[PATCH] Fix PR67271

[Richard Biener <rguenther@suse.de>]

Bootstrapped / tested on x86_64-unknown-linux-gnu, applied.

Richard.

2015-09-16  Richard Biener  <rguenther@suse.de>

	PR middle-end/67271
	* fold-const.c (native_encode_expr): Bail out on bogus offsets.

	* gcc.dg/pr67271.c: New testcase.

Index: gcc/fold-const.c
===================================================================
--- gcc/fold-const.c	(revision 227779)
+++ gcc/fold-const.c	(working copy)
@@ -7106,6 +7127,10 @@ native_encode_string (const_tree expr, u
 int
 native_encode_expr (const_tree expr, unsigned char *ptr, int len, int off)
 {
+  /* We don't support starting at negative offset and -1 is special.  */
+  if (off < -1)
+    return 0;
+
   switch (TREE_CODE (expr))
     {
     case INTEGER_CST:
Index: gcc/testsuite/gcc.dg/pr67271.c
===================================================================
--- gcc/testsuite/gcc.dg/pr67271.c	(revision 0)
+++ gcc/testsuite/gcc.dg/pr67271.c	(working copy)
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+extern long int labs (long int j);
+int
+main ()
+{
+  long *a = (long *)"empty";
+  int i = 1441516387;
+  a[i] = labs (a[i]);
+  return 0;
+}