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From:   Eric Biggers <ebiggers@kernel.org>
To:     linux-ext4@vger.kernel.org
Subject: [PATCH 10/38] lib/blkid: suppress -Wunused-result warning in blkid_flush_cache()
Date:   Sat, 21 Jan 2023 12:32:02 -0800
Message-Id: <20230121203230.27624-11-ebiggers@kernel.org>
In-Reply-To: <20230121203230.27624-1-ebiggers@kernel.org>
References: <20230121203230.27624-1-ebiggers@kernel.org>
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From: Eric Biggers <ebiggers@google.com>

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>
---
 lib/blkid/save.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lib/blkid/save.c b/lib/blkid/save.c
index 036f07a4a..6f4499cfd 100644
--- 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)
-- 
2.39.0