Hi All,
This patch fixes a minor issue that can occur when issuing array bounds
warnings. In GNU C mode we allow empty lists and their upper bound is
initialized to -1. This confuses the array bound analysis in VRP and
in some cases we end up issuing false positives. This patch fixes
the issue by bailing out when a zero-length array is encountered.
OK for trunk?
gcc/
2013-08-30 Meador Inge <mead...@codesourcery.com>
* tree-vrp.c (check_array_ref): Bail out no emtpy arrays.
gcc/testsuite/
2013-08-30 Meador Inge <mead...@codesourcery.com>
* gcc.dg/Warray-bounds-11.c: New testcase.
Index: gcc/testsuite/gcc.dg/Warray-bounds-11.c
===================================================================
--- gcc/testsuite/gcc.dg/Warray-bounds-11.c (revision 0)
+++ gcc/testsuite/gcc.dg/Warray-bounds-11.c (revision 0)
@@ -0,0 +1,12 @@
+/* { 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;
+}
Index: gcc/tree-vrp.c
===================================================================
--- gcc/tree-vrp.c (revision 202088)
+++ gcc/tree-vrp.c (working copy)
@@ -6137,9 +6137,10 @@ check_array_ref (location_t location, tr
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
