Fix tst-cmp.c build with GCC mainline [committed]

Fix tst-cmp.c build with GCC mainline [committed]

[Joseph Myers]

Building the testsuite with GCC mainline fails with
-Wstringop-overflow= errors in string/tst-cmp.c.  These are for calls
to strncmp and strncasecmp with SIZE_MAX size argument.  The tests are
deliberately using this size that would be dubious in normal code, so
this patch disables the warning for the calls in question.

Tested with build-many-glibcs.py for aarch64-linux-gnu.  Committed.

2018-06-20  Joseph Myers  <joseph@codesourcery.com>

	* string/tst-cmp.c: Include <libc-diag.h>.
	(strncmp_max): Disable -Wstringop-overflow= around call to
	strncmp.
	(strncasecmp_max): Disable -Wstringop-overflow= around call to
	strncasecmp.

diff --git a/string/tst-cmp.c b/string/tst-cmp.c
index 1a7f1c8..3b9f7b2 100644
--- a/string/tst-cmp.c
+++ b/string/tst-cmp.c
@@ -26,6 +26,7 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
+#include <libc-diag.h>
 
 static int
 signum (int val)
@@ -98,13 +99,27 @@ strncasecmp_64 (const char *left, const char *right)
 static int
 strncmp_max (const char *left, const char *right)
 {
+  DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (7, 0)
+  /* GCC 9 warns about the size passed to strncmp being larger than
+     PTRDIFF_MAX; the use of SIZE_MAX is deliberate here.  */
+  DIAG_IGNORE_NEEDS_COMMENT (9, "-Wstringop-overflow=");
+#endif
   return strncmp (left, right, SIZE_MAX);
+  DIAG_POP_NEEDS_COMMENT;
 }
 
 static int
 strncasecmp_max (const char *left, const char *right)
 {
+  DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (7, 0)
+  /* GCC 9 warns about the size passed to strncasecmp being larger
+     than PTRDIFF_MAX; the use of SIZE_MAX is deliberate here.  */
+  DIAG_IGNORE_NEEDS_COMMENT (9, "-Wstringop-overflow=");
+#endif
   return strncasecmp (left, right, SIZE_MAX);
+  DIAG_POP_NEEDS_COMMENT;
 }
 
 int

-- 
Joseph S. Myers
joseph@codesourcery.com