Disable -Wformat-overflow= warnings for some printf tests.

Recent GCC -Wformat-overflow= changes result in some printf tests
failing to build, because those tests are deliberately testing the
handling of formats writing more than INT_MAX characters and the
handling of NULL arguments to the %s format, which GCC now warns
about.  This patch duly disables -Wformat-overflow= for the relevant
calls to printf functions.

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

	* stdio-common/bug22.c: Include <libc-diag.h>.
	(do_test): Disable -Wformat-overflow= warnings around fprintf
	calls outputting more than INT_MAX characters.
	* stdio-common/tst-printf.c: Disable -Wformat-overflow= warnings
	around printf call with NULL %s argument.

1 files changed, 7 insertions, 0 deletions

diff --git a/stdio-common/tst-printf.c b/stdio-common/tst-printf.c
index 70d9e58..e4f4f16 100644
--- a/stdio-common/tst-printf.c
+++ b/stdio-common/tst-printf.c
@@ -110,7 +110,14 @@ I am ready for my first lesson today.";
   printf("left-adjusted Z string:\t\"%-010s\"\n", shortstr);
   printf("space-padded string:\t\"%10s\"\n", shortstr);
   printf("left-adjusted S string:\t\"%-10s\"\n", shortstr);
+  /* GCC 9 warns about the NULL format argument; this is deliberately
+     tested here.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (7, 0)
+  DIAG_IGNORE_NEEDS_COMMENT (9, "-Wformat-overflow=");
+#endif
   printf("null string:\t\"%s\"\n", (char *)NULL);
+  DIAG_POP_NEEDS_COMMENT;
   printf("limited string:\t\"%.22s\"\n", longstr);
 
   printf("a-style max:\t\"%a\"\n", DBL_MAX);