From 67484a90faa6afb2acea2f36ddb8a976bdfd6b65 Mon Sep 17 00:00:00 2001
From: Jon Siwek <jsiwek@corelight.com>
Date: Wed, 30 Jan 2019 11:20:09 -0600
Subject: [PATCH 1/2] GH-211: improve consistency of how scripting errors are
 handled

Scripting errors/mistakes now consistently generate a runtime error
which have the behavior of unwinding the call stack all the way out of
the current event handler.

Before, such errors were not treated consistently and either aborted
the process entirely or emitted a message while continuing to execute
subsequent statements without well-defined behavior (possibly causing
a cascade of errors).

The previous behavior also would only unwind out of the current
function (if within a function body), not out the current event
handler, which is especially problematic for functions that return
a value: the caller is essentially left a mess with no way to deal
with it.

This also changes the behavior of the startup/initialization process
to abort if there's errors during bro_init() rather than continue one
to the main run loop.  The `allow_init_errors` option may change this
new, default behavior.
---
 doc                                           |   2 +-
 scripts/base/init-bare.bro                    |   6 ++
 scripts/base/utils/site.bro                   |   4 +-
 src/Expr.cc                                   | 102 ++++++++++--------
 src/Expr.h                                    |   4 +
 src/Func.cc                                   |   6 +-
 src/Reporter.cc                               |   2 +-
 src/Trigger.cc                                |  39 +++++--
 src/Val.cc                                    |  15 ++-
 src/Var.cc                                    |   9 +-
 src/bro.bif                                   |   2 +-
 src/main.cc                                   |  20 +++-
 testing/btest/Baseline/bifs.all_set/out       |   2 +-
 testing/btest/Baseline/core.div-by-zero/out   |  10 +-
 .../Baseline/core.expr-exception/reporter.log |  18 ++--
 testing/btest/Baseline/core.init-error/out    |   5 +
 .../core.reporter-error-in-handler/output     |   4 +-
 .../core.reporter-runtime-error/output        |   4 +-
 .../bro.output                                |   8 +-
 .../Baseline/language.common-mistakes/1.out   |   4 +
 .../Baseline/language.common-mistakes/2.out   |   2 +
 .../Baseline/language.common-mistakes/3.out   |   2 +
 .../language.expire-expr-error/output         |   2 +-
 .../language.expire-func-undef/output         |  38 +++----
 .../language.index-assignment-invalid/out     |   2 +-
 .../btest/Baseline/language.invalid_index/out |   6 +-
 .../Baseline/language.record-bad-ctor/out     |   5 +-
 .../Baseline/language.table-type-checking/out |   2 +-
 .../language.type-cast-error-dynamic/output   |   6 +-
 .../Baseline/language.uninitialized-local/out |   3 +-
 .../language.uninitialized-local2/out         |   2 +-
 .../language.when-unitialized-rhs/out         |   4 +-
 .../Baseline/plugins.reporter-hook/output     |   4 +-
 .../plugins.reporter-hook/reporter.log        |   2 +-
 .../.stderr                                   |   2 +-
 testing/btest/bifs/all_set.bro                |   2 +-
 testing/btest/bifs/any_set.bro                |   2 +-
 testing/btest/bifs/split.bro                  |   1 -
 testing/btest/btest.cfg                       |   1 +
 testing/btest/core/init-error.bro             |  22 ++++
 .../btest/core/leaks/broker/remote_event.test |   2 +-
 .../btest/core/leaks/broker/remote_log.test   |   2 +-
 testing/btest/core/reporter-runtime-error.bro |   2 +-
 testing/btest/language/common-mistakes.bro    |  95 ++++++++++++++++
 .../language/index-assignment-invalid.bro     |   4 +-
 testing/btest/language/invalid_index.bro      |  21 ++--
 .../language/type-cast-error-dynamic.bro      |  13 ++-
 .../btest/language/uninitialized-local.bro    |   1 -
 testing/scripts/gen-broxygen-docs.sh          |   2 +-
 49 files changed, 374 insertions(+), 144 deletions(-)
 create mode 100644 testing/btest/Baseline/core.init-error/out
 create mode 100644 testing/btest/Baseline/language.common-mistakes/1.out
 create mode 100644 testing/btest/Baseline/language.common-mistakes/2.out
 create mode 100644 testing/btest/Baseline/language.common-mistakes/3.out
 create mode 100644 testing/btest/core/init-error.bro
 create mode 100644 testing/btest/language/common-mistakes.bro

diff --git a/doc b/doc
index 5acafa0d34..9823bc0bcd 160000
--- a/doc
+++ b/doc
@@ -1 +1 @@
-Subproject commit 5acafa0d340a6f4096dccbe69b8fb62d7c9ce87f
+Subproject commit 9823bc0bcdbd8fb148bfdd2295afcc97de313a92
diff --git a/scripts/base/init-bare.bro b/scripts/base/init-bare.bro
index 600a507d4f..e0e9ec2551 100644
--- a/scripts/base/init-bare.bro
+++ b/scripts/base/init-bare.bro
@@ -4959,3 +4959,9 @@ const bits_per_uid: count = 96 &redef;
 ## and set up the old comm. system.  Deprecation warnings are still emitted
 ## when setting this flag, but they will not result in a fatal error.
 const old_comm_usage_is_ok: bool = F &redef;
+
+## Whether errors, such as scripting mistakes, during initialization
+## (:bro:see:`bro_init`) are allowed or whether they will cause the
+## process to terminate before it enters the main, run-time loop.
+## The ZEEK_ALLOW_INIT_ERRORS environment variable also controls this option.
+const allow_init_errors: bool = F &redef;
diff --git a/scripts/base/utils/site.bro b/scripts/base/utils/site.bro
index 696f091410..aa40e1b92b 100644
--- a/scripts/base/utils/site.bro
+++ b/scripts/base/utils/site.bro
@@ -120,13 +120,11 @@ function find_all_emails(ip: addr): set[string]
 	for ( i in one_to_32 )
 		{
 		tmp_subnet = mask_addr(ip, one_to_32[i]);
-		for ( email in local_admins[tmp_subnet] )
-			{
+		if ( tmp_subnet in local_admins )
 			for ( email in local_admins[tmp_subnet] )
 				{
 				if ( email != "" )
 					add output_values[email];
-				}
 			}
 		}
 	return output_values;
diff --git a/src/Expr.cc b/src/Expr.cc
index ba3e8b1143..cb932ff7ee 100644
--- a/src/Expr.cc
+++ b/src/Expr.cc
@@ -181,6 +181,27 @@ void Expr::ExprError(const char msg[])
 	SetError();
 	}
 
+void Expr::RuntimeError(const std::string& msg) const
+	{
+	reporter->ExprRuntimeError(this, "%s", msg.data());
+	}
+
+void Expr::RuntimeErrorWithCallStack(const std::string& msg) const
+	{
+	auto rcs = render_call_stack();
+
+	if ( rcs.empty() )
+		reporter->ExprRuntimeError(this, "%s", msg.data());
+	else
+		{
+		ODesc d;
+		d.SetShort();
+		Describe(&d);
+		reporter->RuntimeError(GetLocationInfo(), "%s, expression: %s, call stack: %s",
+		                       msg.data(), d.Description(), rcs.data());
+		}
+	}
+
 bool Expr::Serialize(SerialInfo* info) const
 	{
 	return SerialObj::Serialize(info);
@@ -272,7 +293,7 @@ Val* NameExpr::Eval(Frame* f) const
 		return v->Ref();
 	else
 		{
-		Error("value used but not set");
+		RuntimeError("value used but not set");
 		return 0;
 		}
 	}
@@ -580,7 +601,7 @@ Val* BinaryExpr::Eval(Frame* f) const
 
 		if ( v_op1->Size() != v_op2->Size() )
 			{
-			Error("vector operands are of different sizes");
+			RuntimeError("vector operands are of different sizes");
 			return 0;
 			}
 
@@ -707,7 +728,7 @@ Val* BinaryExpr::Fold(Val* v1, Val* v2) const
 		d2 = v2->InternalDouble();
 		}
 	else
-		Internal("bad type in BinaryExpr::Fold");
+		RuntimeErrorWithCallStack("bad type in BinaryExpr::Fold");
 
 	switch ( tag ) {
 #define DO_INT_FOLD(op) \
@@ -716,13 +737,13 @@ Val* BinaryExpr::Fold(Val* v1, Val* v2) const
 	else if ( is_unsigned ) \
 		u3 = u1 op u2; \
 	else \
-		Internal("bad type in BinaryExpr::Fold");
+		RuntimeErrorWithCallStack("bad type in BinaryExpr::Fold");
 
 #define DO_UINT_FOLD(op) \
 	if ( is_unsigned ) \
 		u3 = u1 op u2; \
 	else \
-		Internal("bad type in BinaryExpr::Fold");
+		RuntimeErrorWithCallStack("bad type in BinaryExpr::Fold");
 
 #define DO_FOLD(op) \
 	if ( is_integral ) \
@@ -750,7 +771,7 @@ Val* BinaryExpr::Fold(Val* v1, Val* v2) const
 		if ( is_integral )
 			{
 			if ( i2 == 0 )
-				reporter->ExprRuntimeError(this, "division by zero");
+				RuntimeError("division by zero");
 
 			i3 = i1 / i2;
 			}
@@ -758,14 +779,14 @@ Val* BinaryExpr::Fold(Val* v1, Val* v2) const
 		else if ( is_unsigned )
 			{
 			if ( u2 == 0 )
-				reporter->ExprRuntimeError(this, "division by zero");
+				RuntimeError("division by zero");
 
 			u3 = u1 / u2;
 			}
 		else
 			{
 			if ( d2 == 0 )
-				reporter->ExprRuntimeError(this, "division by zero");
+				RuntimeError("division by zero");
 
 			d3 = d1 / d2;
 			}
@@ -778,7 +799,7 @@ Val* BinaryExpr::Fold(Val* v1, Val* v2) const
 		if ( is_integral )
 			{
 			if ( i2 == 0 )
-				reporter->ExprRuntimeError(this, "modulo by zero");
+				RuntimeError("modulo by zero");
 
 			i3 = i1 % i2;
 			}
@@ -786,13 +807,13 @@ Val* BinaryExpr::Fold(Val* v1, Val* v2) const
 		else if ( is_unsigned )
 			{
 			if ( u2 == 0 )
-				reporter->ExprRuntimeError(this, "modulo by zero");
+				RuntimeError("modulo by zero");
 
 			u3 = u1 % u2;
 			}
 
 		else
-			Internal("bad type in BinaryExpr::Fold");
+			RuntimeErrorWithCallStack("bad type in BinaryExpr::Fold");
 		}
 
 		break;
@@ -1122,7 +1143,7 @@ Val* IncrExpr::DoSingleEval(Frame* f, Val* v) const
 
 		if ( k < 0 &&
 		     v->Type()->InternalType() == TYPE_INTERNAL_UNSIGNED )
-			Error("count underflow");
+			RuntimeError("count underflow");
 		}
 
 	 BroType* ret_type = Type();
@@ -1522,7 +1543,7 @@ Val* AddToExpr::Eval(Frame* f) const
 		{
 		VectorVal* vv = v1->AsVectorVal();
 		if ( ! vv->Assign(vv->Size(), v2) )
-			reporter->Error("type-checking failed in vector append");
+			RuntimeError("type-checking failed in vector append");
 		return v1;
 		}
 
@@ -1959,7 +1980,7 @@ Val* BoolExpr::Eval(Frame* f) const
 
 	if ( vec_v1->Size() != vec_v2->Size() )
 		{
-		Error("vector operands have different sizes");
+		RuntimeError("vector operands have different sizes");
 		return 0;
 		}
 
@@ -2344,7 +2365,7 @@ Val* CondExpr::Eval(Frame* f) const
 
 	if ( cond->Size() != a->Size() || a->Size() != b->Size() )
 		{
-		Error("vectors in conditional expression have different sizes");
+		RuntimeError("vectors in conditional expression have different sizes");
 		return 0;
 		}
 
@@ -2669,7 +2690,7 @@ Val* AssignExpr::Eval(Frame* f) const
 	{
 	if ( is_init )
 		{
-		Error("illegal assignment in initialization");
+		RuntimeError("illegal assignment in initialization");
 		return 0;
 		}
 
@@ -2709,7 +2730,7 @@ void AssignExpr::EvalIntoAggregate(const BroType* t, Val* aggr, Frame* f) const
 		{
 		if ( t->Tag() != TYPE_RECORD )
 			{
-			Error("not a record initializer", t);
+			RuntimeError("not a record initializer");
 			return;
 			}
 
@@ -2718,7 +2739,7 @@ void AssignExpr::EvalIntoAggregate(const BroType* t, Val* aggr, Frame* f) const
 
 		if ( field < 0 )
 			{
-			Error("no such field");
+			RuntimeError("no such field");
 			return;
 			}
 
@@ -2732,7 +2753,7 @@ void AssignExpr::EvalIntoAggregate(const BroType* t, Val* aggr, Frame* f) const
 		}
 
 	if ( op1->Tag() != EXPR_LIST )
-		Error("bad table insertion");
+		RuntimeError("bad table insertion");
 
 	TableVal* tv = aggr->AsTableVal();
 
@@ -2742,7 +2763,7 @@ void AssignExpr::EvalIntoAggregate(const BroType* t, Val* aggr, Frame* f) const
 		return;
 
 	if ( ! tv->Assign(index, v) )
-		Error("type clash in table assignment");
+		RuntimeError("type clash in table assignment");
 
 	Unref(index);
 	}
@@ -3008,7 +3029,7 @@ Val* IndexExpr::Eval(Frame* f) const
 			{
 			if ( v_v1->Size() != v_v2->Size() )
 				{
-				Error("size mismatch, boolean index and vector");
+				RuntimeError("size mismatch, boolean index and vector");
 				Unref(v_result);
 				return 0;
 				}
@@ -3096,14 +3117,14 @@ Val* IndexExpr::Fold(Val* v1, Val* v2) const
 		}
 
 	default:
-		Error("type cannot be indexed");
+		RuntimeError("type cannot be indexed");
 		break;
 	}
 
 	if ( v )
 		return v->Ref();
 
-	Error("no such index");
+	RuntimeError("no such index");
 	return 0;
 	}
 
@@ -3136,12 +3157,12 @@ void IndexExpr::Assign(Frame* f, Val* v, Opcode op)
 				auto vt = v->Type();
 				auto vtt = vt->Tag();
 				std::string tn = vtt == TYPE_RECORD ? vt->GetName() : type_name(vtt);
-				Internal(fmt(
+				RuntimeErrorWithCallStack(fmt(
 				  "vector index assignment failed for invalid type '%s', value: %s",
 				  tn.data(), d.Description()));
 				}
 			else
-				Internal("assignment failed with null value");
+				RuntimeErrorWithCallStack("assignment failed with null value");
 			}
 		break;
 
@@ -3155,21 +3176,21 @@ void IndexExpr::Assign(Frame* f, Val* v, Opcode op)
 				auto vt = v->Type();
 				auto vtt = vt->Tag();
 				std::string tn = vtt == TYPE_RECORD ? vt->GetName() : type_name(vtt);
-				Internal(fmt(
+				RuntimeErrorWithCallStack(fmt(
 				  "table index assignment failed for invalid type '%s', value: %s",
 				  tn.data(), d.Description()));
 				}
 			else
-				Internal("assignment failed with null value");
+				RuntimeErrorWithCallStack("assignment failed with null value");
 			}
 		break;
 
 	case TYPE_STRING:
-		Internal("assignment via string index accessor not allowed");
+		RuntimeErrorWithCallStack("assignment via string index accessor not allowed");
 		break;
 
 	default:
-		Internal("bad index expression type in assignment");
+		RuntimeErrorWithCallStack("bad index expression type in assignment");
 		break;
 	}
 
@@ -3269,9 +3290,6 @@ void FieldExpr::Assign(Frame* f, Val* v, Opcode opcode)
 	if ( IsError() )
 		return;
 
-	if ( field < 0 )
-		ExprError("no such field in record");
-
 	Val* op_v = op->Eval(f);
 	if ( op_v )
 		{
@@ -3298,7 +3316,7 @@ Val* FieldExpr::Fold(Val* v) const
 		return def_attr->AttrExpr()->Eval(0);
 	else
 		{
-		reporter->ExprRuntimeError(this, "field value missing");
+		RuntimeError("field value missing");
 		assert(false);
 		return 0; // Will never get here, but compiler can't tell.
 		}
@@ -3483,7 +3501,7 @@ Val* RecordConstructorExpr::Fold(Val* v) const
 	RecordType* rt = type->AsRecordType();
 
 	if ( lv->Length() != rt->NumFields() )
-		Internal("inconsistency evaluating record constructor");
+		RuntimeErrorWithCallStack("inconsistency evaluating record constructor");
 
 	RecordVal* rv = new RecordVal(rt);
 
@@ -3838,7 +3856,7 @@ Val* VectorConstructorExpr::Eval(Frame* f) const
 		Val* v = e->Eval(f);
 		if ( ! vec->Assign(i, v) )
 			{
-			Error(fmt("type mismatch at index %d", i), e);
+			RuntimeError(fmt("type mismatch at index %d", i));
 			return 0;
 			}
 		}
@@ -3997,7 +4015,7 @@ Val* ArithCoerceExpr::FoldSingleVal(Val* v, InternalTypeTag t) const
 		return val_mgr->GetCount(v->CoerceToUnsigned());
 
 	default:
-		Internal("bad type in CoerceExpr::Fold");
+		RuntimeErrorWithCallStack("bad type in CoerceExpr::Fold");
 		return 0;
 	}
 	}
@@ -4305,7 +4323,7 @@ Val* TableCoerceExpr::Fold(Val* v) const
 	TableVal* tv = v->AsTableVal();
 
 	if ( tv->Size() > 0 )
-		Internal("coercion of non-empty table/set");
+		RuntimeErrorWithCallStack("coercion of non-empty table/set");
 
 	return new TableVal(Type()->AsTableType(), tv->Attrs());
 	}
@@ -4349,7 +4367,7 @@ Val* VectorCoerceExpr::Fold(Val* v) const
 	VectorVal* vv = v->AsVectorVal();
 
 	if ( vv->Size() > 0 )
-		Internal("coercion of non-empty vector");
+		RuntimeErrorWithCallStack("coercion of non-empty vector");
 
 	return new VectorVal(Type()->Ref()->AsVectorType());
 	}
@@ -4410,7 +4428,7 @@ Val* FlattenExpr::Fold(Val* v) const
 			l->Append(fa->AttrExpr()->Eval(0));
 
 		else
-			reporter->ExprRuntimeError(this, "missing field value");
+			RuntimeError("missing field value");
 		}
 
 	return l;
@@ -5070,7 +5088,7 @@ Val* ListExpr::Eval(Frame* f) const
 		Val* ev = exprs[i]->Eval(f);
 		if ( ! ev )
 			{
-			Error("uninitialized list value");
+			RuntimeError("uninitialized list value");
 			Unref(v);
 			return 0;
 			}
@@ -5367,7 +5385,7 @@ void ListExpr::Assign(Frame* f, Val* v, Opcode op)
 	ListVal* lv = v->AsListVal();
 
 	if ( exprs.length() != lv->Vals()->length() )
-		ExprError("mismatch in list lengths");
+		RuntimeError("mismatch in list lengths");
 
 	loop_over_list(exprs, i)
 		exprs[i]->Assign(f, (*lv->Vals())[i]->Ref(), op);
@@ -5542,7 +5560,7 @@ Val* CastExpr::Eval(Frame* f) const
 		d.Add(" (nil $data field)");
 
 	Unref(v);
-	reporter->ExprRuntimeError(this, "%s", d.Description());
+	RuntimeError(d.Description());
 	return 0;  // not reached.
 	}
 
diff --git a/src/Expr.h b/src/Expr.h
index d7dc01807e..820de2b876 100644
--- a/src/Expr.h
+++ b/src/Expr.h
@@ -210,6 +210,10 @@ protected:
 	// TYPE_ERROR.
 	void ExprError(const char msg[]);
 
+	void RuntimeError(const std::string& msg) const;
+
+	void RuntimeErrorWithCallStack(const std::string& msg) const;
+
 	DECLARE_ABSTRACT_SERIAL(Expr);
 
 	BroExprTag tag;
diff --git a/src/Func.cc b/src/Func.cc
index abc9331473..cbbbef6fa5 100644
--- a/src/Func.cc
+++ b/src/Func.cc
@@ -467,7 +467,11 @@ Val* BroFunc::Call(val_list* args, Frame* parent) const
 
 		catch ( InterpreterException& e )
 			{
-			// Already reported, but we continue exec'ing remaining bodies.
+			// Already reported, but now determine whether to unwind further.
+			if ( Flavor() == FUNC_FLAVOR_FUNCTION )
+				throw;
+
+			// Continue exec'ing remaining bodies of hooks/events.
 			continue;
 			}
 
diff --git a/src/Reporter.cc b/src/Reporter.cc
index a21d0a0538..ba1196de21 100644
--- a/src/Reporter.cc
+++ b/src/Reporter.cc
@@ -451,7 +451,7 @@ void Reporter::DoLog(const char* prefix, EventHandlerPtr event, FILE* out,
 	if ( postfix && *postfix )
 		// Note, if you change this fmt string, adjust the additional
 		// buffer size above.
-		safe_snprintf(buffer + strlen(buffer), size - strlen(buffer), " [%s]", postfix);
+		safe_snprintf(buffer + strlen(buffer), size - strlen(buffer), " (%s)", postfix);
 
 	bool raise_event = true;
 
diff --git a/src/Trigger.cc b/src/Trigger.cc
index 3867c607fd..213707b6b8 100644
--- a/src/Trigger.cc
+++ b/src/Trigger.cc
@@ -42,12 +42,20 @@ TraversalCode TriggerTraversalCallback::PreExpr(const Expr* expr)
 		{
 		const IndexExpr* e = static_cast<const IndexExpr*>(expr);
 		BroObj::SuppressErrors no_errors;
-		Val* v = e->Eval(trigger->frame);
-		if ( v )
+
+		try
 			{
-			trigger->Register(v);
-			Unref(v);
+			Val* v = e->Eval(trigger->frame);
+
+			if ( v )
+				{
+				trigger->Register(v);
+				Unref(v);
+				}
 			}
+		catch ( InterpreterException& )
+			{ /* Already reported */ }
+
 		break;
 		}
 
@@ -132,7 +140,17 @@ Trigger::Trigger(Expr* arg_cond, Stmt* arg_body, Stmt* arg_timeout_stmts,
 		arg_frame->SetDelayed();
 		}
 
-	Val* timeout_val = arg_timeout ? arg_timeout->Eval(arg_frame) : 0;
+	Val* timeout_val = nullptr;
+
+	if ( arg_timeout )
+		{
+		try
+			{
+			timeout_val = arg_timeout->Eval(arg_frame);
+			}
+		catch ( InterpreterException& )
+			{ /* Already reported */ }
+		}
 
 	if ( timeout_val )
 		{
@@ -202,7 +220,16 @@ bool Trigger::Eval()
 	// constants.
 	Frame* f = frame->Clone();
 	f->SetTrigger(this);
-	Val* v = cond->Eval(f);
+
+	Val* v = nullptr;
+
+	try
+		{
+		v = cond->Eval(f);
+		}
+	catch ( InterpreterException& )
+		{ /* Already reported */ }
+
 	f->ClearTrigger();
 
 	if ( f->HasDelayed() )
diff --git a/src/Val.cc b/src/Val.cc
index d57cffa45b..a96d2b098e 100644
--- a/src/Val.cc
+++ b/src/Val.cc
@@ -2391,9 +2391,18 @@ double TableVal::GetExpireTime()
 	if ( ! expire_time )
 		return -1;
 
-	Val* timeout = expire_time->Eval(0);
-	double interval = (timeout ? timeout->AsInterval() : -1);
-	Unref(timeout);
+	double interval;
+
+	try
+		{
+		Val* timeout = expire_time->Eval(0);
+		interval = (timeout ? timeout->AsInterval() : -1);
+		Unref(timeout);
+		}
+	catch ( InterpreterException& e )
+		{
+		interval = -1;
+		}
 
 	if ( interval >= 0 )
 		return interval;
diff --git a/src/Var.cc b/src/Var.cc
index d4659023a0..8534fdd910 100644
--- a/src/Var.cc
+++ b/src/Var.cc
@@ -13,7 +13,14 @@
 
 static Val* init_val(Expr* init, const BroType* t, Val* aggr)
 	{
-	return init->InitVal(t, aggr);
+	try
+		{
+		return init->InitVal(t, aggr);
+		}
+	catch ( InterpreterException& e )
+		{
+		return nullptr;
+		}
 	}
 
 static void make_var(ID* id, BroType* t, init_class c, Expr* init,
diff --git a/src/bro.bif b/src/bro.bif
index 13b2b9aa2e..9d6c34584f 100644
--- a/src/bro.bif
+++ b/src/bro.bif
@@ -1223,7 +1223,7 @@ function any_set%(v: any%) : bool
 ##
 ## v: The boolean vector instance.
 ##
-## Returns: True iff all elements in *v* are true.
+## Returns: True iff all elements in *v* are true or there are no elements.
 ##
 ## .. bro:see:: any_set
 ##
diff --git a/src/main.cc b/src/main.cc
index 6c714d806f..2fdcd2189e 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -1161,7 +1161,16 @@ int main(int argc, char** argv)
 		stmt_flow_type flow;
 		Frame f(current_scope()->Length(), 0, 0);
 		g_frame_stack.push_back(&f);
-		stmts->Exec(&f, flow);
+
+		try
+			{
+			stmts->Exec(&f, flow);
+			}
+		catch ( InterpreterException& )
+			{
+			reporter->FatalError("failed to execute script statements at top-level scope");
+			}
+
 		g_frame_stack.pop_back();
 		}
 
@@ -1185,6 +1194,15 @@ int main(int argc, char** argv)
 	// Drain the event queue here to support the protocols framework configuring DPM
 	mgr.Drain();
 
+	if ( reporter->Errors() > 0 )
+		{
+		auto allow_init_errors = global_scope()->Lookup("allow_init_errors");
+
+		if ( ! allow_init_errors->ID_Val()->AsBool() &&
+		     ! getenv("ZEEK_ALLOW_INIT_ERRORS") )
+			reporter->FatalError("errors occurred while initializing");
+		}
+
 	broker_mgr->BroInitDone();
 	analyzer_mgr->DumpDebug();
 
diff --git a/testing/btest/Baseline/bifs.all_set/out b/testing/btest/Baseline/bifs.all_set/out
index ed4964b655..f776b10b48 100644
--- a/testing/btest/Baseline/bifs.all_set/out
+++ b/testing/btest/Baseline/bifs.all_set/out
@@ -1,3 +1,3 @@
 F
-F
+T
 T
diff --git a/testing/btest/Baseline/core.div-by-zero/out b/testing/btest/Baseline/core.div-by-zero/out
index f5524b0cbf..dca1894e32 100644
--- a/testing/btest/Baseline/core.div-by-zero/out
+++ b/testing/btest/Baseline/core.div-by-zero/out
@@ -1,5 +1,5 @@
-expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.div-by-zero/div-by-zero.bro, line 6: division by zero [a / b]
-expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.div-by-zero/div-by-zero.bro, line 11: division by zero [a / b]
-expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.div-by-zero/div-by-zero.bro, line 16: division by zero [a / b]
-expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.div-by-zero/div-by-zero.bro, line 21: modulo by zero [a % b]
-expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.div-by-zero/div-by-zero.bro, line 26: modulo by zero [a % b]
+expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.div-by-zero/div-by-zero.bro, line 6: division by zero (a / b)
+expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.div-by-zero/div-by-zero.bro, line 11: division by zero (a / b)
+expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.div-by-zero/div-by-zero.bro, line 16: division by zero (a / b)
+expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.div-by-zero/div-by-zero.bro, line 21: modulo by zero (a % b)
+expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.div-by-zero/div-by-zero.bro, line 26: modulo by zero (a % b)
diff --git a/testing/btest/Baseline/core.expr-exception/reporter.log b/testing/btest/Baseline/core.expr-exception/reporter.log
index d6e07b42b3..f546142dca 100644
--- a/testing/btest/Baseline/core.expr-exception/reporter.log
+++ b/testing/btest/Baseline/core.expr-exception/reporter.log
@@ -6,13 +6,13 @@
 #open	2011-03-18-19-06-08
 #fields	ts	level	message	location
 #types	time	enum	string	string
-1300475168.783842	Reporter::ERROR	field value missing [c$ftp]	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
-1300475168.915940	Reporter::ERROR	field value missing [c$ftp]	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
-1300475168.916118	Reporter::ERROR	field value missing [c$ftp]	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
-1300475168.918295	Reporter::ERROR	field value missing [c$ftp]	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
-1300475168.952193	Reporter::ERROR	field value missing [c$ftp]	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
-1300475168.952228	Reporter::ERROR	field value missing [c$ftp]	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
-1300475168.954761	Reporter::ERROR	field value missing [c$ftp]	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
-1300475168.962628	Reporter::ERROR	field value missing [c$ftp]	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
-1300475169.780331	Reporter::ERROR	field value missing [c$ftp]	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
+1300475168.783842	Reporter::ERROR	field value missing (c$ftp)	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
+1300475168.915940	Reporter::ERROR	field value missing (c$ftp)	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
+1300475168.916118	Reporter::ERROR	field value missing (c$ftp)	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
+1300475168.918295	Reporter::ERROR	field value missing (c$ftp)	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
+1300475168.952193	Reporter::ERROR	field value missing (c$ftp)	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
+1300475168.952228	Reporter::ERROR	field value missing (c$ftp)	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
+1300475168.954761	Reporter::ERROR	field value missing (c$ftp)	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
+1300475168.962628	Reporter::ERROR	field value missing (c$ftp)	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
+1300475169.780331	Reporter::ERROR	field value missing (c$ftp)	/da/home/robin/bro/master/testing/btest/.tmp/core.expr-exception/expr-exception.bro, line 10
 #close	2011-03-18-19-06-13
diff --git a/testing/btest/Baseline/core.init-error/out b/testing/btest/Baseline/core.init-error/out
new file mode 100644
index 0000000000..9e11a25179
--- /dev/null
+++ b/testing/btest/Baseline/core.init-error/out
@@ -0,0 +1,5 @@
+expression error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/core.init-error/init-error.bro, line 16: no such index (v[10])
+fatal error: errors occurred while initializing
+1st event
+2nd event
+3rd event
diff --git a/testing/btest/Baseline/core.reporter-error-in-handler/output b/testing/btest/Baseline/core.reporter-error-in-handler/output
index 2f92afe6b0..ab5309b659 100644
--- a/testing/btest/Baseline/core.reporter-error-in-handler/output
+++ b/testing/btest/Baseline/core.reporter-error-in-handler/output
@@ -1,3 +1,3 @@
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.reporter-error-in-handler/reporter-error-in-handler.bro, line 28: no such index (a[1])
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.reporter-error-in-handler/reporter-error-in-handler.bro, line 22: no such index (a[2])
+expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.reporter-error-in-handler/reporter-error-in-handler.bro, line 28: no such index (a[1])
+expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.reporter-error-in-handler/reporter-error-in-handler.bro, line 22: no such index (a[2])
 1st error printed on script level
diff --git a/testing/btest/Baseline/core.reporter-runtime-error/output b/testing/btest/Baseline/core.reporter-runtime-error/output
index c2ace6ceb6..695e2e2f81 100644
--- a/testing/btest/Baseline/core.reporter-runtime-error/output
+++ b/testing/btest/Baseline/core.reporter-runtime-error/output
@@ -1,2 +1,2 @@
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.reporter-runtime-error/reporter-runtime-error.bro, line 12: no such index (a[1])
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/core.reporter-runtime-error/reporter-runtime-error.bro, line 9: no such index (a[2])
+expression error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/core.reporter-runtime-error/reporter-runtime-error.bro, line 12: no such index (a[1])
+fatal error: failed to execute script statements at top-level scope
diff --git a/testing/btest/Baseline/core.when-interpreter-exceptions/bro.output b/testing/btest/Baseline/core.when-interpreter-exceptions/bro.output
index 200e850a12..27a90d137c 100644
--- a/testing/btest/Baseline/core.when-interpreter-exceptions/bro.output
+++ b/testing/btest/Baseline/core.when-interpreter-exceptions/bro.output
@@ -1,7 +1,7 @@
-expression error in /Users/jon/Projects/bro/bro/testing/btest/.tmp/core.when-interpreter-exceptions/when-interpreter-exceptions.bro, line 47: field value missing [myrecord$notset]
-expression error in /Users/jon/Projects/bro/bro/testing/btest/.tmp/core.when-interpreter-exceptions/when-interpreter-exceptions.bro, line 91: field value missing [myrecord$notset]
-expression error in /Users/jon/Projects/bro/bro/testing/btest/.tmp/core.when-interpreter-exceptions/when-interpreter-exceptions.bro, line 72: field value missing [myrecord$notset]
-expression error in /Users/jon/Projects/bro/bro/testing/btest/.tmp/core.when-interpreter-exceptions/when-interpreter-exceptions.bro, line 103: field value missing [myrecord$notset]
+expression error in /Users/jon/Projects/bro/bro/testing/btest/.tmp/core.when-interpreter-exceptions/when-interpreter-exceptions.bro, line 47: field value missing (myrecord$notset)
+expression error in /Users/jon/Projects/bro/bro/testing/btest/.tmp/core.when-interpreter-exceptions/when-interpreter-exceptions.bro, line 91: field value missing (myrecord$notset)
+expression error in /Users/jon/Projects/bro/bro/testing/btest/.tmp/core.when-interpreter-exceptions/when-interpreter-exceptions.bro, line 72: field value missing (myrecord$notset)
+expression error in /Users/jon/Projects/bro/bro/testing/btest/.tmp/core.when-interpreter-exceptions/when-interpreter-exceptions.bro, line 103: field value missing (myrecord$notset)
 received termination signal
 [f(F)]
 f() done, no exception, T
diff --git a/testing/btest/Baseline/language.common-mistakes/1.out b/testing/btest/Baseline/language.common-mistakes/1.out
new file mode 100644
index 0000000000..8070f84644
--- /dev/null
+++ b/testing/btest/Baseline/language.common-mistakes/1.out
@@ -0,0 +1,4 @@
+expression error in ./1.bro, line 9: field value missing (mr$f)
+bar start
+foo start
+other bro_init
diff --git a/testing/btest/Baseline/language.common-mistakes/2.out b/testing/btest/Baseline/language.common-mistakes/2.out
new file mode 100644
index 0000000000..dd62af107c
--- /dev/null
+++ b/testing/btest/Baseline/language.common-mistakes/2.out
@@ -0,0 +1,2 @@
+expression error in ./2.bro, line 7: no such index (t[nope])
+in foo
diff --git a/testing/btest/Baseline/language.common-mistakes/3.out b/testing/btest/Baseline/language.common-mistakes/3.out
new file mode 100644
index 0000000000..d914d399a7
--- /dev/null
+++ b/testing/btest/Baseline/language.common-mistakes/3.out
@@ -0,0 +1,2 @@
+expression error in ./3.bro, line 5: type-checking failed in vector append (v += ok)
+in foo
diff --git a/testing/btest/Baseline/language.expire-expr-error/output b/testing/btest/Baseline/language.expire-expr-error/output
index cf43dd4c80..dfa0bf64c3 100644
--- a/testing/btest/Baseline/language.expire-expr-error/output
+++ b/testing/btest/Baseline/language.expire-expr-error/output
@@ -1,2 +1,2 @@
-error in /home/robin/bro/master/testing/btest/.tmp/language.expire-expr-error/expire-expr-error.bro, line 8: no such index (x[kaputt])
+expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-expr-error/expire-expr-error.bro, line 8: no such index (x[kaputt])
 received termination signal
diff --git a/testing/btest/Baseline/language.expire-func-undef/output b/testing/btest/Baseline/language.expire-func-undef/output
index 05b71a9908..cf869bbe6b 100644
--- a/testing/btest/Baseline/language.expire-func-undef/output
+++ b/testing/btest/Baseline/language.expire-func-undef/output
@@ -1,20 +1,20 @@
-1299470395.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299470405.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299473995.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299474005.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299477595.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299477605.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299481195.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299481205.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299484795.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299484805.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299488395.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299488405.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299491995.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299492005.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299495595.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299495605.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299499195.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299499205.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
-1299502795.000000 error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299470395.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299470405.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299473995.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299474005.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299477595.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299477605.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299481195.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299481205.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299484795.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299484805.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299488395.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299488405.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299491995.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299492005.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299495595.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299495605.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299499195.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299499205.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
+1299502795.000000 expression error in /home/robin/bro/master/testing/btest/.tmp/language.expire-func-undef/expire-func-undef.bro, line 12: value used but not set (segfault::scan_summary)
 orig: 10.0.0.2: peers: {\x0a\x0910.0.0.3\x0a}
diff --git a/testing/btest/Baseline/language.index-assignment-invalid/out b/testing/btest/Baseline/language.index-assignment-invalid/out
index 9b8b47be9d..3972a9f10e 100644
--- a/testing/btest/Baseline/language.index-assignment-invalid/out
+++ b/testing/btest/Baseline/language.index-assignment-invalid/out
@@ -1,4 +1,4 @@
-internal error in /home/jon/pro/zeek/zeek/scripts/base/utils/queue.bro, line 152: vector index assignment failed for invalid type 'myrec', value: [a=T, b=hi, c=<uninitialized>] (Queue::ret[Queue::j]), call stack: 
+runtime error in /home/jon/pro/zeek/zeek/scripts/base/utils/queue.bro, line 152: vector index assignment failed for invalid type 'myrec', value: [a=T, b=hi, c=<uninitialized>], expression: Queue::ret[Queue::j], call stack: 
  #0 Queue::get_vector([initialized=T, vals={[2] = test,[6] = jkl;,[4] = asdf,[1] = goodbye,[5] = 3,[0] = hello,[3] = [a=T, b=hi, c=<uninitialized>]}, settings=[max_len=<uninitialized>], top=7, bottom=0, size=0], [hello, goodbye, test]) at /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.index-assignment-invalid/index-assignment-invalid.bro:19 
  #1 bar(55) at /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.index-assignment-invalid/index-assignment-invalid.bro:27 
  #2 foo(hi, 13) at /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.index-assignment-invalid/index-assignment-invalid.bro:39 
diff --git a/testing/btest/Baseline/language.invalid_index/out b/testing/btest/Baseline/language.invalid_index/out
index 9110a8979d..4ba0373e91 100644
--- a/testing/btest/Baseline/language.invalid_index/out
+++ b/testing/btest/Baseline/language.invalid_index/out
@@ -1,7 +1,5 @@
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.invalid_index/invalid_index.bro, line 8: no such index (foo[1])
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.invalid_index/invalid_index.bro, line 9: no such index (foo[2])
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.invalid_index/invalid_index.bro, line 12: no such index (foo2[1])
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.invalid_index/invalid_index.bro, line 13: no such index (foo2[2])
+expression error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.invalid_index/invalid_index.bro, line 10: no such index (foo[1])
+expression error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.invalid_index/invalid_index.bro, line 16: no such index (foo2[1])
 foo[0], 42
 foo2[0], 13
 done
diff --git a/testing/btest/Baseline/language.record-bad-ctor/out b/testing/btest/Baseline/language.record-bad-ctor/out
index 97f853b5a8..d30d0ab9d3 100644
--- a/testing/btest/Baseline/language.record-bad-ctor/out
+++ b/testing/btest/Baseline/language.record-bad-ctor/out
@@ -1,3 +1,2 @@
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.record-bad-ctor/record-bad-ctor.bro, line 6: no type given (asdfasdf)
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.record-bad-ctor/record-bad-ctor.bro, line 7: uninitialized list value ($ports=asdfasdf)
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.record-bad-ctor/record-bad-ctor.bro, line 7: bad record initializer ((coerce [$ports=asdfasdf] to record { ports:error; }))
+error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.record-bad-ctor/record-bad-ctor.bro, line 6: no type given (asdfasdf)
+expression error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.record-bad-ctor/record-bad-ctor.bro, line 7: uninitialized list value ($ports=asdfasdf)
diff --git a/testing/btest/Baseline/language.table-type-checking/out b/testing/btest/Baseline/language.table-type-checking/out
index 00a4bb2491..488cb83ab2 100644
--- a/testing/btest/Baseline/language.table-type-checking/out
+++ b/testing/btest/Baseline/language.table-type-checking/out
@@ -4,7 +4,7 @@ error in port and /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.tab
 error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.table-type-checking/table-type-checking.bro, line 10: inconsistent types in table constructor (table(one = 1))
 error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.table-type-checking/table-type-checking.bro, line 17: type clash in assignment (gda = gda2)
 error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.table-type-checking/table-type-checking.bro, line 21 and /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.table-type-checking/table-type-checking.bro, line 4: index type doesn't match table (three and list of port)
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.table-type-checking/table-type-checking.bro, line 21: type clash in table assignment (three = 3)
+expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.table-type-checking/table-type-checking.bro, line 21: type clash in table assignment (three = 3)
 error in port and /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.table-type-checking/table-type-checking.bro, line 26: type clash (port and thousand)
 error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.table-type-checking/table-type-checking.bro, line 26: inconsistent types in table constructor (table(thousand = 1000))
 error in port and /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.table-type-checking/table-type-checking.bro, line 32: type clash (port and thousand-one)
diff --git a/testing/btest/Baseline/language.type-cast-error-dynamic/output b/testing/btest/Baseline/language.type-cast-error-dynamic/output
index 8ebf0cc90e..7c4ec0332f 100644
--- a/testing/btest/Baseline/language.type-cast-error-dynamic/output
+++ b/testing/btest/Baseline/language.type-cast-error-dynamic/output
@@ -1,4 +1,4 @@
-expression error in /Users/jon/projects/bro/bro/testing/btest/.tmp/language.type-cast-error-dynamic/type-cast-error-dynamic.bro, line 11: invalid cast of value with type 'count' to type 'string' [a as string]
-expression error in /Users/jon/projects/bro/bro/testing/btest/.tmp/language.type-cast-error-dynamic/type-cast-error-dynamic.bro, line 11: invalid cast of value with type 'record { a:addr; b:port; }' to type 'string' [a as string]
-expression error in /Users/jon/projects/bro/bro/testing/btest/.tmp/language.type-cast-error-dynamic/type-cast-error-dynamic.bro, line 11: invalid cast of value with type 'record { data:opaque of Broker::Data; }' to type 'string' (nil $data field) [a as string]
+expression error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.type-cast-error-dynamic/type-cast-error-dynamic.bro, line 11: invalid cast of value with type 'count' to type 'string' (a as string)
+expression error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.type-cast-error-dynamic/type-cast-error-dynamic.bro, line 11: invalid cast of value with type 'record { a:addr; b:port; }' to type 'string' (a as string)
+expression error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.type-cast-error-dynamic/type-cast-error-dynamic.bro, line 11: invalid cast of value with type 'record { data:opaque of Broker::Data; }' to type 'string' (nil $data field) (a as string)
 data is string, F
diff --git a/testing/btest/Baseline/language.uninitialized-local/out b/testing/btest/Baseline/language.uninitialized-local/out
index f803415fe6..24d45d3456 100644
--- a/testing/btest/Baseline/language.uninitialized-local/out
+++ b/testing/btest/Baseline/language.uninitialized-local/out
@@ -1,2 +1 @@
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.uninitialized-local/uninitialized-local.bro, line 16: value used but not set (my_string)
-Continuing
+expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.uninitialized-local/uninitialized-local.bro, line 16: value used but not set (my_string)
diff --git a/testing/btest/Baseline/language.uninitialized-local2/out b/testing/btest/Baseline/language.uninitialized-local2/out
index 75d09294e6..bba567878e 100644
--- a/testing/btest/Baseline/language.uninitialized-local2/out
+++ b/testing/btest/Baseline/language.uninitialized-local2/out
@@ -1,2 +1,2 @@
-error in /home/jon/projects/bro/bro/testing/btest/.tmp/language.uninitialized-local2/uninitialized-local2.bro, line 19: value used but not set (var_b)
+expression error in /home/jon/projects/bro/bro/testing/btest/.tmp/language.uninitialized-local2/uninitialized-local2.bro, line 19: value used but not set (var_b)
 var_a is, baz
diff --git a/testing/btest/Baseline/language.when-unitialized-rhs/out b/testing/btest/Baseline/language.when-unitialized-rhs/out
index 620b384da2..6698887be0 100644
--- a/testing/btest/Baseline/language.when-unitialized-rhs/out
+++ b/testing/btest/Baseline/language.when-unitialized-rhs/out
@@ -1,5 +1,5 @@
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.when-unitialized-rhs/when-unitialized-rhs.bro, line 9: value used but not set (crashMe)
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.when-unitialized-rhs/when-unitialized-rhs.bro, line 14: value used but not set (x)
+expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.when-unitialized-rhs/when-unitialized-rhs.bro, line 9: value used but not set (crashMe)
+expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/language.when-unitialized-rhs/when-unitialized-rhs.bro, line 14: value used but not set (x)
 1
 2
 3
diff --git a/testing/btest/Baseline/plugins.reporter-hook/output b/testing/btest/Baseline/plugins.reporter-hook/output
index e5ed573e67..8f706ec644 100644
--- a/testing/btest/Baseline/plugins.reporter-hook/output
+++ b/testing/btest/Baseline/plugins.reporter-hook/output
@@ -1,10 +1,10 @@
  | Hook  Some Info <...>/reporter-hook.bro, line 16
  | Hook error An Error <...>/reporter-hook.bro, line 18
  | Hook error An Error that does not show up in the log <...>/reporter-hook.bro, line 19
- | Hook expression error field value missing [b$a] <...>/reporter-hook.bro, line 23
+ | Hook expression error field value missing (b$a) <...>/reporter-hook.bro, line 23
  | Hook warning A warning <...>/reporter-hook.bro, line 17
 <...>/reporter-hook.bro, line 16: Some Info
 error in <...>/reporter-hook.bro, line 18: An Error
 error in <...>/reporter-hook.bro, line 19: An Error that does not show up in the log
-expression error in <...>/reporter-hook.bro, line 23: field value missing [b$a]
+expression error in <...>/reporter-hook.bro, line 23: field value missing (b$a)
 warning in <...>/reporter-hook.bro, line 17: A warning
diff --git a/testing/btest/Baseline/plugins.reporter-hook/reporter.log b/testing/btest/Baseline/plugins.reporter-hook/reporter.log
index ab70b0c17a..bce2fb909f 100644
--- a/testing/btest/Baseline/plugins.reporter-hook/reporter.log
+++ b/testing/btest/Baseline/plugins.reporter-hook/reporter.log
@@ -9,5 +9,5 @@
 0.000000	Reporter::INFO	Some Info	/Users/johanna/corelight/bro/testing/btest/.tmp/plugins.reporter-hook/reporter-hook.bro, line 16
 0.000000	Reporter::WARNING	A warning	/Users/johanna/corelight/bro/testing/btest/.tmp/plugins.reporter-hook/reporter-hook.bro, line 17
 0.000000	Reporter::ERROR	An Error	/Users/johanna/corelight/bro/testing/btest/.tmp/plugins.reporter-hook/reporter-hook.bro, line 18
-0.000000	Reporter::ERROR	field value missing [b$a]	/Users/johanna/corelight/bro/testing/btest/.tmp/plugins.reporter-hook/reporter-hook.bro, line 23
+0.000000	Reporter::ERROR	field value missing (b$a)	/Users/johanna/corelight/bro/testing/btest/.tmp/plugins.reporter-hook/reporter-hook.bro, line 23
 #close	2017-07-26-17-58-52
diff --git a/testing/btest/Baseline/scripts.base.frameworks.reporter.stderr/.stderr b/testing/btest/Baseline/scripts.base.frameworks.reporter.stderr/.stderr
index dc5065f5c8..ed161b2409 100644
--- a/testing/btest/Baseline/scripts.base.frameworks.reporter.stderr/.stderr
+++ b/testing/btest/Baseline/scripts.base.frameworks.reporter.stderr/.stderr
@@ -1 +1 @@
-error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/scripts.base.frameworks.reporter.stderr/stderr.bro, line 9: no such index (test[3])
+expression error in /Users/jsiwek/Projects/bro/bro/testing/btest/.tmp/scripts.base.frameworks.reporter.stderr/stderr.bro, line 9: no such index (test[3])
diff --git a/testing/btest/bifs/all_set.bro b/testing/btest/bifs/all_set.bro
index 67ae36622b..56f7b6e7f2 100644
--- a/testing/btest/bifs/all_set.bro
+++ b/testing/btest/bifs/all_set.bro
@@ -7,7 +7,7 @@ event bro_init()
 	local a = vector( T, F, T );
 	print all_set(a);
 
-	local b = vector();
+	local b: vector of bool = vector();
 	print all_set(b);
 
 	local c = vector( T );
diff --git a/testing/btest/bifs/any_set.bro b/testing/btest/bifs/any_set.bro
index 9f3f364556..b3e9e3c711 100644
--- a/testing/btest/bifs/any_set.bro
+++ b/testing/btest/bifs/any_set.bro
@@ -7,7 +7,7 @@ event bro_init()
 	local a = vector( F, T, F );
 	print any_set(a);
 
-	local b = vector();
+	local b: vector of bool = vector();
 	print any_set(b);
 
 	local c = vector( F );
diff --git a/testing/btest/bifs/split.bro b/testing/btest/bifs/split.bro
index 4fd994ce41..b117844645 100644
--- a/testing/btest/bifs/split.bro
+++ b/testing/btest/bifs/split.bro
@@ -17,7 +17,6 @@ event bro_init()
 	print b[1];
 	print b[2];
 	print b[3];
-	print b[4];
 	print "---------------------";
 	print c[1];
 	print c[2];
diff --git a/testing/btest/btest.cfg b/testing/btest/btest.cfg
index 6624d70431..5a570d9021 100644
--- a/testing/btest/btest.cfg
+++ b/testing/btest/btest.cfg
@@ -28,3 +28,4 @@ BRO_DEFAULT_LISTEN_ADDRESS=127.0.0.1
 BRO_DEFAULT_LISTEN_RETRY=1
 BRO_DEFAULT_CONNECT_RETRY=1
 BRO_DISABLE_BROXYGEN=1
+ZEEK_ALLOW_INIT_ERRORS=1
diff --git a/testing/btest/core/init-error.bro b/testing/btest/core/init-error.bro
new file mode 100644
index 0000000000..c8c1018324
--- /dev/null
+++ b/testing/btest/core/init-error.bro
@@ -0,0 +1,22 @@
+# The default is for an initialization error to be a hard failure.
+# Behavior may be changed via the `allow_init_errors` option.
+
+# @TEST-EXEC-FAIL: unset ZEEK_ALLOW_INIT_ERRORS && bro -b %INPUT >out 2>&1
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff out
+
+event bro_init() &priority=10
+	{
+	print "1st event";
+	}
+
+event bro_init() &priority=10
+	{
+	print "2nd event";
+	local v = vector(1, 2, 3);
+	print v[10];
+	}
+
+event bro_init() &priority=-10
+	{
+	print "3rd event";
+	}
diff --git a/testing/btest/core/leaks/broker/remote_event.test b/testing/btest/core/leaks/broker/remote_event.test
index e11d083db3..5000bd98d7 100644
--- a/testing/btest/core/leaks/broker/remote_event.test
+++ b/testing/btest/core/leaks/broker/remote_event.test
@@ -60,7 +60,7 @@ global event_count = 0;
 
 event Broker::peer_added(endpoint: Broker::EndpointInfo, msg: string)
 	{
-	print "Broker peer added", endpoint$network;
+	print "Broker peer added", endpoint$network$address;
 	Broker::publish("bro/event/hi", event_handler, "ping", event_count);
 	++event_count;
 	}
diff --git a/testing/btest/core/leaks/broker/remote_log.test b/testing/btest/core/leaks/broker/remote_log.test
index 4d55705e4a..12abc1a313 100644
--- a/testing/btest/core/leaks/broker/remote_log.test
+++ b/testing/btest/core/leaks/broker/remote_log.test
@@ -81,7 +81,7 @@ event do_write()
 
 event Broker::peer_added(endpoint: Broker::EndpointInfo, msg: string)
 	{
-	print "Broker peer added", endpoint$network;
+	print "Broker peer added", endpoint$network$address;
 	event do_write();
 	}
 
diff --git a/testing/btest/core/reporter-runtime-error.bro b/testing/btest/core/reporter-runtime-error.bro
index 330e2a7e5c..f8dd8c504c 100644
--- a/testing/btest/core/reporter-runtime-error.bro
+++ b/testing/btest/core/reporter-runtime-error.bro
@@ -1,5 +1,5 @@
 #
-# @TEST-EXEC: bro %INPUT >output 2>&1
+# @TEST-EXEC-FAIL: bro %INPUT >output 2>&1
 # @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff output
 
 global a: table[count] of count;
diff --git a/testing/btest/language/common-mistakes.bro b/testing/btest/language/common-mistakes.bro
new file mode 100644
index 0000000000..361aae0ff4
--- /dev/null
+++ b/testing/btest/language/common-mistakes.bro
@@ -0,0 +1,95 @@
+# These tests show off common scripting mistakes, which should be
+# handled internally by way of throwing an exception to unwind out
+# of the current event handler body.
+
+# @TEST-EXEC: bro -b 1.bro >1.out 2>&1
+# @TEST-EXEC: btest-diff 1.out
+
+# @TEST-EXEC: bro -b 2.bro >2.out 2>&1
+# @TEST-EXEC: btest-diff 2.out
+
+# @TEST-EXEC: bro -b 3.bro >3.out 2>&1
+# @TEST-EXEC: btest-diff 3.out
+
+@TEST-START-FILE 1.bro
+type myrec: record {
+	f: string &optional;
+};
+
+function foo(mr: myrec)
+	{
+	print "foo start";
+	# Unitialized field access: unwind out of current event handler body
+	print mr$f;
+	# Unreachable
+	print "foo done";
+	}
+
+function bar()
+	{
+	print "bar start";
+	foo(myrec());
+	# Unreachable
+	print "bar done";
+	}
+
+event bro_init()
+	{
+	bar();
+	# Unreachable
+	print "bro_init done";
+	}
+
+event bro_init() &priority=-10
+	{
+	# Reachable
+	print "other bro_init";
+	}
+@TEST-END-FILE
+
+@TEST-START-FILE 2.bro
+function foo()
+	{
+	print "in foo";
+	local t: table[string] of string = table();
+
+	# Non-existing index access: (sub)expressions should not be evaluated
+	if ( t["nope"] == "nope" )
+		# Unreachable
+		print "yes";
+	else
+		# Unreachable
+		print "no";
+
+	# Unreachable
+	print "foo done";
+	}
+
+event bro_init()
+	{
+	foo();
+	# Unreachable
+	print "bro_init done";
+	}
+
+@TEST-END-FILE
+
+@TEST-START-FILE 3.bro
+function foo(v: vector of any)
+	{
+	print "in foo";
+	# Vector append incompatible element type
+	v += "ok";
+	# Unreachable
+	print "foo done";
+	}
+
+event bro_init()
+	{
+	local v: vector of count;
+	v += 1;
+	foo(v);
+	# Unreachable
+	print "bro_init done", v;
+	}
+@TEST-END-FILE
diff --git a/testing/btest/language/index-assignment-invalid.bro b/testing/btest/language/index-assignment-invalid.bro
index 19bf54ea20..68458eb149 100644
--- a/testing/btest/language/index-assignment-invalid.bro
+++ b/testing/btest/language/index-assignment-invalid.bro
@@ -1,5 +1,5 @@
-# @TEST-EXEC-FAIL: bro -b %INPUT >output 2>&1
-# @TEST-EXEC: grep "internal error" output >output2
+# @TEST-EXEC: bro -b %INPUT >output 2>&1
+# @TEST-EXEC: grep "error" output >output2
 # @TEST-EXEC: for i in 1 2 3 4 5; do cat output2 | cut -d'|' -f$i >>out; done
 # @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff out
 
diff --git a/testing/btest/language/invalid_index.bro b/testing/btest/language/invalid_index.bro
index 96b7fa78c5..23fdb50d06 100644
--- a/testing/btest/language/invalid_index.bro
+++ b/testing/btest/language/invalid_index.bro
@@ -4,12 +4,19 @@
 global foo: vector of count = { 42 };
 global foo2: table[count] of count = { [0] = 13 };
 
-print "foo[0]", foo[0];
-print "foo[1]", foo[1];
-print "foo[2]", foo[2];
+event bro_init()
+	{
+	print "foo[0]", foo[0];
+	print "foo[1]", foo[1];
+	}
 
-print "foo2[0]", foo2[0];
-print "foo2[1]", foo2[1];
-print "foo2[2]", foo2[2];
+event bro_init()
+	{
+	print "foo2[0]", foo2[0];
+	print "foo2[1]", foo2[1];
+	}
 
-print "done";
+event bro_done()
+	{
+	print "done";
+	}
diff --git a/testing/btest/language/type-cast-error-dynamic.bro b/testing/btest/language/type-cast-error-dynamic.bro
index 91fa212ce4..c18548b0c4 100644
--- a/testing/btest/language/type-cast-error-dynamic.bro
+++ b/testing/btest/language/type-cast-error-dynamic.bro
@@ -11,15 +11,22 @@ function cast_to_string(a: any)
 	print a as string;
 	}
 
+event bro_init()
+	{
+	cast_to_string(42);
+	}
+
 event bro_init()
 	{
 	local x: X;
 	x = [$a = 1.2.3.4, $b=1947/tcp];
-
-	cast_to_string(42);
 	cast_to_string(x);
-	cast_to_string(Broker::Data());
+	}
+
+event bro_init()
+	{
 	print "data is string", Broker::Data() is string;
+	cast_to_string(Broker::Data());
 	}
 
 
diff --git a/testing/btest/language/uninitialized-local.bro b/testing/btest/language/uninitialized-local.bro
index e1cc178c0a..ae486ebf1f 100644
--- a/testing/btest/language/uninitialized-local.bro
+++ b/testing/btest/language/uninitialized-local.bro
@@ -14,7 +14,6 @@ event testit()
 	local my_string: string;
 	local my_vector: vector of string;
 	my_vector[0] = my_string;
-	print "Continuing";
 	}
 
 event bro_init()
diff --git a/testing/scripts/gen-broxygen-docs.sh b/testing/scripts/gen-broxygen-docs.sh
index 5ba33235fa..11f1cb066e 100755
--- a/testing/scripts/gen-broxygen-docs.sh
+++ b/testing/scripts/gen-broxygen-docs.sh
@@ -30,7 +30,7 @@ export BRO_SEED_FILE=$source_dir/testing/btest/random.seed
 
 function run_bro
     {
-    bro -X $conf_file broxygen >/dev/null 2>$bro_error_file
+    ZEEK_ALLOW_INIT_ERRORS=1 bro -X $conf_file broxygen >/dev/null 2>$bro_error_file
 
     if [ $? -ne 0 ]; then
         echo "Failed running bro with broxygen config file $conf_file"

From 01a8418d7918a6775361921b0cb317755868c354 Mon Sep 17 00:00:00 2001
From: Jon Siwek <jsiwek@corelight.com>
Date: Wed, 30 Jan 2019 12:01:46 -0600
Subject: [PATCH 2/2] GH-208: change invalid subnet expressions to a runtime
 error

Rather than abort.
---
 src/Expr.cc                                   | 15 +++++++++-
 src/IPAddr.cc                                 | 30 ++++++++++++-------
 .../btest/Baseline/language.subnet-errors/out |  5 ++++
 testing/btest/language/subnet-errors.bro      | 26 ++++++++++++++++
 4 files changed, 65 insertions(+), 11 deletions(-)
 create mode 100644 testing/btest/Baseline/language.subnet-errors/out
 create mode 100644 testing/btest/language/subnet-errors.bro

diff --git a/src/Expr.cc b/src/Expr.cc
index cb932ff7ee..be186524ad 100644
--- a/src/Expr.cc
+++ b/src/Expr.cc
@@ -1795,7 +1795,20 @@ Val* DivideExpr::AddrFold(Val* v1, Val* v2) const
 	else
 		mask = static_cast<uint32>(v2->InternalInt());
 
-	return new SubNetVal(v1->AsAddr(), mask);
+	auto& a = v1->AsAddr();
+
+	if ( a.GetFamily() == IPv4 )
+		{
+		if ( mask > 32 )
+			RuntimeError(fmt("bad IPv4 subnet prefix length: %" PRIu32, mask));
+		}
+	else
+		{
+		if ( mask > 128 )
+			RuntimeError(fmt("bad IPv6 subnet prefix length: %" PRIu32, mask));
+		}
+
+	return new SubNetVal(a, mask);
 	}
 
 IMPLEMENT_SERIAL(DivideExpr, SER_DIVIDE_EXPR);
diff --git a/src/IPAddr.cc b/src/IPAddr.cc
index 7ccc3dce07..7917e82c29 100644
--- a/src/IPAddr.cc
+++ b/src/IPAddr.cc
@@ -216,7 +216,10 @@ IPPrefix::IPPrefix(const in4_addr& in4, uint8_t length)
 	: prefix(in4), length(96 + length)
 	{
 	if ( length > 32 )
-		reporter->InternalError("Bad in4_addr IPPrefix length : %d", length);
+		{
+		reporter->Error("Bad in4_addr IPPrefix length : %d", length);
+		this->length = 0;
+		}
 
 	prefix.Mask(this->length);
 	}
@@ -225,7 +228,10 @@ IPPrefix::IPPrefix(const in6_addr& in6, uint8_t length)
 	: prefix(in6), length(length)
 	{
 	if ( length > 128 )
-		reporter->InternalError("Bad in6_addr IPPrefix length : %d", length);
+		{
+		reporter->Error("Bad in6_addr IPPrefix length : %d", length);
+		this->length = 0;
+		}
 
 	prefix.Mask(this->length);
 	}
@@ -236,19 +242,23 @@ IPPrefix::IPPrefix(const IPAddr& addr, uint8_t length, bool len_is_v6_relative)
 	if ( prefix.GetFamily() == IPv4 && ! len_is_v6_relative )
 		{
 		if ( length > 32 )
-			reporter->InternalError("Bad IPAddr(v4) IPPrefix length : %d",
-			                        length);
-
-		this->length = length + 96;
+			{
+			reporter->Error("Bad IPAddr(v4) IPPrefix length : %d", length);
+			this->length = 0;
+			}
+		else
+			this->length = length + 96;
 		}
 
 	else
 		{
 		if ( length > 128 )
-			reporter->InternalError("Bad IPAddr(v6) IPPrefix length : %d",
-			                        length);
-
-		this->length = length;
+			{
+			reporter->Error("Bad IPAddr(v6) IPPrefix length : %d", length);
+			this->length = 0;
+			}
+		else
+			this->length = length;
 		}
 
 	prefix.Mask(this->length);
diff --git a/testing/btest/Baseline/language.subnet-errors/out b/testing/btest/Baseline/language.subnet-errors/out
new file mode 100644
index 0000000000..5d8e3d76da
--- /dev/null
+++ b/testing/btest/Baseline/language.subnet-errors/out
@@ -0,0 +1,5 @@
+expression error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.subnet-errors/subnet-errors.bro, line 9: bad IPv4 subnet prefix length: 33 (1.2.3.4 / i)
+expression error in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.subnet-errors/subnet-errors.bro, line 18: bad IPv6 subnet prefix length: 129 (:: / i)
+1.2.3.4/32
+::/128
+init last
diff --git a/testing/btest/language/subnet-errors.bro b/testing/btest/language/subnet-errors.bro
new file mode 100644
index 0000000000..fa98dcec48
--- /dev/null
+++ b/testing/btest/language/subnet-errors.bro
@@ -0,0 +1,26 @@
+# @TEST-EXEC: bro -b %INPUT >out 2>&1
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff out
+
+event bro_init()
+	{
+	local i = 32;
+	print 1.2.3.4/i;
+	++i;
+	print 1.2.3.4/i;
+	print "init 1";
+	}
+
+event bro_init()
+	{
+	local i = 128;
+	print [::]/i;
+	++i;
+	print [::]/i;
+	print "init 1";
+	}
+
+event bro_init() &priority=-10
+	{
+	print "init last";
+	}
+