[PATCH][C] Fix PR52549

[Richard Guenther]

This fixes PR52549 - we are running into an overzealous assert
that wants to make sure we don't have PLUS_EXPR on pointers.
But that code does not really check this and falls foul of
the conversion removal code right before it that transforms
(void *)(a + b) to a + b.

Fixed as follows.

Bootstrap and regtest pending on x86_64-unknown-linux-gnu.

Ok?

Thanks,
Richard.

2012-04-12  Richard Guenther  <rguent...@suse.de>

        PR c/52549
        * c-typeck.c (pointer_diff): Remove bogus assert.

        * gcc.dg/pr52549.c: New testcase.

Index: gcc/c-typeck.c
===================================================================
--- gcc/c-typeck.c      (revision 186373)
+++ gcc/c-typeck.c      (working copy)
@@ -3446,8 +3446,6 @@ pointer_diff (location_t loc, tree op0,
   else
     con1 = op1;
 
-  gcc_assert (TREE_CODE (con0) != PLUS_EXPR
-             && TREE_CODE (con1) != PLUS_EXPR);
   if (TREE_CODE (con0) == POINTER_PLUS_EXPR)
     {
       lit0 = TREE_OPERAND (con0, 1);
Index: gcc/testsuite/gcc.dg/pr52549.c
===================================================================
--- gcc/testsuite/gcc.dg/pr52549.c      (revision 0)
+++ gcc/testsuite/gcc.dg/pr52549.c      (revision 0)
@@ -0,0 +1,6 @@
+/* { dg-do compile } */
+
+_mark (long obj, int i, char *a)
+{
+  (char *)&(((long *)(obj)) [i]) - a;
+}