[FFmpeg-cvslog] avutil/attributes: add av_warn_unused_result

[Ganesh Ajjanagadde]

ffmpeg | branch: master | Ganesh Ajjanagadde <gajjanagadde at gmail.com> | Mon Oct  5 01:45:12 2015 -0400| [1d4af04adf99301e21d7364d72f5570f5219083a] | committer: Michael Niedermayer

avutil/attributes: add av_warn_unused_result

GCC 3.4 introduced an attribute warn_unused_result to warn when a programmer
discards the return value. Applying this judiciously across the codebase can help
in fixing a lot of problems. At a high level, functions which return error codes
should always be checked. More concretely, consider the functions ff_add_format
and the like in avfilter/formats.h. A quick examination shows that a large portion
of libavfilter fails to handle the associated errors, usually AVERROR(ENOMEM).
The above example was where I observed the utility of this, but it should be
useful in many places across the code base.

Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=1d4af04adf99301e21d7364d72f5570f5219083a
---

 libavutil/attributes.h |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libavutil/attributes.h b/libavutil/attributes.h
index 50e8eb3..5c6b9de 100644
--- a/libavutil/attributes.h
+++ b/libavutil/attributes.h
@@ -52,6 +52,12 @@
 #endif
 #endif
 
+#if AV_GCC_VERSION_AT_LEAST(3,4)
+#    define av_warn_unused_result __attribute__((warn_unused_result))
+#else
+#    define av_warn_unused_result
+#endif
+
 #if AV_GCC_VERSION_AT_LEAST(3,1)
 #    define av_noinline __attribute__((noinline))
 #elif defined(_MSC_VER)