lib/blkid: suppress -Wunused-result warning in blkid_flush_cache()

When _FORTIFY_SOURCE is defined, glibc annotates link() with the
warn_unused_result function attribute.  With gcc, that makes
'(void) link()' cause a -Wunused-result warning, despite the explicit
cast to void.  That's annoying, since the use case in lib/blkid/save.c
is legitimate (opportunistic backup).  So let's suppress this warning.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/lib/blkid/save.c b/lib/blkid/save.c
index 036f07a..6f4499c 100644 (file)
--- a/lib/blkid/save.c
+++ b/lib/blkid/save.c
@@ -154,7 +154,15 @@ int blkid_flush_cache(blkid_cache cache)
                        if (backup) {
                                sprintf(backup, "%s.old", filename);
                                unlink(backup);
+#if defined(__GNUC__) && __GNUC__ >= 5
+/* explicit (void) cast is not enough with glibc and _FORTIFY_SOURCE */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-result"
+#endif
                                (void) link(filename, backup);
+#if defined(__GNUC__) && __GNUC__ >= 5
+#pragma GCC diagnostic pop
+#endif
                                free(backup);
                        }
                        if (rename(opened, filename) < 0)