cmd/gc: initialize t->width in dgcsym() if required

Update #5291.

R=golang-dev, daniel.morsing, iant, r
CC=golang-dev
https://golang.org/cl/8663052

src/cmd/gc/reflect.c

@@ -1046,6 +1046,9 @@ dgcsym1(Sym *s, int ot, Type *t, vlong *off, int stack_size)
 
 	if(t->align > 0 && (*off % t->align) != 0)
 		fatal("dgcsym1: invalid initial alignment, %T", t);
+
+	if(t->width == BADWIDTH)
+		dowidth(t);
 	
 	switch(t->etype) {
 	case TINT8:
@@ -1141,6 +1144,8 @@ dgcsym1(Sym *s, int ot, Type *t, vlong *off, int stack_size)
 	case TARRAY:
 		if(t->bound < -1)
 			fatal("dgcsym1: invalid bound, %T", t);
+		if(t->type->width == BADWIDTH)
+			dowidth(t->type);
 		if(isslice(t)) {
 			// NOTE: Any changes here need to be made to reflect.SliceOf as well.
 			// struct { byte* array; uint32 len; uint32 cap; }
@@ -1214,6 +1219,9 @@ dgcsym(Type *t)
 		return s;
 	s->flags |= SymGcgen;
 
+	if(t->width == BADWIDTH)
+		dowidth(t);
+
 	ot = 0;
 	off = 0;
 	ot = duintptr(s, ot, t->width);

test/fixedbugs/issue5291.dir/pkg1.go

@@ -0,0 +1,34 @@
+// Copyright 2013 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 pkg1
+
+import (
+	"runtime"
+)
+
+type T2 *[]string
+
+type Data struct {
+	T1 *[]T2
+}
+
+func CrashCall() (err error) {
+	var d Data
+
+	for count := 0; count < 10; count++ {
+		runtime.GC()
+
+		len := 2 // crash when >=2
+		x := make([]T2, len)
+
+		d = Data{T1: &x}
+
+		for j := 0; j < len; j++ {
+			y := make([]string, 1)
+			(*d.T1)[j] = &y
+		}
+	}
+	return nil
+}

test/fixedbugs/issue5291.dir/prog.go

@@ -0,0 +1,17 @@
+// Copyright 2013 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
+
+import (
+	"./pkg1"
+)
+
+type message struct { // Presence of this creates a crash
+	data pkg1.Data
+}
+
+func main() {
+	pkg1.CrashCall()
+}

test/fixedbugs/issue5291.go

@@ -0,0 +1,9 @@
+// rundir
+
+// Copyright 2013 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.
+
+// Issue 5291: GC crash
+
+package ignored