* result = nullptr;
 
 	Stream* stream = FindStream(id);
 
@@ -1133,7 +1133,7 @@ WriterFrontend* Manager::CreateWriter(EnumVal* id, EnumVal* writer, WriterBacken
 		{
 		// Don't know this stream.
 		delete_info_and_fields(info, num_fields, fields);
-		return 0;
+		return nullptr;
 		}
 
 	Stream::WriterMap::iterator w =
@@ -1149,11 +1149,11 @@ WriterFrontend* Manager::CreateWriter(EnumVal* id, EnumVal* writer, WriterBacken
 
 	WriterInfo* winfo = new WriterInfo;
 	winfo->type = writer->Ref()->AsEnumVal();
-	winfo->writer = 0;
+	winfo->writer = nullptr;
 	winfo->open_time = network_time;
-	winfo->rotation_timer = 0;
+	winfo->rotation_timer = nullptr;
 	winfo->interval = 0;
-	winfo->postprocessor = 0;
+	winfo->postprocessor = nullptr;
 	winfo->info = info;
 	winfo->from_remote = from_remote;
 	winfo->hook_initialized = false;
@@ -1194,7 +1194,7 @@ WriterFrontend* Manager::CreateWriter(EnumVal* id, EnumVal* writer, WriterBacken
 	// Still need to set the WriterInfo's rotation parameters, which we
 	// computed above.
 	const char* base_time = log_rotate_base_time ?
-		log_rotate_base_time->AsString()->CheckString() : 0;
+		log_rotate_base_time->AsString()->CheckString() : nullptr;
 
 	winfo->info->rotation_interval = winfo->interval;
 	winfo->info->rotation_base = parse_rotate_base_time(base_time);
@@ -1411,12 +1411,12 @@ protected:
 RotationTimer::~RotationTimer()
 	{
 	if ( winfo->rotation_timer == this )
-		winfo->rotation_timer = 0;
+		winfo->rotation_timer = nullptr;
 	}
 
 void RotationTimer::Dispatch(double t, bool is_expire)
 	{
-	winfo->rotation_timer = 0;
+	winfo->rotation_timer = nullptr;
 
 	if ( rotate )
 		log_mgr->Rotate(winfo);
@@ -1436,7 +1436,7 @@ void Manager::InstallRotationTimer(WriterInfo* winfo)
 	if ( winfo->rotation_timer )
 		{
 		timer_mgr->Cancel(winfo->rotation_timer);
-		winfo->rotation_timer = 0;
+		winfo->rotation_timer = nullptr;
 		}
 
 	double rotation_interval = winfo->interval;
@@ -1454,7 +1454,7 @@ void Manager::InstallRotationTimer(WriterInfo* winfo)
 				winfo->open_time = network_time;
 
 			const char* base_time = log_rotate_base_time ?
-				log_rotate_base_time->AsString()->CheckString() : 0;
+				log_rotate_base_time->AsString()->CheckString() : nullptr;
 
 			double base = parse_rotate_base_time(base_time);
 			double delta_t =
diff --git a/src/logging/Manager.h b/src/logging/Manager.h
index 4d062c6a07..55dc5b68c0 100644
--- a/src/logging/Manager.h
+++ b/src/logging/Manager.h
@@ -261,7 +261,7 @@ private:
 	threading::Value** RecordToFilterVals(Stream* stream, Filter* filter,
 				    RecordVal* columns);
 
-	threading::Value* ValToLogVal(Val* val, BroType* ty = 0);
+	threading::Value* ValToLogVal(Val* val, BroType* ty = nullptr);
 	Stream* FindStream(EnumVal* id);
 	void RemoveDisabledWriters(Stream* stream);
 	void InstallRotationTimer(WriterInfo* winfo);
diff --git a/src/logging/WriterBackend.cc b/src/logging/WriterBackend.cc
index 4512234734..b3bbe8b13e 100644
--- a/src/logging/WriterBackend.cc
+++ b/src/logging/WriterBackend.cc
@@ -121,7 +121,7 @@ bool WriterBackend::WriterInfo::FromBroker(broker::data d)
 WriterBackend::WriterBackend(WriterFrontend* arg_frontend) : MsgThread()
 	{
 	num_fields = 0;
-	fields = 0;
+	fields = nullptr;
 	buffering = true;
 	frontend = arg_frontend;
 	info = new WriterInfo(frontend->Info());
@@ -168,7 +168,7 @@ bool WriterBackend::FinishedRotation(const char* new_name, const char* old_name,
 bool WriterBackend::FinishedRotation()
 	{
 	--rotation_counter;
-	SendOut(new RotationFinishedMessage(frontend, 0, 0, 0, 0, false, false));
+	SendOut(new RotationFinishedMessage(frontend, nullptr, nullptr, 0, 0, false, false));
 	return true;
 	}
 
diff --git a/src/logging/WriterBackend.h b/src/logging/WriterBackend.h
index bb0941322d..805b4f8b9a 100644
--- a/src/logging/WriterBackend.h
+++ b/src/logging/WriterBackend.h
@@ -82,14 +82,14 @@ public:
 		 */
 		config_map config;
 
-		WriterInfo() : path(0), rotation_interval(0.0), rotation_base(0.0),
+		WriterInfo() : path(nullptr), rotation_interval(0.0), rotation_base(0.0),
 		               network_time(0.0)
 			{
 			}
 
 		WriterInfo(const WriterInfo& other)
 			{
-			path = other.path ? copy_string(other.path) : 0;
+			path = other.path ? copy_string(other.path) : nullptr;
 			rotation_interval = other.rotation_interval;
 			rotation_base = other.rotation_base;
 			network_time = other.network_time;
diff --git a/src/logging/WriterFrontend.cc b/src/logging/WriterFrontend.cc
index f8ce418482..c8953b817e 100644
--- a/src/logging/WriterFrontend.cc
+++ b/src/logging/WriterFrontend.cc
@@ -109,12 +109,12 @@ WriterFrontend::WriterFrontend(const WriterBackend::WriterInfo& arg_info, EnumVa
 	buf = true;
 	local = arg_local;
 	remote = arg_remote;
-	write_buffer = 0;
+	write_buffer = nullptr;
 	write_buffer_pos = 0;
 	info = new WriterBackend::WriterInfo(arg_info);
 
 	num_fields = 0;
-	fields = 0;
+	fields = nullptr;
 
 	const char* w = arg_writer->Type()->AsEnumType()->Lookup(arg_writer->InternalInt());
 	name = copy_string(fmt("%s/%s", arg_info.path, w));
@@ -128,7 +128,7 @@ WriterFrontend::WriterFrontend(const WriterBackend::WriterInfo& arg_info, EnumVa
 		}
 
 	else
-		backend = 0;
+		backend = nullptr;
 	}
 
 WriterFrontend::~WriterFrontend()
@@ -152,7 +152,7 @@ void WriterFrontend::Stop()
 	if ( backend )
 		{
 		backend->SignalStop();
-		backend = 0; // Thread manager will clean it up once it finishes.
+		backend = nullptr; // Thread manager will clean it up once it finishes.
 		}
 	}
 
@@ -245,7 +245,7 @@ void WriterFrontend::FlushWriteBuffer()
 		backend->SendIn(new WriteMessage(backend, num_fields, write_buffer_pos, write_buffer));
 
 	// Clear buffer (no delete, we pass ownership to child thread.)
-	write_buffer = 0;
+	write_buffer = nullptr;
 	write_buffer_pos = 0;
 	}
 
@@ -286,7 +286,7 @@ void WriterFrontend::Rotate(const char* rotated_path, double open, double close,
 		backend->SendIn(new RotateMessage(backend, this, rotated_path, open, close, terminating));
 	else
 		// Still signal log manager that we're done.
-		log_mgr->FinishedRotation(this, 0, 0, 0, 0, false, terminating);
+		log_mgr->FinishedRotation(this, nullptr, nullptr, 0, 0, false, terminating);
 	}
 
 void WriterFrontend::DeleteVals(int num_fields, Value** vals)
diff --git a/src/logging/writers/ascii/Ascii.cc b/src/logging/writers/ascii/Ascii.cc
index f598cdc216..71c47042ba 100644
--- a/src/logging/writers/ascii/Ascii.cc
+++ b/src/logging/writers/ascii/Ascii.cc
@@ -24,7 +24,7 @@ Ascii::Ascii(WriterFrontend* frontend) : WriterBackend(frontend)
 	tsv = false;
 	use_json = false;
 	enable_utf_8 = false;
-	formatter = 0;
+	formatter = nullptr;
 	gzip_level = 0;
 	gzfile = nullptr;
 
@@ -179,7 +179,7 @@ bool Ascii::InitFilterOptions()
 bool Ascii::InitFormatter()
 	{
 	delete formatter;
-	formatter = 0;
+	formatter = nullptr;
 
 	if ( use_json )
 		{
diff --git a/src/main.cc b/src/main.cc
index acb0beb6e7..b44543173a 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -84,44 +84,44 @@ int perftools_profile = 0;
 
 DNS_Mgr* dns_mgr;
 TimerMgr* timer_mgr;
-ValManager* val_mgr = 0;
-logging::Manager* log_mgr = 0;
-threading::Manager* thread_mgr = 0;
-input::Manager* input_mgr = 0;
-plugin::Manager* plugin_mgr = 0;
-analyzer::Manager* analyzer_mgr = 0;
-file_analysis::Manager* file_mgr = 0;
-zeekygen::Manager* zeekygen_mgr = 0;
-iosource::Manager* iosource_mgr = 0;
-bro_broker::Manager* broker_mgr = 0;
-zeek::Supervisor* zeek::supervisor_mgr = 0;
-trigger::Manager* trigger_mgr = 0;
+ValManager* val_mgr = nullptr;
+logging::Manager* log_mgr = nullptr;
+threading::Manager* thread_mgr = nullptr;
+input::Manager* input_mgr = nullptr;
+plugin::Manager* plugin_mgr = nullptr;
+analyzer::Manager* analyzer_mgr = nullptr;
+file_analysis::Manager* file_mgr = nullptr;
+zeekygen::Manager* zeekygen_mgr = nullptr;
+iosource::Manager* iosource_mgr = nullptr;
+bro_broker::Manager* broker_mgr = nullptr;
+zeek::Supervisor* zeek::supervisor_mgr = nullptr;
+trigger::Manager* trigger_mgr = nullptr;
 
 std::vector<std::string> zeek_script_prefixes;
 Stmt* stmts;
-EventHandlerPtr net_done = 0;
-RuleMatcher* rule_matcher = 0;
-EventRegistry* event_registry = 0;
-ProfileLogger* profiling_logger = 0;
-ProfileLogger* segment_logger = 0;
-SampleLogger* sample_logger = 0;
+EventHandlerPtr net_done = nullptr;
+RuleMatcher* rule_matcher = nullptr;
+EventRegistry* event_registry = nullptr;
+ProfileLogger* profiling_logger = nullptr;
+ProfileLogger* segment_logger = nullptr;
+SampleLogger* sample_logger = nullptr;
 int signal_val = 0;
 extern char version[];
-const char* command_line_policy = 0;
+const char* command_line_policy = nullptr;
 vector<string> params;
 set<string> requested_plugins;
-const char* proc_status_file = 0;
+const char* proc_status_file = nullptr;
 
-OpaqueType* md5_type = 0;
-OpaqueType* sha1_type = 0;
-OpaqueType* sha256_type = 0;
-OpaqueType* entropy_type = 0;
-OpaqueType* cardinality_type = 0;
-OpaqueType* topk_type = 0;
-OpaqueType* bloomfilter_type = 0;
-OpaqueType* x509_opaque_type = 0;
-OpaqueType* ocsp_resp_opaque_type = 0;
-OpaqueType* paraglob_type = 0;
+OpaqueType* md5_type = nullptr;
+OpaqueType* sha1_type = nullptr;
+OpaqueType* sha256_type = nullptr;
+OpaqueType* entropy_type = nullptr;
+OpaqueType* cardinality_type = nullptr;
+OpaqueType* topk_type = nullptr;
+OpaqueType* bloomfilter_type = nullptr;
+OpaqueType* x509_opaque_type = nullptr;
+OpaqueType* ocsp_resp_opaque_type = nullptr;
+OpaqueType* paraglob_type = nullptr;
 
 // Keep copy of command line
 int bro_argc;
@@ -130,7 +130,7 @@ char** bro_argv;
 const char* zeek_version()
 	{
 #ifdef DEBUG
-	static char* debug_version = 0;
+	static char* debug_version = nullptr;
 
 	if ( ! debug_version )
 		{
@@ -311,7 +311,7 @@ void terminate_bro()
 	// free the global scope
 	pop_scope();
 
-	reporter = 0;
+	reporter = nullptr;
 	}
 
 void zeek_terminate_loop(const char* reason)
@@ -527,8 +527,8 @@ int main(int argc, char** argv)
 	if ( options.random_seed_input_file )
 		seed_load_file = options.random_seed_input_file->data();
 
-	init_random_seed((seed_load_file && *seed_load_file ? seed_load_file : 0),
-					 options.random_seed_output_file ? options.random_seed_output_file->data() : 0);
+	init_random_seed((seed_load_file && *seed_load_file ? seed_load_file : nullptr),
+					 options.random_seed_output_file ? options.random_seed_output_file->data() : nullptr);
 	// DEBUG_MSG("HMAC key: %s\n", md5_digest_print(shared_hmac_md5_key));
 	init_hash_function();
 
@@ -748,7 +748,7 @@ int main(int argc, char** argv)
 
 	if ( g_policy_debug )
 		// ### Add support for debug command file.
-		dbg_init_debugger(0);
+		dbg_init_debugger(nullptr);
 
 	if ( ! options.pcap_file && ! options.interface )
 		{
@@ -847,7 +847,7 @@ int main(int argc, char** argv)
 	if ( stmts )
 		{
 		stmt_flow_type flow;
-		Frame f(current_scope()->Length(), 0, 0);
+		Frame f(current_scope()->Length(), nullptr, nullptr);
 		g_frame_stack.push_back(&f);
 
 		try
diff --git a/src/plugin/ComponentManager.h b/src/plugin/ComponentManager.h
index 87d22fc189..c58db68765 100644
--- a/src/plugin/ComponentManager.h
+++ b/src/plugin/ComponentManager.h
@@ -134,7 +134,7 @@ ComponentManager<T, C>::ComponentManager(const string& arg_module, const string&
 	  tag_enum_type(make_intrusive<EnumType>(module + "::" + local_id))
 	{
 	auto id = install_ID(local_id.c_str(), module.c_str(), true, true);
-	add_type(id.get(), tag_enum_type, 0);
+	add_type(id.get(), tag_enum_type, nullptr);
 	zeekygen_mgr->Identifier(std::move(id));
 	}
 
diff --git a/src/plugin/Manager.cc b/src/plugin/Manager.cc
index 60be0212d7..09275e639f 100644
--- a/src/plugin/Manager.cc
+++ b/src/plugin/Manager.cc
@@ -19,9 +19,9 @@
 
 using namespace plugin;
 
-Plugin* Manager::current_plugin = 0;
-const char* Manager::current_dir = 0;
-const char* Manager::current_sopath = 0;
+Plugin* Manager::current_plugin = nullptr;
+const char* Manager::current_dir = nullptr;
+const char* Manager::current_sopath = nullptr;
 
 Manager::Manager()
 	{
@@ -29,7 +29,7 @@ Manager::Manager()
 	hooks = new hook_list*[NUM_HOOKS];
 
 	for ( int i = 0; i < NUM_HOOKS; i++ )
-		hooks[i] = 0;
+		hooks[i] = nullptr;
 	}
 
 Manager::~Manager()
@@ -238,7 +238,7 @@ bool Manager::ActivateDynamicPluginInternal(const std::string& name, bool ok_if_
 			{
 			const char* path = gl.gl_pathv[i];
 
-			current_plugin = 0;
+			current_plugin = nullptr;
 			current_dir = dir.c_str();
 			current_sopath = path;
 			void* hdl = dlopen(path, RTLD_LAZY | RTLD_GLOBAL);
@@ -270,9 +270,9 @@ bool Manager::ActivateDynamicPluginInternal(const std::string& name, bool ok_if_
 				reporter->FatalError("inconsistent plugin name: %s vs %s",
 						     current_plugin->Name().c_str(), name.c_str());
 
-			current_dir = 0;
-			current_sopath = 0;
-			current_plugin = 0;
+			current_dir = nullptr;
+			current_sopath = nullptr;
+			current_plugin = nullptr;
 
 			DBG_LOG(DBG_PLUGINS, "  Loaded %s", path);
 			}
@@ -461,7 +461,7 @@ Manager::inactive_plugin_list Manager::InactivePlugins() const
 
 Manager::plugin_list* Manager::ActivePluginsInternal()
 	{
-	static plugin_list* plugins = 0;
+	static plugin_list* plugins = nullptr;
 
 	if ( ! plugins )
 		plugins = new plugin_list;
@@ -471,7 +471,7 @@ Manager::plugin_list* Manager::ActivePluginsInternal()
 
 Manager::bif_init_func_map* Manager::BifFilesInternal()
 	{
-	static bif_init_func_map* bifs = 0;
+	static bif_init_func_map* bifs = nullptr;
 
 	if ( ! bifs )
 		bifs = new bif_init_func_map;
@@ -571,7 +571,7 @@ void Manager::DisableHook(HookType hook, Plugin* plugin)
 	if ( l->empty() )
 		{
 		delete l;
-		hooks[hook] = 0;
+		hooks[hook] = nullptr;
 		}
 	}
 
diff --git a/src/plugin/Manager.h b/src/plugin/Manager.h
index 25c0235ebf..9c0ffecad5 100644
--- a/src/plugin/Manager.h
+++ b/src/plugin/Manager.h
@@ -168,7 +168,7 @@ public:
 	bool HavePluginForHook(HookType hook) const
 		{
 		// Inline to avoid the function call.
-		return hooks[hook] != 0;
+		return hooks[hook] != nullptr;
 		}
 
 	/**
diff --git a/src/plugin/Plugin.cc b/src/plugin/Plugin.cc
index 29f177d329..5538b87b28 100644
--- a/src/plugin/Plugin.cc
+++ b/src/plugin/Plugin.cc
@@ -475,7 +475,7 @@ void Plugin::Describe(ODesc* d) const
 
 	for ( bif_item_list::const_iterator i = items.begin(); i != items.end(); i++ )
 		{
-		const char* type = 0;
+		const char* type = nullptr;
 
 		switch ( (*i).GetType() ) {
 		case BifItem::FUNCTION:
diff --git a/src/probabilistic/BloomFilter.cc b/src/probabilistic/BloomFilter.cc
index 71996dc6c8..e9289a9db9 100644
--- a/src/probabilistic/BloomFilter.cc
+++ b/src/probabilistic/BloomFilter.cc
@@ -17,7 +17,7 @@ using namespace probabilistic;
 
 BloomFilter::BloomFilter()
 	{
-	hasher = 0;
+	hasher = nullptr;
 	}
 
 BloomFilter::BloomFilter(const Hasher* arg_hasher)
@@ -142,7 +142,7 @@ std::string BasicBloomFilter::InternalState() const
 
 BasicBloomFilter::BasicBloomFilter()
 	{
-	bits = 0;
+	bits = nullptr;
 	}
 
 BasicBloomFilter::BasicBloomFilter(const Hasher* hasher, size_t cells)
@@ -195,7 +195,7 @@ bool BasicBloomFilter::DoUnserialize(const broker::data& data)
 
 CountingBloomFilter::CountingBloomFilter()
 	{
-	cells = 0;
+	cells = nullptr;
 	}
 
 CountingBloomFilter::CountingBloomFilter(const Hasher* hasher,
diff --git a/src/probabilistic/Topk.cc b/src/probabilistic/Topk.cc
index de3643a65d..fff53cbc1b 100644
--- a/src/probabilistic/Topk.cc
+++ b/src/probabilistic/Topk.cc
@@ -44,10 +44,10 @@ TopkVal::TopkVal(uint64_t arg_size) : OpaqueVal(topk_type)
 	elementDict = new PDict<Element>;
 	elementDict->SetDeleteFunc(topk_element_hash_delete_func);
 	size = arg_size;
-	type = 0;
+	type = nullptr;
 	numElements = 0;
 	pruned = false;
-	hash = 0;
+	hash = nullptr;
 	}
 
 TopkVal::TopkVal() : OpaqueVal(topk_type)
@@ -55,9 +55,9 @@ TopkVal::TopkVal() : OpaqueVal(topk_type)
 	elementDict = new PDict<Element>;
 	elementDict->SetDeleteFunc(topk_element_hash_delete_func);
 	size = 0;
-	type = 0;
+	type = nullptr;
 	numElements = 0;
-	hash = 0;
+	hash = nullptr;
 	}
 
 TopkVal::~TopkVal()
@@ -86,7 +86,7 @@ void TopkVal::Merge(const TopkVal* value, bool doPrune)
 		return;
 		}
 
-	if ( type == 0 )
+	if ( type == nullptr )
 		{
 		assert(numElements == 0);
 		Typify(value->type);
@@ -115,7 +115,7 @@ void TopkVal::Merge(const TopkVal* value, bool doPrune)
 			HashKey* key = GetHash(e->value);
 			Element* olde = (Element*) elementDict->Lookup(key);
 
-			if ( olde == 0 )
+			if ( olde == nullptr )
 				{
 				olde = new Element();
 				olde->epsilon = 0;
@@ -196,7 +196,7 @@ VectorVal* TopkVal::GetTopK(int k) const // returns vector
 	if ( numElements == 0 )
 		{
 		reporter->Error("Cannot return topk of empty");
-		return 0;
+		return nullptr;
 		}
 
 	auto vector_index = make_intrusive<TypeList>(IntrusivePtr{NewRef{}, type});
@@ -238,7 +238,7 @@ uint64_t TopkVal::GetCount(Val* value) const
 	Element* e = (Element*) elementDict->Lookup(key);
 	delete key;
 
-	if ( e == 0 )
+	if ( e == nullptr )
 		{
 		reporter->Error("GetCount for element that is not in top-k");
 		return 0;
@@ -253,7 +253,7 @@ uint64_t TopkVal::GetEpsilon(Val* value) const
 	Element* e = (Element*) elementDict->Lookup(key);
 	delete key;
 
-	if ( e == 0 )
+	if ( e == nullptr )
 		{
 		reporter->Error("GetEpsilon for element that is not in top-k");
 		return 0;
@@ -297,7 +297,7 @@ void TopkVal::Encountered(Val* encountered)
 	HashKey* key = GetHash(encountered);
 	Element* e = (Element*) elementDict->Lookup(key);
 
-	if ( e == 0 )
+	if ( e == nullptr )
 		{
 		e = new Element();
 		e->epsilon = 0;
@@ -370,7 +370,7 @@ void TopkVal::IncrementCounter(Element* e, unsigned int count)
 	// well, let's test if there is a bucket for currcount++
 	std::list<Bucket*>::iterator bucketIter = currBucket->bucketPos;
 
-	Bucket* nextBucket = 0;
+	Bucket* nextBucket = nullptr;
 
 	bucketIter++;
 
@@ -380,7 +380,7 @@ void TopkVal::IncrementCounter(Element* e, unsigned int count)
 	if ( bucketIter != buckets.end() && (*bucketIter)->count == currcount+count )
 		nextBucket = *bucketIter;
 
-	if ( nextBucket == 0 )
+	if ( nextBucket == nullptr )
 		{
 		// the bucket for the value that we want does not exist.
 		// create it...
@@ -405,7 +405,7 @@ void TopkVal::IncrementCounter(Element* e, unsigned int count)
 		{
 		buckets.remove(currBucket);
 		delete currBucket;
-		currBucket = 0;
+		currBucket = nullptr;
 		}
 	}
 
@@ -519,7 +519,7 @@ bool TopkVal::DoUnserialize(const broker::data& data)
 			b->elements.insert(b->elements.end(), e);
 
 			HashKey* key = GetHash(e->value);
-			assert (elementDict->Lookup(key) == 0);
+			assert (elementDict->Lookup(key) == nullptr);
 
 			elementDict->Insert(key, e);
 			delete key;
diff --git a/src/threading/BasicThread.cc b/src/threading/BasicThread.cc
index 3374380748..c447051bab 100644
--- a/src/threading/BasicThread.cc
+++ b/src/threading/BasicThread.cc
@@ -22,7 +22,7 @@ BasicThread::BasicThread()
 	buf_len = STD_FMT_BUF_LEN;
 	buf = (char*) safe_malloc(buf_len);
 
-	strerr_buffer = 0;
+	strerr_buffer = nullptr;
 
 	name = copy_string(fmt("thread-%" PRIu64, ++thread_counter));
 
@@ -191,5 +191,5 @@ void* BasicThread::launcher(void *arg)
 
 	thread->Done();
 
-	return 0;
+	return nullptr;
 	}
diff --git a/src/threading/MsgThread.cc b/src/threading/MsgThread.cc
index f662d0a46c..2b6ef01ead 100644
--- a/src/threading/MsgThread.cc
+++ b/src/threading/MsgThread.cc
@@ -172,7 +172,7 @@ bool ReporterMessage::Process()
 	return true;
 	}
 
-MsgThread::MsgThread() : BasicThread(), queue_in(this, 0), queue_out(0, this)
+MsgThread::MsgThread() : BasicThread(), queue_in(this, nullptr), queue_out(nullptr, this)
 	{
 	cnt_sent_in = cnt_sent_out = 0;
 	main_finished = false;
@@ -367,7 +367,7 @@ BasicOutputMessage* MsgThread::RetrieveOut()
 	{
 	BasicOutputMessage* msg = queue_out.Get();
 	if ( ! msg )
-		return 0;
+		return nullptr;
 
 	DBG_LOG(DBG_THREADING, "Retrieved '%s' from %s",  msg->Name(), Name());
 
@@ -379,7 +379,7 @@ BasicInputMessage* MsgThread::RetrieveIn()
 	BasicInputMessage* msg = queue_in.Get();
 
 	if ( ! msg )
-		return 0;
+		return nullptr;
 
 #ifdef DEBUG
 	string s = Fmt("Retrieved '%s' in %s",  msg->Name(), Name());
diff --git a/src/threading/SerialTypes.cc b/src/threading/SerialTypes.cc
index bd85b846f9..b04549f0b6 100644
--- a/src/threading/SerialTypes.cc
+++ b/src/threading/SerialTypes.cc
@@ -26,7 +26,7 @@ bool Field::Read(SerializationFormat* fmt)
 		secondary_name = copy_string(tmp_secondary_name.c_str());
 		}
 	else
-		secondary_name = 0;
+		secondary_name = nullptr;
 
 	bool success = (fmt->Read(&tmp_name, "name")
 			&& fmt->Read(&t, "type")
diff --git a/src/threading/SerialTypes.h b/src/threading/SerialTypes.h
index dbd3635b94..628c3b40f7 100644
--- a/src/threading/SerialTypes.h
+++ b/src/threading/SerialTypes.h
@@ -31,16 +31,16 @@ struct Field {
 	 * Constructor.
 	 */
 	Field(const char* name, const char* secondary_name, TypeTag type, TypeTag subtype, bool optional)
-		: name(name ? copy_string(name) : 0),
-		  secondary_name(secondary_name ? copy_string(secondary_name) : 0),
+		: name(name ? copy_string(name) : nullptr),
+		  secondary_name(secondary_name ? copy_string(secondary_name) : nullptr),
 		  type(type), subtype(subtype), optional(optional)	{ }
 
 	/**
 	 * Copy constructor.
 	 */
 	Field(const Field& other)
-		: name(other.name ? copy_string(other.name) : 0),
-		  secondary_name(other.secondary_name ? copy_string(other.secondary_name) : 0),
+		: name(other.name ? copy_string(other.name) : nullptr),
+		  secondary_name(other.secondary_name ? copy_string(other.secondary_name) : nullptr),
 		  type(other.type), subtype(other.subtype), optional(other.optional)	{ }
 
 	~Field()
diff --git a/src/threading/formatters/Ascii.cc b/src/threading/formatters/Ascii.cc
index ce8d5461f6..a5337dac1e 100644
--- a/src/threading/formatters/Ascii.cc
+++ b/src/threading/formatters/Ascii.cc
@@ -214,7 +214,7 @@ threading::Value* Ascii::ParseValue(const string& s, const string& name, TypeTag
 
 	threading::Value* val = new threading::Value(type, subtype, true);
 	const char* start = s.c_str();
-	char* end = 0;
+	char* end = nullptr;
 	errno = 0;
 	size_t pos;
 
@@ -411,7 +411,7 @@ threading::Value* Ascii::ParseValue(const string& s, const string& name, TypeTag
 				}
 
 			threading::Value* newval = ParseValue(element, name, subtype);
-			if ( newval == 0 )
+			if ( newval == nullptr )
 				{
 				GetThread()->Warning("Error while reading set or vector");
 				error = true;
@@ -429,7 +429,7 @@ threading::Value* Ascii::ParseValue(const string& s, const string& name, TypeTag
 		if ( ! error && (s.empty() || *s.rbegin() == separators.set_separator[0]) )
 			{
 			lvals[pos] = ParseValue("", name, subtype);
-			if ( lvals[pos] == 0 )
+			if ( lvals[pos] == nullptr )
 				{
 				GetThread()->Warning("Error while trying to add empty set element");
 				goto parse_error;
@@ -470,7 +470,7 @@ threading::Value* Ascii::ParseValue(const string& s, const string& name, TypeTag
 
 parse_error:
 	delete val;
-	return 0;
+	return nullptr;
 	}
 
 bool Ascii::CheckNumberError(const char* start, const char* end) const
diff --git a/src/util.cc b/src/util.cc
index e75e79882d..0b1128b296 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -277,7 +277,7 @@ std::string get_escaped_string(const char* str, size_t len, bool escape_all)
 char* copy_string(const char* s)
 	{
 	if ( ! s )
-		return 0;
+		return nullptr;
 
 	char* c = new char[strlen(s)+1];
 	strcpy(c, s);
@@ -558,7 +558,7 @@ const char* strpbrk_n(size_t len, const char* s, const char* charset)
 		if ( strchr(charset, *p) )
 			return p;
 
-	return 0;
+	return nullptr;
 	}
 
 #ifndef HAVE_STRCASESTR
@@ -819,7 +819,7 @@ const char* fmt_bytes(const char* data, int len)
 
 const char* vfmt(const char* format, va_list al)
 	{
-	static char* buf = 0;
+	static char* buf = nullptr;
 	static unsigned int buf_len = 1024;
 
 	if ( ! buf )
@@ -1017,7 +1017,7 @@ void hmac_md5(size_t size, const unsigned char* bytes, unsigned char digest[16])
 static bool read_random_seeds(const char* read_file, uint32_t* seed,
 				uint32_t* buf, int bufsiz)
 	{
-	FILE* f = 0;
+	FILE* f = nullptr;
 
 	if ( ! (f = fopen(read_file, "r")) )
 		{
@@ -1053,7 +1053,7 @@ static bool read_random_seeds(const char* read_file, uint32_t* seed,
 static bool write_random_seeds(const char* write_file, uint32_t seed,
 				uint32_t* buf, int bufsiz)
 	{
-	FILE* f = 0;
+	FILE* f = nullptr;
 
 	if ( ! (f = fopen(write_file, "w+")) )
 		{
@@ -1345,7 +1345,7 @@ bool is_package_loader(const string& path)
 FILE* open_file(const string& path, const string& mode)
 	{
 	if ( path.empty() )
-		return 0;
+		return nullptr;
 
 	FILE* rval = fopen(path.c_str(), mode.c_str());
 
@@ -1384,7 +1384,7 @@ FILE* open_package(string& path, const string& mode)
 	string package_loader = "__load__" + script_extensions[0];
 	reporter->Error("Failed to open package '%s': missing '%s' file",
 	                arg_path.c_str(), package_loader.c_str());
-	return 0;
+	return nullptr;
 	}
 
 TEST_CASE("util path ops")
@@ -1810,7 +1810,7 @@ FILE* rotate_file(const char* name, RecordVal* rotate_info)
 	if ( ! newf )
 		{
 		reporter->Error("rotate_file: can't open %s: %s", tmpname, strerror(errno));
-		return 0;
+		return nullptr;
 		}
 
 	// Then move old file to "<name>.<pid>.<timestamp>" and make sure
@@ -1822,7 +1822,7 @@ FILE* rotate_file(const char* name, RecordVal* rotate_info)
 		fclose(newf);
 		unlink(newname);
 		unlink(tmpname);
-		return 0;
+		return nullptr;
 		}
 
 	// Close current file, and move the tmp to its place.
diff --git a/src/util.h b/src/util.h
index c212d5d8da..66d65ba622 100644
--- a/src/util.h
+++ b/src/util.h
@@ -139,7 +139,7 @@ inline std::string get_escaped_string(const std::string& str, bool escape_all)
 
 std::vector<std::string>* tokenize_string(std::string_view input,
 					  std::string_view delim,
-					  std::vector<std::string>* rval = 0, int limit = 0);
+					  std::vector<std::string>* rval = nullptr, int limit = 0);
 
 std::vector<std::string_view> tokenize_string(std::string_view input, const char delim) noexcept;
 
@@ -167,7 +167,7 @@ extern char* strcasestr(const char* s, const char* find);
 #endif
 extern const char* strpbrk_n(size_t len, const char* s, const char* charset);
 template<class T> int atoi_n(int len, const char* s, const char** end, int base, T& result);
-extern char* uitoa_n(uint64_t value, char* str, int n, int base, const char* prefix=0);
+extern char* uitoa_n(uint64_t value, char* str, int n, int base, const char* prefix=nullptr);
 int strstr_n(const int big_len, const unsigned char* big,
 		const int little_len, const unsigned char* little);
 extern int fputs(int len, const char* s, FILE* fp);
diff --git a/src/zeekygen/IdentifierInfo.h b/src/zeekygen/IdentifierInfo.h
index 949a503664..e21912d8fb 100644
--- a/src/zeekygen/IdentifierInfo.h
+++ b/src/zeekygen/IdentifierInfo.h
@@ -91,7 +91,7 @@ public:
 	 * comments are correctly associated.
 	 */
 	void CompletedTypeDecl()
-		{ last_field_seen = 0; }
+		{ last_field_seen = nullptr; }
 
 	/**
 	 * @return the script-level ID tracked by this info object.
diff --git a/src/zeekygen/Manager.cc b/src/zeekygen/Manager.cc
index b61cb15404..6636447516 100644
--- a/src/zeekygen/Manager.cc
+++ b/src/zeekygen/Manager.cc
@@ -288,7 +288,7 @@ void Manager::Identifier(IntrusivePtr<ID> id)
 			{
 			DBG_LOG(DBG_ZEEKYGEN, "Finished document for type %s", id->Name());
 			incomplete_type->CompletedTypeDecl();
-			incomplete_type = 0;
+			incomplete_type = nullptr;
 			return;
 			}
 
@@ -318,7 +318,7 @@ void Manager::Identifier(IntrusivePtr<ID> id)
 		// Handled specially since they don't have a script location.
 		DBG_LOG(DBG_ZEEKYGEN, "Made internal IdentifierInfo %s",
 		        id->Name());
-		CreateIdentifierInfo(id, 0);
+		CreateIdentifierInfo(id, nullptr);
 		return;
 		}
 
diff --git a/src/zeekygen/Target.cc b/src/zeekygen/Target.cc
index 34c3df6c9f..9aae9b82fe 100644
--- a/src/zeekygen/Target.cc
+++ b/src/zeekygen/Target.cc
@@ -438,7 +438,7 @@ vector<string> dir_contents_recursive(string dir)
 	char* dir_copy = copy_string(dir.c_str());
 	char** scan_path = new char*[2];
 	scan_path[0] = dir_copy;
-	scan_path[1] = 0;
+	scan_path[1] = NULL;
 
 	FTS* fts = fts_open(scan_path, FTS_NOCHDIR, 0);
 
diff --git a/src/zeekygen/Target.h b/src/zeekygen/Target.h
index 9aa95e58cf..2b8ae22c6d 100644
--- a/src/zeekygen/Target.h
+++ b/src/zeekygen/Target.h
@@ -148,7 +148,7 @@ public:
 		target_creator_map::const_iterator it = target_creators.find(type_name);
 
 		if ( it == target_creators.end() )
-			return 0;
+			return nullptr;
 
 		return it->second(name, pattern);
 		}