gc: better diagnosis of initialization loops

Fixes bug 292.

R=ken2
https://golang.org/cl/164093

src/cmd/gc/closure.c

@@ -152,9 +152,10 @@ walkclosure(Node *func, NodeList **init)
 
 	// create the function
 	xfunc = nod(ODCLFUNC, N, N);
-	snprint(namebuf, sizeof namebuf, "_f%.3ld", ++closgen);
+	snprint(namebuf, sizeof namebuf, "_func_%.3ld", ++closgen);
 	xfunc->nname = newname(lookup(namebuf));
 	xfunc->nname->ntype = xtype;
+	xfunc->nname->defn = xfunc;
 	declare(xfunc->nname, PFUNC);
 	xfunc->nname->funcdepth = func->funcdepth;
 	xfunc->funcdepth = func->funcdepth;

src/cmd/gc/dcl.c

@@ -167,6 +167,7 @@ declare(Node *n, int ctxt)
 	if(isblank(n))
 		return;
 
+	n->lineno = parserline();
 	s = n->sym;
 	gen = 0;
 	if(ctxt == PEXTERN) {

src/cmd/gc/go.h

@@ -351,7 +351,6 @@ enum
 	ODOT, ODOTPTR, ODOTMETH, ODOTINTER, OXDOT,
 	ODOTTYPE,
 	OEQ, ONE, OLT, OLE, OGE, OGT,
-	OFUNC,
 	OIND,
 	OINDEX, OINDEXSTR, OINDEXMAP,
 	OKEY, OPARAM,

src/cmd/gc/sinit.c

@@ -8,6 +8,10 @@
 
 #include	"go.h"
 
+static NodeList *initlist;
+static void init2(Node*, NodeList**);
+static void init2list(NodeList*, NodeList**);
+
 static void
 init1(Node *n, NodeList **out)
 {
@@ -34,20 +38,45 @@ init1(Node *n, NodeList **out)
 
 	if(n->initorder == 1)
 		return;
-	if(n->initorder == 2)
-		fatal("init loop");
+	if(n->initorder == 2) {
+		if(n->class == PFUNC)
+			return;
+		
+		// if there have already been errors printed,
+		// those errors probably confused us and
+		// there might not be a loop.  let the user
+		// fix those first.
+		flusherrors();
+		if(nerrors > 0)
+			errorexit();
+
+		print("initialization loop:\n");
+		for(l=initlist;; l=l->next) {
+			if(l->next == nil)
+				break;
+			l->next->end = l;
+		}
+		for(; l; l=l->end)
+			print("\t%L %S refers to\n", l->n->lineno, l->n->sym);
+		print("\t%L %S\n", n->lineno, n->sym);
+		errorexit();
+	}
+	n->initorder = 2;
+	l = malloc(sizeof *l);
+	l->next = initlist;
+	l->n = n;
+	l->end = nil;
+	initlist = l;
 
 	// make sure that everything n depends on is initialized.
 	// n->defn is an assignment to n
-	n->initorder = 2;
 	if(n->defn != N) {
 		switch(n->defn->op) {
 		default:
 			goto bad;
 
 		case ODCLFUNC:
-			for(l=n->defn->nbody; l; l=l->next)
-				init1(l->n, out);
+			init2list(n->defn->nbody, out);
 			break;
 
 		case OAS:
@@ -67,6 +96,11 @@ init1(Node *n, NodeList **out)
 			break;
 		}
 	}
+	l = initlist;
+	initlist = l->next;
+	if(l->n != n)
+		fatal("bad initlist");
+	free(l);
 	n->initorder = 1;
 	return;
 
@@ -75,6 +109,31 @@ bad:
 	fatal("init1: bad defn");
 }
 
+// recurse over n, doing init1 everywhere.
+static void
+init2(Node *n, NodeList **out)
+{
+	if(n == N || n->initorder == 1)
+		return;
+	init1(n, out);
+	init2(n->left, out);
+	init2(n->right, out);
+	init2(n->ntest, out);
+	init2list(n->ninit, out);
+	init2list(n->list, out);
+	init2list(n->rlist, out);
+	init2list(n->nbody, out);
+	init2list(n->nelse, out);
+}
+
+static void
+init2list(NodeList *l, NodeList **out)
+{
+	for(; l; l=l->next)
+		init2(l->n, out);
+}
+
+
 static void
 initreorder(NodeList *l, NodeList **out)
 {

src/cmd/gc/subr.c

@@ -753,7 +753,6 @@ goopnames[] =
 	[OEQ]		= "==",
 	[OFALL]		= "fallthrough",
 	[OFOR]		= "for",
-	[OFUNC]		= "func",
 	[OGE]		= ">=",
 	[OGOTO]		= "goto",
 	[OGT]		= ">",

test/fixedbugs/bug223.go

@@ -0,0 +1,21 @@
+// (! $G $D/$F.go) | grep 'initialization loop' >/dev/null || echo BUG: bug223
+
+// 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.
+
+// check that initialization loop is diagnosed
+// and that closure cannot be used to hide it.
+// error message is not standard format, so no errchk above.
+
+package main
+
+type F func()
+
+func f() {
+	if true {
+		_ = func() { _ = m }
+	}
+}
+
+var m = map[string]F{"f": f}