break and continue fixes

labeled break/continue was using
first loop with any label,
not first loop with the right label.

R=ken
OCL=32453
CL=32458

src/cmd/6g/gobj.c

@@ -97,6 +97,8 @@ zaddr(Biobuf *b, Addr *a, int s)
 	switch(a->type) {
 
 	case D_BRANCH:
+		if(a->branch == nil)
+			fatal("unpatched branch");
 		a->offset = a->branch->loc;
 
 	default:

src/cmd/8g/gobj.c

@@ -97,6 +97,8 @@ zaddr(Biobuf *b, Addr *a, int s)
 	switch(a->type) {
 
 	case D_BRANCH:
+		if(a->branch == nil)
+			fatal("unpatched branch");
 		a->offset = a->branch->loc;
 
 	default:

src/cmd/gc/gen.c

@@ -162,7 +162,14 @@ gen(Node *n)
 	case OFALL:
 	case OXCASE:
 	case OXFALL:
+		break;
+
 	case OEMPTY:
+		// insert no-op so that
+		//	L:; for { }
+		// does not treat L as a label for the loop.
+		if(labellist && labellist->label == p3)
+			gused(N);
 		break;
 
 	case OBLOCK:
@@ -181,9 +188,11 @@ gen(Node *n)
 	case OBREAK:
 		if(n->left != N) {
 			for(lab=labellist; lab!=L; lab=lab->link) {
-				if(lab->breakpc != P) {
+				if(lab->sym == n->left->sym) {
+					if(lab->breakpc == P)
+						yyerror("invalid break label %S", n->left->sym);
 					gjmp(lab->breakpc);
-					break;
+					goto donebreak;
 				}
 			}
 			if(lab == L)
@@ -195,26 +204,30 @@ gen(Node *n)
 			break;
 		}
 		gjmp(breakpc);
+	donebreak:
 		break;
 
 	case OCONTINUE:
 		if(n->left != N) {
 			for(lab=labellist; lab!=L; lab=lab->link) {
-				if(lab->continpc != P) {
+				if(lab->sym == n->left->sym) {
+					if(lab->continpc == P)
+						yyerror("invalid continue label %S", n->left->sym);
 					gjmp(lab->continpc);
-					break;
+					goto donecont;
 				}
 			}
 			if(lab == L)
-				yyerror("break label not defined: %S", n->left->sym);
+				yyerror("continue label not defined: %S", n->left->sym);
 			break;
 		}
 
 		if(continpc == P) {
-			yyerror("gen: continue is not in a loop");
+			yyerror("continue is not in a loop");
 			break;
 		}
 		gjmp(continpc);
+	donecont:
 		break;
 
 	case OFOR:
@@ -224,15 +237,11 @@ gen(Node *n)
 		scontin = continpc;
 		continpc = pc;
 
-		// define break and cotinue labels
-		for(lab=labellist; lab!=L; lab=lab->link) {
-			if(lab->label != p3)
-				break;
-			if(lab->op == OLABEL) {
+		// define break and continue labels
+		if((lab = labellist) != L && lab->label == p3 && lab->op == OLABEL) {
 			lab->breakpc = breakpc;
 			lab->continpc = continpc;
 		}
-		}
 
 		gen(n->nincr);				// contin:	incr
 		patch(p1, pc);				// test:
@@ -268,13 +277,8 @@ gen(Node *n)
 		breakpc = gjmp(P);		// break:	goto done
 
 		// define break label
-		for(lab=labellist; lab!=L; lab=lab->link) {
-			if(lab->label != p3)
-				break;
-			if(lab->op == OLABEL) {
+		if((lab = labellist) != L && lab->label == p3 && lab->op == OLABEL)
 			lab->breakpc = breakpc;
-			}
-		}
 
 		patch(p1, pc);				// test:
 		genlist(n->nbody);				//		switch(test) body
@@ -288,13 +292,8 @@ gen(Node *n)
 		breakpc = gjmp(P);		// break:	goto done
 
 		// define break label
-		for(lab=labellist; lab!=L; lab=lab->link) {
-			if(lab->label != p3)
-				break;
-			if(lab->op == OLABEL) {
+		if((lab = labellist) != L && lab->label == p3 && lab->op == OLABEL)
 			lab->breakpc = breakpc;
-			}
-		}
 
 		patch(p1, pc);				// test:
 		genlist(n->nbody);				//		select() body

test/fixedbugs/bug178.go

@@ -0,0 +1,27 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+L:
+	for i := 0; i < 1; i++ {
+L1:
+		for {
+			break L;
+		}
+		panic("BUG: not reached - break");
+	}
+
+L2:
+	for i := 0; i < 1; i++ {
+L3:
+		for {
+			continue L2;
+		}
+		panic("BUG: not reached - continue");
+	}
+}

test/fixedbugs/bug179.go

@@ -0,0 +1,24 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+func main() {
+L:
+	for {
+		for {
+			break L2;	// ERROR "L2"
+			continue L2;	// ERROR "L2"
+		}
+	}
+
+L1:
+	x := 1;
+	for {
+		break L1;	// ERROR "L1"
+		continue L1;	// ERROR "L1"
+	}
+}

test/golden.out

@@ -88,9 +88,6 @@ panic PC=xxx
 =========== bugs/bug132.go
 BUG: compilation succeeds incorrectly
 
-=========== bugs/bug136.go
-BUG: should not compile
-
 =========== bugs/bug159.go
 abc: expected 4 5 6 got 4 4 -4
 BUG: bug159
@@ -227,6 +224,9 @@ fixedbugs/bug133.dir/bug2.go:11: undefined: bug0.T field i
 fixedbugs/bug133.dir/bug2.go:11: illegal types for operand: RETURN
 	int
 
+=========== fixedbugs/bug136.go
+fixedbugs/bug136.go:9: invalid break label L
+
 =========== fixedbugs/bug148.go
 2 3
 interface is main.T, not main.T·bug148·1