The following fixes spurious uninit warnings for zero-sized arrays.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
Richard.
2017-12-08 Richard Biener <rguent...@suse.de>
PR middle-end/81782
* tree-ssa-uninit.c (warn_uninitialized_vars): Properly
handle accesses outside of zero-sized vars.
* gcc.dg/uninit-pr81782.c: New testcase.
Index: gcc/tree-ssa-uninit.c
===================================================================
--- gcc/tree-ssa-uninit.c (revision 255499)
+++ gcc/tree-ssa-uninit.c (working copy)
@@ -296,8 +296,8 @@ warn_uninitialized_vars (bool warn_possi
variable. */
if (DECL_P (base)
&& ref.size != -1
- && ref.max_size == ref.size
- && (ref.offset + ref.size <= 0
+ && ((ref.max_size == ref.size
+ && ref.offset + ref.size <= 0)
|| (ref.offset >= 0
&& DECL_SIZE (base)
&& TREE_CODE (DECL_SIZE (base)) == INTEGER_CST
Index: gcc/testsuite/gcc.dg/uninit-pr81782.c
===================================================================
--- gcc/testsuite/gcc.dg/uninit-pr81782.c (nonexistent)
+++ gcc/testsuite/gcc.dg/uninit-pr81782.c (working copy)
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-Wmaybe-uninitialized" } */
+
+int
+foo (void)
+{
+ char empty_array[] = { };
+ int i, ret = 0;
+
+ for (i = 0; i < (int) (sizeof (empty_array) / sizeof (empty_array[0])); i++)
+ ret = empty_array[i]; /* { dg-bogus "uninitialized" } */
+
+ return ret;
+}
