[backport from gcc-4.7/trunk <mikpe@it.uu.se>]

gcc/

2011-05-02  Simon Martin  <simartin@users.sourceforge.net>

	PR c/35445
	* c-decl.c (finish_decl): Only create a composite if the types are
	compatible.

gcc/testsuite/

2011-05-02  Simon Martin  <simartin@users.sourceforge.net>

	PR c/35445
	* gcc.dg/pr35445.c: New test.

--- gcc-4.6.0/gcc/c-decl.c.~1~	2011-03-20 02:55:25.000000000 +0100
+++ gcc-4.6.0/gcc/c-decl.c	2011-05-16 23:45:29.000000000 +0200
@@ -4246,7 +4246,7 @@ finish_decl (tree decl, location_t init_
 		b_ext = b_ext->shadowed;
 	      if (b_ext)
 		{
-		  if (b_ext->u.type)
+		  if (b_ext->u.type && comptypes (b_ext->u.type, type))
 		    b_ext->u.type = composite_type (b_ext->u.type, type);
 		  else
 		    b_ext->u.type = type;
--- gcc-4.6.0/gcc/testsuite/gcc.dg/pr35445.c.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.6.0/gcc/testsuite/gcc.dg/pr35445.c	2011-05-16 23:45:29.000000000 +0200
@@ -0,0 +1,6 @@
+/* PR c/35445 */
+/* { dg-do "compile" } */
+
+extern int i;
+extern int i; /* { dg-message "was here" } */
+int i[] = { 0 }; /* { dg-error "conflicting types" } */