[PATCH] Fix warning from latest GCC in tst-printf.c

[Steve Ellcey <sellcey@caviumnetworks.com>]

GCC 7.0 (prerelease) adds a a new warning, -Wformat-length, if it
thinks an snprintf call may go beyond the end of the buffer length
being written to.  This warning is an approximation since GCC may not
know how many characters a '%d' format will expand to, but it makes a
worse case guess and warns if that would take the print beyond the
buffer length.

Here is a fix for one GLIBC test that fails to compile due to this
warning.  I think we want to ignore the warning in this case and not
increase the buffer size because I believe the test is intentionally
trying to go beyond the buffer limit.

The warnings are coming from the snprintf statements at line 225 and
228 of the original stdio-common/tst-printf.c and I could do a push and
pop of the warning down at those lines but I thought it made more sense
to put it up with the other DIAG_IGNORE.

OK to checkin?

Steve Ellcey
sellcey@caviumnetworks.com


2016-10-20  Steve Ellcey  <sellcey@caviumnetworks.com>

	* stdio-common/tst-printf.c: Ignore -Wformat-length warning.


diff --git a/stdio-common/tst-printf.c b/stdio-common/tst-printf.c
index 2896b18..1ae1eea 100644
--- a/stdio-common/tst-printf.c
+++ b/stdio-common/tst-printf.c
@@ -32,6 +32,9 @@
    The compiler warnings are not useful here.  */
 DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
 
+/* Compiler warnings about format lengths should also be ignored.  */
+DIAG_IGNORE_NEEDS_COMMENT (7.0, "-Wformat-length");
+
 static void rfg1 (void);
 static void rfg2 (void);
 static void rfg3 (void);