tree-vrp.c (check_array_ref): Bail out on zero-length arrays.

gcc/

2013-08-30  Meador Inge  <meadori@codesourcery.com>

	* tree-vrp.c (check_array_ref): Bail out on zero-length arrays.

gcc/testsuite/

2013-08-30  Meador Inge  <meadori@codesourcery.com>

	* gcc.dg/Warray-bounds-11.c: New testcase.

From-SVN: r202115

gcc/ChangeLog

+2013-08-30  Meador Inge  <meadori@codesourcery.com>
+
+	* tree-vrp.c (check_array_ref): Bail out on zero-length arrays.
+
 2013-08-30  Marek Polacek  <polacek@redhat.com>
 
 	* Makefile.in (ubsan.o): Add.

gcc/testsuite/ChangeLog

+2013-08-30  Meador Inge  <meadori@codesourcery.com>
+
+	* gcc.dg/Warray-bounds-11.c: New testcase.
+
 2013-08-30  Marek Polacek  <polacek@redhat.com>
 
 	* g++.dg/ubsan/div-by-zero-1.C: New test.

gcc/testsuite/gcc.dg/Warray-bounds-11.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -Warray-bounds -std=gnu99" } */
+/* Test zero-length arrays for GNU C.  */
+
+unsigned int a[] = { };
+unsigned int size_a;
+
+int test(void)
+{
+  /* This should not warn.  */
+  return size_a ? a[0] : 0;
+}

gcc/tree-vrp.c

@@ -6137,9 +6137,10 @@ check_array_ref (location_t location, tree ref, bool ignore_off_by_one)
   low_sub = up_sub = TREE_OPERAND (ref, 1);
   up_bound = array_ref_up_bound (ref);
 
-  /* Can not check flexible arrays.  */
+  /* Can not check flexible arrays or zero-length arrays.  */
   if (!up_bound
-      || TREE_CODE (up_bound) != INTEGER_CST)
+      || TREE_CODE (up_bound) != INTEGER_CST
+      || tree_int_cst_equal (up_bound, integer_minus_one_node))
     return;
 
   /* Accesses to trailing arrays via pointers may access storage