[patch] Fix PR c++/27820

[Lee Millward]

Hi,

The C++ front-end currently ICE's on the following invalid code snippet:

void foo()
{
    L: L: ;
}

In the bugzilla PR Andrew Pinski suggested the first portion of the
patch to define_label return error_mark_node when an invalid label is
detected. Unfortunately this simply swaps the ICE listed in the PR for
an ICE in the gimplifier. This is because finish_label_stmt doesn't
check to make sure that the label being returned to it from
define_label is valid or not before calling add_stmt.

The proposed patch below incorporates Andrew Pinski's initial
suggestion with a further ammendment to finish_label_stmt to check for
invalid labels before calling add_stmt.

Bootstrapped and regression tested successfully on i686-pc-linux-gnu,
ok for mainline and for 4.1/4.0 assuming bootstrap/reg test succeeds
there?

Cheers,
Lee.

cp/

2006-06-30  Lee Millward  <lee.millward@gmail.com>
	    Andrew Pinski  <pinskia@gmail.com>

	PR c++/27820
	* decl.c (define_label): Return error_mark_node on error.
	* semantics.c (finish_label_stmt): Don't call add_stmt
        for invalid labels.

testsuite/

2006-06-30  Lee Millward  <lee.millward@gmail.com>

	PR c++/27820
	* g++.dg/other/label1.C: New test.
-------------- next part --------------
Index: gcc/testsuite/g++.dg/other/label1.C
===================================================================
--- gcc/testsuite/g++.dg/other/label1.C	(revision 0)
+++ gcc/testsuite/g++.dg/other/label1.C	(revision 0)
@@ -0,0 +1,7 @@
+//PR c++/27820
+
+void foo()
+{
+    L: L: ; // { dg-error "duplicate label" }
+}
+
Index: gcc/cp/decl.c
===================================================================
--- gcc/cp/decl.c	(revision 115074)
+++ gcc/cp/decl.c	(working copy)
@@ -2538,7 +2538,10 @@ define_label (location_t location, tree 
     pedwarn ("label named wchar_t");
 
   if (DECL_INITIAL (decl) != NULL_TREE)
-    error ("duplicate label %qD", decl);
+    {
+      error ("duplicate label %qD", decl);
+      POP_TIMEVAR_AND_RETURN (TV_NAME_LOOKUP, error_mark_node);
+    }
   else
     {
       struct named_label_use_entry *use;
Index: gcc/cp/semantics.c
===================================================================
--- gcc/cp/semantics.c	(revision 115074)
+++ gcc/cp/semantics.c	(working copy)
@@ -1293,6 +1293,10 @@ tree
 finish_label_stmt (tree name)
 {
   tree decl = define_label (input_location, name);
+
+  if (decl == error_mark_node)
+    return error_mark_node;
+
   return add_stmt (build_stmt (LABEL_EXPR, decl));
 }