cmd/compile/internal/gc: fix initialization logic

Also add relevant test.

Fixes #13343.

Change-Id: Ib1e65af1d643d501de89adee3618eddbf6c69c9e
Reviewed-on: https://go-review.googlesource.com/18159
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/gc/sinit.go

@@ -124,10 +124,10 @@ func init1(n *Node, out **NodeList) {
 			}
 
 		case OAS2FUNC, OAS2MAPR, OAS2DOTTYPE, OAS2RECV:
-			if defn.Initorder != InitNotStarted {
+			if defn.Initorder == InitDone {
 				break
 			}
-			defn.Initorder = InitDone
+			defn.Initorder = InitPending
 			for l := defn.Rlist; l != nil; l = l.Next {
 				init1(l.N, out)
 			}
@@ -135,6 +135,7 @@ func init1(n *Node, out **NodeList) {
 				Dump("nonstatic", defn)
 			}
 			*out = list(*out, defn)
+			defn.Initorder = InitDone
 		}
 	}
 

test/fixedbugs/bug13343.go

@@ -0,0 +1,18 @@
+// errorcheck
+
+// Copyright 2015 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
+
+var (
+	a, b = f() // ERROR "initialization loop|depends upon itself"
+	c    = b
+)
+
+func f() (int, int) {
+	return c, c
+}
+
+func main() {}