[FFmpeg-devel] [PATCH] avcodec: use HAVE_THREADS header guards to silence -Wunused-function

[Ganesh Ajjanagadde]

On Sat, Oct 3, 2015 at 2:25 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Sat, Oct 03, 2015 at 11:13:35AM -0400, Ronald S. Bultje wrote:
>> Hi,
>>
>> On Thu, Sep 17, 2015 at 7:51 AM, Michael Niedermayer <michaelni at gmx.at>
>> wrote:
>>
>> > On Thu, Sep 17, 2015 at 06:54:37AM -0400, Ganesh Ajjanagadde wrote:
>> > > On Thu, Sep 17, 2015 at 6:17 AM, Michael Niedermayer <michaelni at gmx.at>
>> > wrote:
>> > > > On Wed, Sep 16, 2015 at 10:22:27PM -0400, Ganesh Ajjanagadde wrote:
>> > > >> When compiled with --disable-pthreads, e.g
>> > > >>
>> > http://fate.ffmpeg.org/report.cgi?time=20150917015044&slot=alpha-debian-qemu-gcc-4.7
>> > ,
>> > > >> a bunch of -Wunused-functions are reported due to missing header
>> > guards
>> > > >> around threading related functions.
>> > > >> This patch should silence such warnings.
>> > > >>
>> > > >> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
>> > > >> ---
>> > > >>  libavcodec/alac.c          | 2 ++
>> > > >>  libavcodec/exr.c           | 2 ++
>> > > >>  libavcodec/ffv1dec.c       | 4 ++++
>> > > >>  libavcodec/flacdec.c       | 2 ++
>> > > >>  libavcodec/h264.c          | 2 ++
>> > > >>  libavcodec/huffyuvdec.c    | 2 ++
>> > > >>  libavcodec/mdec.c          | 2 ++
>> > > >>  libavcodec/mimic.c         | 4 ++++
>> > > >>  libavcodec/mpeg12dec.c     | 2 ++
>> > > >>  libavcodec/mpeg4videodec.c | 2 ++
>> > > >>  libavcodec/pngdec.c        | 2 ++
>> > > >>  libavcodec/takdec.c        | 2 ++
>> > > >>  libavcodec/tta.c           | 2 ++
>> > > >>  libavcodec/vp3.c           | 4 ++++
>> > > >>  libavcodec/vp8.c           | 2 ++
>> > > >>  libavcodec/vp9.c           | 2 ++
>> > > >>  libavcodec/wavpack.c       | 2 ++
>> > > >>  17 files changed, 40 insertions(+)
>> > > >
>> > > > av_unused might be simpler to silence these warnings than #if
>> > >
>> > > I do not think this is consistent at the moment across the codebase;
>> > > sometimes we use header guards and sometimes we use av_unused. Please
>> > > tell me if what the rationale is for either of them; I am fine either
>> > > way. Any half decent compiler should anyway remove unused functions
>> > > when compiled with optimizations.
>> >
>> > #ifs will be more work to maintain as they can break build if a new
>> > function call or function is added. av_unused cannot break build
>> > #ifs also make the code harder to read, especially if there are
>> > already some #ifs there before
>> >
>> > #ifs make sense for non static symbols as they cannot be removed by
>> > the compiler or linker generally
>> >
>> > #ifs could also be used to structure code in a file if for some
>> > reason its unwanted to split it in several files
>> > #ifs also gurantee that code is removed and this makes sense in
>> > performance critical code
>> > #ifs can be used for any group of lines not just functions/variables
>> > as for av_unused
>>
>>
>> Michael, how strong is your objection here? Me and wm4 seem to have a
>> slight preference for #if over av_unused, since av_unused runs the risk of
>> rotting with code over time.
>
> iam almost neutral to the #if vs ununsed vs nothing question.
> i just felt that av_unused would be less work to maintain than #if,
> iam fine with any of the 3

As the author of this stuff, I am fine with any of the 3 as well, with
a very slight bias towards the HAVE_THREADS solution.

>
> [...]
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