Fix assignments to event arguments becoming visible to subsequent

handlers.

It's well known that changes to mutable event arguments, like tables,
become visible to all places where those values are used, including
subsequent handlers of the same event. However, there's a related case
that's more suprising: simply assigning *a new value* to an event
argument passes through, too. This commit fixes that behaviour. (We
even had a btest with a baseline reflecting the problen).

src/Func.cc

@@ -383,11 +383,7 @@ Val* BroFunc::Call(val_list* args, Frame* parent) const
 			FType()->FlavorString().c_str(), d.Description());
 		}
 
-	loop_over_list(*args, i)
-		f->SetElement(i, (*args)[i]);
-
 	stmt_flow_type flow = FLOW_NEXT;
-
 	Val* result = 0;
 
 	for ( size_t i = 0; i < bodies.size(); ++i )
@@ -397,6 +393,19 @@ Val* BroFunc::Call(val_list* args, Frame* parent) const
 				bodies[i].stmts->GetLocationInfo());
 
 		Unref(result);
+
+		loop_over_list(*args, j)
+			{
+			Val* arg = (*args)[j];
+			if ( f->NthElement(j) != arg )
+				{
+				// Either not yet set, or somebody reassigned
+				// the frame slot.
+				Ref(arg);
+				f->SetElement(j, arg);
+				}
+			}
+
 		f->Reset(args->length());
 
 		try
@@ -434,6 +443,11 @@ Val* BroFunc::Call(val_list* args, Frame* parent) const
 			}
 		}
 
+	// We have an extra Ref for each argument (so that they don't get
+	// deleted between bodies), release that.
+	loop_over_list(*args, k)
+		Unref((*args)[k]);
+
 	if ( Flavor() == FUNC_FLAVOR_HOOK )
 		{
 		if ( ! result )

testing/btest/Baseline/core.event-arg-reuse/output

@@ -0,0 +1,2 @@
+f1, 2
+f2, 1

testing/btest/Baseline/signatures.load-sigs/output

@@ -1,3 +1,3 @@
 [orig_h=141.142.220.118, orig_p=35642/tcp, resp_h=208.80.152.2, resp_p=80/tcp]
 works
-GET /images/wikimedia-button.png HTTP/1.1\x0d\x0aHost: meta.wikimedia.org\x0d\x0aUser-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Geck...
+GET /images/wikimedia-button.png HTTP/1.1\x0d\x0aHost: meta.wikimedia.org\x0d\x0aUser-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110303 Ubuntu/10.04 (lucid) Firefox/3.6.15\x0d\x0aAccept: image/png,image/*;q=0.8,*/*;q=0.5\x0d\x0aAccept-Language: en-us,en;q=0.5\x0d\x0aAccept-Encoding: gzip,deflate\x0d\x0aAccept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\x0d\x0aKeep-Alive: 115\x0d\x0aConnection: keep-alive\x0d\x0aReferer: http://www.wikipedia.org/\x0d\x0aIf-Modified-Since: Fri, 05 Nov 2010 16:00:03 GMT\x0d\x0aIf-None-Match: "97a-494505e0c46c0"\x0d\x0aCache-Control: max-age=0\x0d\x0a\x0d\x0a

testing/btest/core/event-arg-reuse.bro

@@ -0,0 +1,20 @@
+# TEST-DOC: Check that assignment to event parameters isn't visible to other handlers.
+#
+# @TEST-EXEC: bro -b %INPUT >output
+# @TEST-EXEC: btest-diff output
+
+event f(a: int) &priority=5
+	{
+	a = 2;
+	print "f1", a;
+	}
+
+event f(a: int) &priority=-5
+	{
+	print "f2", a;
+	}
+
+event bro_init()
+	{
+	event f(1);
+	}