[FFmpeg-devel] [PATCH 1/4] lavc/parser: use C11 atomics

[Hendrik Leppkes]

On Thu, Nov 30, 2017 at 3:17 PM, Michael Niedermayer
<michael at niedermayer.cc> wrote:
> On Thu, Nov 30, 2017 at 11:55:03AM +0000, Rostislav Pehlivanov wrote:
>> On 28 November 2017 at 01:26, Michael Niedermayer <michael at niedermayer.cc>
>> wrote:
>>
>> > On Mon, Nov 27, 2017 at 04:30:18AM +0000, Rostislav Pehlivanov wrote:
>> > > Signed-off-by: Rostislav Pehlivanov <atomnuker at gmail.com>
>> > > ---
>> > >  libavcodec/parser.c | 14 ++++++++------
>> > >  1 file changed, 8 insertions(+), 6 deletions(-)
>> > >
>> > > diff --git a/libavcodec/parser.c b/libavcodec/parser.c
>> > > index 670680ea7c..baf1de4d88 100644
>> > > --- a/libavcodec/parser.c
>> > > +++ b/libavcodec/parser.c
>> > > @@ -23,30 +23,32 @@
>> > >  #include <inttypes.h>
>> > >  #include <stdint.h>
>> > >  #include <string.h>
>> > > +#include <stdatomic.h>
>> > >
>> > >  #include "libavutil/avassert.h"
>> > > -#include "libavutil/atomic.h"
>> > >  #include "libavutil/internal.h"
>> > >  #include "libavutil/mem.h"
>> > >
>> > >  #include "internal.h"
>> > >  #include "parser.h"
>> > >
>> > > -static AVCodecParser *av_first_parser = NULL;
>> > > +static _Atomic(AVCodecParser *)av_first_parser = NULL;
>> >
>> > This doesnt build here
>> >
>> > libavcodec/parser.c:35:8: warning: return type defaults to ‘int’ [enabled
>> > by default]
>> >  static _Atomic(AVCodecParser *)av_first_parser = NULL;
>> >         ^
>> > libavcodec/parser.c: In function ‘_Atomic’:
>> > libavcodec/parser.c:35:32: error: expected declaration specifiers before
>> > ‘av_first_parser’
>> >  static _Atomic(AVCodecParser *)av_first_parser = NULL;
>> >                                 ^
>> > libavcodec/parser.c:38:1: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or
>> > ‘__attribute__’ before ‘{’ token
>> >  {
>> >  ^
>> > libavcodec/parser.c:46:1: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or
>> > ‘__attribute__’ before ‘{’ token
>> >  {
>> >  ^
>> > libavcodec/parser.c:55:1: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__a
>> >
>> >
>> > [...]
>> > --
>> > Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>> >
>> > Observe your enemies, for they first find out your faults. -- Antisthenes
>> >
>> > _______________________________________________
>> > ffmpeg-devel mailing list
>> > ffmpeg-devel at ffmpeg.org
>> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>> >
>> >
>>
>> Does the attached patch work?
>
>>  parser.c |   14 ++++++++------
>>  1 file changed, 8 insertions(+), 6 deletions(-)
>> 71f66a37fb46e29626f27da4658f34927e48033c  v2-0001-lavc-parser-use-C11-atomics.patch
>> From b9ed59e9aff4a0fcc40f444f307c87acad55e139 Mon Sep 17 00:00:00 2001
>> From: Rostislav Pehlivanov <atomnuker at gmail.com>
>> Date: Mon, 27 Nov 2017 01:56:41 +0000
>> Subject: [PATCH v2 1/2] lavc/parser: use C11 atomics
>>
>> Signed-off-by: Rostislav Pehlivanov <atomnuker at gmail.com>
>> ---
>>  libavcodec/parser.c | 14 ++++++++------
>>  1 file changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/libavcodec/parser.c b/libavcodec/parser.c
>> index 670680ea7c..d6df62bf70 100644
>> --- a/libavcodec/parser.c
>> +++ b/libavcodec/parser.c
>> @@ -23,30 +23,32 @@
>>  #include <inttypes.h>
>>  #include <stdint.h>
>>  #include <string.h>
>> +#include <stdatomic.h>
>>
>>  #include "libavutil/avassert.h"
>> -#include "libavutil/atomic.h"
>>  #include "libavutil/internal.h"
>>  #include "libavutil/mem.h"
>>
>>  #include "internal.h"
>>  #include "parser.h"
>>
>> -static AVCodecParser *av_first_parser = NULL;
>> +static _Atomic(AVCodecParser *) av_first_parser = NULL;
>
> no
>
>
> libavcodec/parser.c:35:8: warning: return type defaults to ‘int’ [enabled by default]
>  static _Atomic(AVCodecParser *) av_first_parser = NULL;
>         ^
> libavcodec/parser.c: In function ‘_Atomic’:
> libavcodec/parser.c:35:33: error: expected declaration specifiers before ‘av_first_parser’
>  static _Atomic(AVCodecParser *) av_first_parser = NULL;
>
> also see
> compat/atomics/gcc/stdatomic.h
>
> i think what you do is not supportd in that
>
>

_Atomic is a keywork like volatile, so its syntax should be the same.
Perhaps those emulations should just define it to "volatile" if its
missing - the win32 emulation certainly would expect it to be
volatile, and I would expect this to be true for the others as well.

- Hendrik