diff --git a/CHANGES b/CHANGES
index bd27000d15..334df3c7dd 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,4 +1,24 @@
 
+3.2.0-dev.167 | 2020-02-27 14:24:55 -0800
+
+  * Expr: use fmt instead of sprintf (Tim Wojtulewicz, Corelight)
+
+  * Expr: other minor initialization cleanup (Tim Wojtulewicz, Corelight)
+
+  * Expr: use List::empty() (Tim Wojtulewicz, Corelight)
+
+  * Expr: Convert a bunch of methods returning ints to return bools (Tim Wojtulewicz, Corelight)
+
+  * IPAddr: minor cleanup (Tim Wojtulewicz, Corelight)
+
+    - Mark empty constructors/destructors as default
+    - Initialization cleanup
+    - Remove unnecessary elses from before returns
+
+  * PriorityQueue: initialization cleanup (Tim Wojtulewicz, Corelight)
+
+  * IP: Cleanup initialization, make a few functions consistent (Tim Wojtulewicz, Corelight)
+
 3.2.0-dev.159 | 2020-02-26 19:51:24 -0800
 
   * Pop global frame stack on exception. (Johanna Amann, Corelight)
diff --git a/VERSION b/VERSION
index a1cb4ac2a1..a55db9a55f 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-3.2.0-dev.159
+3.2.0-dev.167
diff --git a/src/Expr.cc b/src/Expr.cc
index b1f43c5536..83ad450835 100644
--- a/src/Expr.cc
+++ b/src/Expr.cc
@@ -55,12 +55,8 @@ const char* expr_name(BroExprTag t)
 	return expr_names[int(t)];
 	}
 
-Expr::Expr(BroExprTag arg_tag)
+Expr::Expr(BroExprTag arg_tag) : tag(arg_tag), type(0), paren(false)
 	{
-	tag = arg_tag;
-	type = 0;
-	paren = 0;
-
 	SetLocationInfo(&start_location, &end_location);
 	}
 
@@ -69,14 +65,14 @@ Expr::~Expr()
 	Unref(type);
 	}
 
-int Expr::CanAdd() const
+bool Expr::CanAdd() const
 	{
-	return 0;
+	return false;
 	}
 
-int Expr::CanDel() const
+bool Expr::CanDel() const
 	{
-	return 0;
+	return false;
 	}
 
 void Expr::Add(Frame* /* f */)
@@ -113,14 +109,14 @@ BroType* Expr::InitType() const
 	return type->Ref();
 	}
 
-int Expr::IsRecordElement(TypeDecl* /* td */) const
+bool Expr::IsRecordElement(TypeDecl* /* td */) const
 	{
-	return 0;
+	return false;
 	}
 
-int Expr::IsPure() const
+bool Expr::IsPure() const
 	{
-	return 1;
+	return true;
 	}
 
 Val* Expr::InitVal(const BroType* t, Val* aggr) const
@@ -137,7 +133,7 @@ Val* Expr::InitVal(const BroType* t, Val* aggr) const
 	return check_and_promote(Eval(0), t, 1);
 	}
 
-int Expr::IsError() const
+bool Expr::IsError() const
 	{
 	return type && type->Tag() == TYPE_ERROR;
 	}
@@ -153,12 +149,12 @@ void Expr::SetError(const char* msg)
 	SetError();
 	}
 
-int Expr::IsZero() const
+bool Expr::IsZero() const
 	{
 	return IsConst() && ExprVal()->IsZero();
 	}
 
-int Expr::IsOne() const
+bool Expr::IsOne() const
 	{
 	return IsConst() && ExprVal()->IsOne();
 	}
@@ -295,7 +291,7 @@ void NameExpr::Assign(Frame* f, Val* v)
 		f->SetElement(id, v);
 	}
 
-int NameExpr::IsPure() const
+bool NameExpr::IsPure() const
 	{
 	return id->IsConst();
 	}
@@ -414,7 +410,7 @@ Val* UnaryExpr::Eval(Frame* f) const
 		}
 	}
 
-int UnaryExpr::IsPure() const
+bool UnaryExpr::IsPure() const
 	{
 	return op->IsPure();
 	}
@@ -551,7 +547,7 @@ Val* BinaryExpr::Eval(Frame* f) const
 	return result;
 	}
 
-int BinaryExpr::IsPure() const
+bool BinaryExpr::IsPure() const
 	{
 	return op1->IsPure() && op2->IsPure();
 	}
@@ -604,20 +600,20 @@ Val* BinaryExpr::Fold(Val* v1, Val* v2) const
 	bro_int_t i1 = 0, i2 = 0, i3 = 0;
 	bro_uint_t u1 = 0, u2 = 0, u3 = 0;
 	double d1 = 0.0, d2 = 0.0, d3 = 0.0;
-	int is_integral = 0;
-	int is_unsigned = 0;
+	bool is_integral = false;
+	bool is_unsigned = false;
 
 	if ( it == TYPE_INTERNAL_INT )
 		{
 		i1 = v1->InternalInt();
 		i2 = v2->InternalInt();
-		++is_integral;
+		is_integral = true;
 		}
 	else if ( it == TYPE_INTERNAL_UNSIGNED )
 		{
 		u1 = v1->InternalUnsigned();
 		u2 = v2->InternalUnsigned();
-		++is_unsigned;
+		is_unsigned = true;
 		}
 	else if ( it == TYPE_INTERNAL_DOUBLE )
 		{
@@ -858,7 +854,7 @@ Val* BinaryExpr::AddrFold(Val* v1, Val* v2) const
 	{
 	IPAddr a1 = v1->AsAddr();
 	IPAddr a2 = v2->AsAddr();
-	int result = 0;
+	bool result = false;
 
 	switch ( tag ) {
 
@@ -893,7 +889,7 @@ Val* BinaryExpr::SubNetFold(Val* v1, Val* v2) const
 	const IPPrefix& n1 = v1->AsSubNet();
 	const IPPrefix& n2 = v2->AsSubNet();
 
-	bool result = ( n1 == n2 ) ? true : false;
+	bool result = n1 == n2;
 
 	if ( tag == EXPR_NE )
 		result = ! result;
@@ -1053,9 +1049,9 @@ Val* IncrExpr::Eval(Frame* f) const
 		}
 	}
 
-int IncrExpr::IsPure() const
+bool IncrExpr::IsPure() const
 	{
-	return 0;
+	return false;
 	}
 
 ComplementExpr::ComplementExpr(Expr* arg_op) : UnaryExpr(EXPR_COMPLEMENT, arg_op)
@@ -1605,8 +1601,8 @@ Val* BoolExpr::Eval(Frame* f) const
 	if ( ! v1 )
 		return 0;
 
-	int is_vec1 = is_vector(op1);
-	int is_vec2 = is_vector(op2);
+	bool is_vec1 = is_vector(op1);
+	bool is_vec2 = is_vector(op2);
 
 	// Handle scalar op scalar
 	if ( ! is_vec1 && ! is_vec2 )
@@ -2044,7 +2040,7 @@ Val* CondExpr::Eval(Frame* f) const
 	return result;
 	}
 
-int CondExpr::IsPure() const
+bool CondExpr::IsPure() const
 	{
 	return op1->IsPure() && op2->IsPure() && op3->IsPure();
 	}
@@ -2172,7 +2168,7 @@ bool AssignExpr::TypeCheck(attr_list* attrs)
 			std::copy(attrs->begin(), attrs->end(), std::back_inserter(*attr_copy));
 			}
 
-		bool empty_list_assignment = (op2->AsListExpr()->Exprs().length() == 0);
+		bool empty_list_assignment = (op2->AsListExpr()->Exprs().empty());
 
 		if ( op1->Type()->IsSet() )
 			op2 = new SetConstructorExpr(op2->AsListExpr(), attr_copy);
@@ -2289,11 +2285,8 @@ bool AssignExpr::TypeCheckArithmetics(TypeTag bt1, TypeTag bt2)
 	{
 	if ( ! IsArithmetic(bt2) )
 		{
-		char err[512];
-		snprintf(err, sizeof(err),
-			"assignment of non-arithmetic value to arithmetic (%s/%s)",
-			 type_name(bt1), type_name(bt2));
-		ExprError(err);
+		ExprError(fmt("assignment of non-arithmetic value to arithmetic (%s/%s)",
+				type_name(bt1), type_name(bt2)));
 		return false;
 		}
 
@@ -2499,7 +2492,7 @@ Val* AssignExpr::InitVal(const BroType* t, Val* aggr) const
 		}
 	}
 
-int AssignExpr::IsRecordElement(TypeDecl* td) const
+bool AssignExpr::IsRecordElement(TypeDecl* td) const
 	{
 	if ( op1->Tag() == EXPR_NAME )
 		{
@@ -2510,15 +2503,15 @@ int AssignExpr::IsRecordElement(TypeDecl* td) const
 			td->id = copy_string(n->Id()->Name());
 			}
 
-		return 1;
+		return true;
 		}
-	else
-		return 0;
+
+	return false;
 	}
 
-int AssignExpr::IsPure() const
+bool AssignExpr::IsPure() const
 	{
-	return 0;
+	return false;
 	}
 
 IndexSliceAssignExpr::IndexSliceAssignExpr(Expr* op1, Expr* op2, int is_init)
@@ -2595,19 +2588,19 @@ IndexExpr::IndexExpr(Expr* arg_op1, ListExpr* arg_op2, bool arg_is_slice)
 
 	}
 
-int IndexExpr::CanAdd() const
+bool IndexExpr::CanAdd() const
 	{
 	if ( IsError() )
-		return 1;	// avoid cascading the error report
+		return true;	// avoid cascading the error report
 
 	// "add" only allowed if our type is "set".
 	return op1->Type()->IsSet();
 	}
 
-int IndexExpr::CanDel() const
+bool IndexExpr::CanDel() const
 	{
 	if ( IsError() )
-		return 1;	// avoid cascading the error report
+		return true;	// avoid cascading the error report
 
 	return op1->Type()->Tag() == TYPE_TABLE;
 	}
@@ -2993,7 +2986,7 @@ Expr* FieldExpr::MakeLvalue()
 	return new RefExpr(this);
 	}
 
-int FieldExpr::CanDel() const
+bool FieldExpr::CanDel() const
 	{
 	return td->FindAttr(ATTR_DEFAULT) || td->FindAttr(ATTR_OPTIONAL);
 	}
@@ -3212,7 +3205,7 @@ TableConstructorExpr::TableConstructorExpr(ListExpr* constructor_list,
 		}
 	else
 		{
-		if ( constructor_list->Exprs().length() == 0 )
+		if ( constructor_list->Exprs().empty() )
 			SetType(new TableType(new TypeList(base_type(TYPE_ANY)), 0));
 		else
 			{
@@ -3324,7 +3317,7 @@ SetConstructorExpr::SetConstructorExpr(ListExpr* constructor_list,
 		}
 	else
 		{
-		if ( constructor_list->Exprs().length() == 0 )
+		if ( constructor_list->Exprs().empty() )
 			SetType(new ::SetType(new TypeList(base_type(TYPE_ANY)), 0));
 		else
 			SetType(init_type(constructor_list));
@@ -3441,7 +3434,7 @@ VectorConstructorExpr::VectorConstructorExpr(ListExpr* constructor_list,
 		}
 	else
 		{
-		if ( constructor_list->Exprs().length() == 0 )
+		if ( constructor_list->Exprs().empty() )
 			{
 			// vector().
 			// By default, assign VOID type here. A vector with
@@ -3553,7 +3546,7 @@ void FieldAssignExpr::EvalIntoAggregate(const BroType* t, Val* aggr, Frame* f)
 		}
 	}
 
-int FieldAssignExpr::IsRecordElement(TypeDecl* td) const
+bool FieldAssignExpr::IsRecordElement(TypeDecl* td) const
 	{
 	if ( td )
 		{
@@ -3561,7 +3554,7 @@ int FieldAssignExpr::IsRecordElement(TypeDecl* td) const
 		td->id = copy_string(field_name.c_str());
 		}
 
-	return 1;
+	return true;
 	}
 
 void FieldAssignExpr::ExprDescribe(ODesc* d) const
@@ -4028,9 +4021,9 @@ ScheduleExpr::~ScheduleExpr()
 	Unref(event);
 	}
 
-int ScheduleExpr::IsPure() const
+bool ScheduleExpr::IsPure() const
 	{
-	return 0;
+	return false;
 	}
 
 Val* ScheduleExpr::Eval(Frame* f) const
@@ -4304,7 +4297,7 @@ CallExpr::~CallExpr()
 	Unref(args);
 	}
 
-int CallExpr::IsPure() const
+bool CallExpr::IsPure() const
 	{
 	if ( IsError() )
 		return 1;
@@ -4614,22 +4607,22 @@ void ListExpr::Append(Expr* e)
 	((TypeList*) type)->Append(e->Type()->Ref());
 	}
 
-int ListExpr::IsPure() const
+bool ListExpr::IsPure() const
 	{
 	for ( const auto& expr : exprs )
 		if ( ! expr->IsPure() )
-			return 0;
+			return false;
 
-	return 1;
+	return true;
 	}
 
-int ListExpr::AllConst() const
+bool ListExpr::AllConst() const
 	{
 	for ( const auto& expr : exprs )
 		if ( ! expr->IsConst() )
-			return 0;
+			return false;
 
-	return 1;
+	return true;
 	}
 
 Val* ListExpr::Eval(Frame* f) const
@@ -4654,7 +4647,7 @@ Val* ListExpr::Eval(Frame* f) const
 
 BroType* ListExpr::InitType() const
 	{
-	if ( exprs.length() == 0 )
+	if ( exprs.empty() )
 		{
 		Error("empty list in untyped initialization");
 		return 0;
@@ -5321,7 +5314,7 @@ val_list* eval_list(Frame* f, const ListExpr* l)
 		return v;
 	}
 
-int expr_greater(const Expr* e1, const Expr* e2)
+bool expr_greater(const Expr* e1, const Expr* e2)
 	{
-	return int(e1->Tag()) > int(e2->Tag());
+	return e1->Tag() > e2->Tag();
 	}
diff --git a/src/Expr.h b/src/Expr.h
index 771f4782e5..ed9049652c 100644
--- a/src/Expr.h
+++ b/src/Expr.h
@@ -16,7 +16,7 @@
 
 using std::string;
 
-typedef enum {
+enum BroExprTag : int {
 	EXPR_ANY = -1,
 	EXPR_NAME, EXPR_CONST,
 	EXPR_CLONE,
@@ -54,7 +54,7 @@ typedef enum {
 	EXPR_IS,
 	EXPR_INDEX_SLICE_ASSIGN,
 #define NUM_EXPRS (int(EXPR_INDEX_SLICE_ASSIGN) + 1)
-} BroExprTag;
+};
 
 extern const char* expr_name(BroExprTag t);
 
@@ -102,7 +102,7 @@ public:
 	// constitutes a record element, false otherwise.  If the TypeDecl*
 	// is non-nil and the expression is a record element, fills in the
 	// TypeDecl with a description of the element.
-	virtual int IsRecordElement(TypeDecl* td) const;
+	virtual bool IsRecordElement(TypeDecl* td) const;
 
 	// Returns a value corresponding to this expression interpreted
 	// as an initialization, or nil if the expression is inconsistent
@@ -112,13 +112,13 @@ public:
 	virtual Val* InitVal(const BroType* t, Val* aggr) const;
 
 	// True if the expression has no side effects, false otherwise.
-	virtual int IsPure() const;
+	virtual bool IsPure() const;
 
 	// True if the expression is a constant, false otherwise.
-	int IsConst() const	{ return tag == EXPR_CONST; }
+	bool IsConst() const	{ return tag == EXPR_CONST; }
 
 	// True if the expression is in error (to alleviate error propagation).
-	int IsError() const;
+	bool IsError() const;
 
 	// Mark expression as in error.
 	void SetError();
@@ -129,15 +129,15 @@ public:
 	inline Val* ExprVal() const;
 
 	// True if the expression is a constant zero, false otherwise.
-	int IsZero() const;
+	bool IsZero() const;
 
 	// True if the expression is a constant one, false otherwise.
-	int IsOne() const;
+	bool IsOne() const;
 
 	// True if the expression supports the "add" or "delete" operations,
 	// false otherwise.
-	virtual int CanAdd() const;
-	virtual int CanDel() const;
+	virtual bool CanAdd() const;
+	virtual bool CanDel() const;
 
 	virtual void Add(Frame* f);	// perform add operation
 	virtual void Delete(Frame* f);	// perform delete operation
@@ -149,8 +149,8 @@ public:
 
 	// Marks the expression as one requiring (or at least appearing
 	// with) parentheses.  Used for pretty-printing.
-	void MarkParen()		{ paren = 1; }
-	int IsParen() const		{ return paren; }
+	void MarkParen()		{ paren = true; }
+	bool IsParen() const		{ return paren; }
 
 	const ListExpr* AsListExpr() const
 		{
@@ -205,7 +205,7 @@ public:
 	virtual TraversalCode Traverse(TraversalCallback* cb) const = 0;
 
 protected:
-	Expr()	{ type = 0; }
+	Expr() = default;
 	explicit Expr(BroExprTag arg_tag);
 
 	virtual void ExprDescribe(ODesc* d) const = 0;
@@ -225,9 +225,9 @@ protected:
 	void RuntimeErrorWithCallStack(const std::string& msg) const;
 
 	BroExprTag tag;
-	BroType* type;
+	BroType* type = nullptr;
 
-	int paren;
+	bool paren;
 };
 
 class NameExpr : public Expr {
@@ -240,7 +240,7 @@ public:
 	Val* Eval(Frame* f) const override;
 	void Assign(Frame* f, Val* v) override;
 	Expr* MakeLvalue() override;
-	int IsPure() const override;
+	bool IsPure() const override;
 
 	TraversalCode Traverse(TraversalCallback* cb) const override;
 
@@ -276,7 +276,7 @@ public:
 	// vectors correctly as necessary.
 	Val* Eval(Frame* f) const override;
 
-	int IsPure() const override;
+	bool IsPure() const override;
 
 	TraversalCode Traverse(TraversalCallback* cb) const override;
 
@@ -297,7 +297,7 @@ public:
 	Expr* Op1() const	{ return op1; }
 	Expr* Op2() const	{ return op2; }
 
-	int IsPure() const override;
+	bool IsPure() const override;
 
 	// BinaryExpr::Eval correctly handles vector types.  Any child
 	// class that overrides Eval() should be modified to handle
@@ -366,7 +366,7 @@ public:
 
 	Val* Eval(Frame* f) const override;
 	Val* DoSingleEval(Frame* f, Val* v) const;
-	int IsPure() const override;
+	bool IsPure() const override;
 };
 
 class ComplementExpr : public UnaryExpr {
@@ -490,7 +490,7 @@ public:
 	const Expr* Op3() const	{ return op3; }
 
 	Val* Eval(Frame* f) const override;
-	int IsPure() const override;
+	bool IsPure() const override;
 
 	TraversalCode Traverse(TraversalCallback* cb) const override;
 
@@ -520,9 +520,9 @@ public:
 	Val* Eval(Frame* f) const override;
 	void EvalIntoAggregate(const BroType* t, Val* aggr, Frame* f) const override;
 	BroType* InitType() const override;
-	int IsRecordElement(TypeDecl* td) const override;
+	bool IsRecordElement(TypeDecl* td) const override;
 	Val* InitVal(const BroType* t, Val* aggr) const override;
-	int IsPure() const override;
+	bool IsPure() const override;
 
 protected:
 	bool TypeCheck(attr_list* attrs = 0);
@@ -542,8 +542,8 @@ class IndexExpr : public BinaryExpr {
 public:
 	IndexExpr(Expr* op1, ListExpr* op2, bool is_slice = false);
 
-	int CanAdd() const override;
-	int CanDel() const override;
+	bool CanAdd() const override;
+	bool CanDel() const override;
 
 	void Add(Frame* f) override;
 	void Delete(Frame* f) override;
@@ -575,7 +575,7 @@ public:
 	int Field() const	{ return field; }
 	const char* FieldName() const	{ return field_name; }
 
-	int CanDel() const override;
+	bool CanDel() const override;
 
 	void Assign(Frame* f, Val* v) override;
 	void Delete(Frame* f) override;
@@ -677,7 +677,7 @@ public:
 	const char* FieldName() const	{ return field_name.c_str(); }
 
 	void EvalIntoAggregate(const BroType* t, Val* aggr, Frame* f) const override;
-	int IsRecordElement(TypeDecl* td) const override;
+	bool IsRecordElement(TypeDecl* td) const override;
 
 protected:
 	void ExprDescribe(ODesc* d) const override;
@@ -758,7 +758,7 @@ public:
 	ScheduleExpr(Expr* when, EventExpr* event);
 	~ScheduleExpr() override;
 
-	int IsPure() const override;
+	bool IsPure() const override;
 
 	Val* Eval(Frame* f) const override;
 
@@ -791,7 +791,7 @@ public:
 	Expr* Func() const	{ return func; }
 	ListExpr* Args() const	{ return args; }
 
-	int IsPure() const override;
+	bool IsPure() const override;
 
 	Val* Eval(Frame* f) const override;
 
@@ -861,10 +861,10 @@ public:
 	expr_list& Exprs()		{ return exprs; }
 
 	// True if the entire list represents pure values.
-	int IsPure() const override;
+	bool IsPure() const override;
 
 	// True if the entire list represents constant values.
-	int AllConst() const;
+	bool AllConst() const;
 
 	Val* Eval(Frame* f) const override;
 
@@ -943,7 +943,7 @@ val_list* eval_list(Frame* f, const ListExpr* l);
 // Returns true if e1 is "greater" than e2 - here "greater" is just
 // a heuristic, used with commutative operators to put them into
 // a canonical form.
-extern int expr_greater(const Expr* e1, const Expr* e2);
+extern bool expr_greater(const Expr* e1, const Expr* e2);
 
 // True if the given Val* has a vector type
 inline bool is_vector(Expr* e)	{ return e->Type()->Tag() == TYPE_VECTOR; }
diff --git a/src/IP.cc b/src/IP.cc
index c63344c88c..56adbca6e7 100644
--- a/src/IP.cc
+++ b/src/IP.cc
@@ -766,7 +766,7 @@ IPv6_Hdr_Chain* IPv6_Hdr_Chain::Copy(const ip6_hdr* new_hdr) const
 		{
 		reporter->InternalWarning("empty IPv6 header chain");
 		delete rval;
-		return 0;
+		return nullptr;
 		}
 
 	const u_char* new_data = (const u_char*)new_hdr;
diff --git a/src/IP.h b/src/IP.h
index 9067e45c43..287bcf8fad 100644
--- a/src/IP.h
+++ b/src/IP.h
@@ -148,11 +148,7 @@ public:
 	/**
 	 * Initializes the header chain from an IPv6 header structure.
 	 */
-	IPv6_Hdr_Chain(const struct ip6_hdr* ip6, int len) :
-#ifdef ENABLE_MOBILE_IPV6
-		homeAddr(0),
-#endif
-		finalDst(0)
+	IPv6_Hdr_Chain(const struct ip6_hdr* ip6, int len)
 		{ Init(ip6, len, false); }
 
 	~IPv6_Hdr_Chain();
@@ -236,23 +232,13 @@ protected:
 	// point to a fragment
 	friend class FragReassembler;
 
-	IPv6_Hdr_Chain() :
-		length(0),
-#ifdef ENABLE_MOBILE_IPV6
-		homeAddr(0),
-#endif
-		finalDst(0)
-		{}
+	IPv6_Hdr_Chain() = default;
 
 	/**
 	 * Initializes the header chain from an IPv6 header structure, and replaces
 	 * the first next protocol pointer field that points to a fragment header.
 	 */
-	IPv6_Hdr_Chain(const struct ip6_hdr* ip6, uint16_t next, int len) :
-#ifdef ENABLE_MOBILE_IPV6
-		homeAddr(0),
-#endif
-		finalDst(0)
+	IPv6_Hdr_Chain(const struct ip6_hdr* ip6, uint16_t next, int len)
 		{ Init(ip6, len, true, next); }
 
 	/**
@@ -282,20 +268,20 @@ protected:
 	/**
 	 * The summation of all header lengths in the chain in bytes.
 	 */
-	uint16_t length;
+	uint16_t length = 0;
 
 #ifdef ENABLE_MOBILE_IPV6
 	/**
 	 * Home Address of the packet's source as defined by Mobile IPv6 (RFC 6275).
 	 */
-	IPAddr* homeAddr;
+	IPAddr* homeAddr = nullptr;
 #endif
 
 	/**
 	 * The final destination address in chain's first Routing header that has
 	 * non-zero segments left.
 	 */
-	IPAddr* finalDst;
+	IPAddr* finalDst = nullptr;
 };
 
 /**
@@ -311,7 +297,7 @@ public:
 	 * @param arg_del whether to take ownership of \a arg_ip4 pointer's memory.
 	 */
 	IP_Hdr(const struct ip* arg_ip4, bool arg_del)
-		: ip4(arg_ip4), ip6(0), del(arg_del), ip6_hdrs(0)
+		: ip4(arg_ip4), del(arg_del)
 		{
 		}
 
@@ -327,9 +313,9 @@ public:
 	 * @param c an already-constructed header chain to take ownership of.
 	 */
 	IP_Hdr(const struct ip6_hdr* arg_ip6, bool arg_del, int len,
-	       const IPv6_Hdr_Chain* c = 0)
-		: ip4(0), ip6(arg_ip6), del(arg_del),
-		  ip6_hdrs(c ? c : new IPv6_Hdr_Chain(ip6, len))
+	       const IPv6_Hdr_Chain* c = nullptr)
+		: ip6(arg_ip6), ip6_hdrs(c ? c : new IPv6_Hdr_Chain(ip6, len)),
+		  del(arg_del)
 		{
 		}
 
@@ -397,8 +383,8 @@ public:
 		{
 		if ( ip4 )
 			return ((const u_char*) ip4) + ip4->ip_hl * 4;
-		else
-			return ((const u_char*) ip6) + ip6_hdrs->TotalLength();
+
+		return ((const u_char*) ip6) + ip6_hdrs->TotalLength();
 		}
 
 #ifdef ENABLE_MOBILE_IPV6
@@ -409,9 +395,9 @@ public:
 	const ip6_mobility* MobilityHeader() const
 		{
 		if ( ip4 )
-			return 0;
+			return nullptr;
 		else if ( (*ip6_hdrs)[ip6_hdrs->Size()-1]->Type() != IPPROTO_MOBILITY )
-			return 0;
+			return nullptr;
 		else
 			return (const ip6_mobility*)(*ip6_hdrs)[ip6_hdrs->Size()-1]->Data();
 		}
@@ -425,15 +411,20 @@ public:
 		{
 		if ( ip4 )
 			return ntohs(ip4->ip_len) - ip4->ip_hl * 4;
-		else
-			return ntohs(ip6->ip6_plen) + 40 - ip6_hdrs->TotalLength();
+
+		return ntohs(ip6->ip6_plen) + 40 - ip6_hdrs->TotalLength();
 		}
 
 	/**
 	 * Returns the length of the IP packet (length of headers and payload).
 	 */
 	uint32_t TotalLen() const
-		{ return ip4 ? ntohs(ip4->ip_len) : ntohs(ip6->ip6_plen) + 40; }
+		{
+		if ( ip4 )
+			return ntohs(ip4->ip_len);
+
+		return ntohs(ip6->ip6_plen) + 40;
+		}
 
 	/**
 	 * Returns length of IP packet header (includes extension headers for IPv6).
@@ -543,8 +534,8 @@ public:
 	RecordVal* BuildPktHdrVal(RecordVal* pkt_hdr, int sindex) const;
 
 private:
-	const struct ip* ip4;
-	const struct ip6_hdr* ip6;
+	const struct ip* ip4 = nullptr;
+	const struct ip6_hdr* ip6 = nullptr;
+	const IPv6_Hdr_Chain* ip6_hdrs = nullptr;
 	bool del;
-	const IPv6_Hdr_Chain* ip6_hdrs;
 };
diff --git a/src/IPAddr.h b/src/IPAddr.h
index 04ecf5e33e..ba423a5026 100644
--- a/src/IPAddr.h
+++ b/src/IPAddr.h
@@ -136,7 +136,7 @@ public:
 	/**
 	 * Destructor.
 	 */
-	~IPAddr() { };
+	~IPAddr() = default;
 
 	/**
 	 * Returns the address' family.
@@ -145,8 +145,8 @@ public:
 		{
 		if ( memcmp(in6.s6_addr, v4_mapped_prefix, 12) == 0 )
 			return IPv4;
-		else
-			return IPv6;
+
+		return IPv6;
 		}
 
 	/**
@@ -161,8 +161,8 @@ public:
 		{
 		if ( GetFamily() == IPv4 )
 			return in6.s6_addr[12] == 224;
-		else
-			return in6.s6_addr[0] == 0xff;
+
+		return in6.s6_addr[0] == 0xff;
 		}
 
 	/**
@@ -173,8 +173,8 @@ public:
 		if ( GetFamily() == IPv4 )
 			return ((in6.s6_addr[12] == 0xff) && (in6.s6_addr[13] == 0xff)
 				&& (in6.s6_addr[14] == 0xff) && (in6.s6_addr[15] == 0xff));
-		else
-			return false;
+
+		return false;
 		}
 
 	/**
@@ -305,25 +305,25 @@ public:
 	 * will be returned in dotted representation, IPv6 addresses in
 	 * compressed hex.
 	 */
-	string AsString() const;
+	std::string AsString() const;
 
 	/**
 	 * Returns a string representation of the address suitable for inclusion
 	 * in an URI.  For IPv4 addresses, this is the same as AsString(), but
 	 * IPv6 addresses are encased in square brackets.
 	 */
-	string AsURIString() const
+	std::string AsURIString() const
 		{
 		if ( GetFamily() == IPv4 )
 			return AsString();
-		else
-			return string("[") + AsString() + "]";
+
+		return string("[") + AsString() + "]";
 		}
 
 	/**
 	 * Returns a host-order, plain hex string representation of the address.
 	 */
-	string AsHexString() const;
+	std::string AsHexString() const;
 
 	/**
 	 * Returns a string representation of the address. This returns the
@@ -335,7 +335,7 @@ public:
 	 * Returns a reverse pointer name associated with the IP address.
 	 * For example, 192.168.0.1's reverse pointer is 1.0.168.192.in-addr.arpa.
 	 */
-	string PtrName() const;
+	std::string PtrName() const;
 
 	/**
 	 * Comparison operator for IP address.
@@ -528,7 +528,7 @@ public:
 	/**
 	 * Constructs a prefix 0/0.
 	 */
-	IPPrefix() : length(0)	{}
+	IPPrefix() = default;
 
 	/**
 	 * Constructs a prefix instance from an IPv4 address and a prefix
@@ -575,7 +575,7 @@ public:
 	/**
 	 * Destructor.
 	 */
-	~IPPrefix() { }
+	~IPPrefix() = default;
 
 	/**
 	 * Returns the prefix in the form of an IP address. The address will
@@ -625,7 +625,7 @@ public:
 	 * will be returned in dotted representation, IPv6 addresses in
 	 * compressed hex.
 	 */
-	string AsString() const;
+	std::string AsString() const;
 
 	operator std::string() const	{ return AsString(); }
 
@@ -715,5 +715,5 @@ public:
 
 private:
 	IPAddr prefix;	// We store it as an address with the non-prefix bits masked out via Mask().
-	uint8_t length;	// The bit length of the prefix relative to full IPv6 addr.
+	uint8_t length = 0;	// The bit length of the prefix relative to full IPv6 addr.
 };
diff --git a/src/PriorityQueue.cc b/src/PriorityQueue.cc
index 26d763d79a..355b3b2a26 100644
--- a/src/PriorityQueue.cc
+++ b/src/PriorityQueue.cc
@@ -9,11 +9,9 @@
 #include "Reporter.h"
 #include "util.h"
 
-PriorityQueue::PriorityQueue(int initial_size)
+PriorityQueue::PriorityQueue(int initial_size) : max_heap_size(initial_size)
 	{
-	max_heap_size = initial_size;
 	heap = new PQ_Element*[max_heap_size];
-	peak_heap_size = heap_size = cumulative_num = 0;
 	}
 
 PriorityQueue::~PriorityQueue()
diff --git a/src/PriorityQueue.h b/src/PriorityQueue.h
index 665a83aa07..05de50ee69 100644
--- a/src/PriorityQueue.h
+++ b/src/PriorityQueue.h
@@ -9,8 +9,8 @@ class PriorityQueue;
 
 class PQ_Element {
 public:
-	explicit PQ_Element(double t)	{ time = t; offset = -1; }
-	virtual ~PQ_Element()	{ }
+	explicit PQ_Element(double t) : time(t) 	{}
+	virtual ~PQ_Element() = default;
 
 	double Time() const	{ return time; }
 
@@ -20,9 +20,9 @@ public:
 	void MinimizeTime()	{ time = -HUGE_VAL; }
 
 protected:
-	PQ_Element()		{ time = 0; offset = -1; }
-	double time;
-	int offset;
+	PQ_Element() = default;
+	double time = 0.0;
+	int offset = -1;
 };
 
 class PriorityQueue {
@@ -35,8 +35,8 @@ public:
 		{
 		if ( heap_size == 0 )
 			return 0;
-		else
-			return heap[0];
+
+		return heap[0];
 		}
 
 	// Removes (and returns) top of queue.  Returns nil if the queue
@@ -89,9 +89,9 @@ protected:
 		SetElement(bin2, t);
 		}
 
-	PQ_Element** heap;
-	int heap_size;
-	int peak_heap_size;
-	int max_heap_size;
-	uint64_t cumulative_num;
+	PQ_Element** heap = nullptr;
+	int heap_size = 0;
+	int peak_heap_size = 0;
+	int max_heap_size = 0;
+	uint64_t cumulative_num = 0;
 };
diff --git a/src/Type.h b/src/Type.h
index e2c674b438..538d2871f5 100644
--- a/src/Type.h
+++ b/src/Type.h
@@ -301,12 +301,12 @@ public:
 		return (TypeType*) this;
 		}
 
-	int IsSet() const
+	bool IsSet() const
 		{
 		return tag == TYPE_TABLE && (YieldType() == 0);
 		}
 
-	int IsTable() const
+	bool IsTable() const
 		{
 		return tag == TYPE_TABLE && (YieldType() != 0);
 		}