[FFmpeg-devel] [PATCH] ffmpeg: remove usage of internal deprecation macro

[James Almer]

On 3/16/2022 10:10 AM, Andreas Rheinhardt wrote:
> James Almer:
>>
>>
>> On 3/16/2022 9:58 AM, Andreas Rheinhardt wrote:
>>> James Almer:
>>>>
>>>>
>>>> On 3/16/2022 7:15 AM, Andreas Rheinhardt wrote:
>>>>> James Almer:
>>>>>> Signed-off-by: James Almer <jamrial at gmail.com>
>>>>>> ---
>>>>>>     fftools/ffmpeg.c | 4 ++--
>>>>>>     1 file changed, 2 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
>>>>>> index a98e49b775..3b625a9918 100644
>>>>>> --- a/fftools/ffmpeg.c
>>>>>> +++ b/fftools/ffmpeg.c
>>>>>> @@ -2880,9 +2880,9 @@ static int init_input_stream(int ist_index,
>>>>>> char *error, int error_len)
>>>>>>             ist->dec_ctx->opaque                = ist;
>>>>>>             ist->dec_ctx->get_format            = get_format;
>>>>>>     #if LIBAVCODEC_VERSION_MAJOR < 60
>>>>>> -FF_DISABLE_DEPRECATION_WARNINGS
>>>>>> +        AV_NOWARN_DEPRECATED({
>>>>>>             ist->dec_ctx->thread_safe_callbacks = 1;
>>>>>> -FF_ENABLE_DEPRECATION_WARNINGS
>>>>>> +        })
>>>>>>     #endif
>>>>>>               if (ist->dec_ctx->codec_id == AV_CODEC_ID_DVB_SUBTITLE &&
>>>>>
>>>>> AV_NOWARN_DEPRECATED currently doesn't work with Clang; so you first
>>>>> need to find out from which version onward it supports these macros.
>>>>
>>>> Does not work in what way? Not compile, or just be a no-op?
>>>> If the latter, then that's a limitation FF_DISABLE_DEPRECATION_WARNINGS
>>>> also has for some targets. We're not going to stop using a macro just
>>>> because it does nothing in some scenarios.
>>>
>>> Clang takes this path in AV_NOWARN_DEPRECATED:
>>> #    define AV_NOWARN_DEPRECATED(code) code
>>> So it is a no-op and the warning is not gone; any recent version of it
>>> will understand the GCC pragma, so this can be rectified.
>>> Looking at our internal deprecation macros shows that it is possible to
>>> also support the Intel compiler.
>>> And I really don't like that you are basically declaring Clang to be
>>> irrelevant; it is so important that you should have tested it.
>>
>> I'm not declaring it irrelevant, i'm saying that if a public macro has
>> no implementation for a given compiler, then that's unrelated to its
>> usage. The internal macro also has limitations, yet it hasn't stopped us
>> from using it anywhere.
>>
>> I'm removing the usage of an internal macro from a file that should not
>> access it, and replacing it with a public one. What happens under the
>> hood is a separate issue. Supporting more compilers in
>> AV_NOWARN_DEPRECATED() is a separate fix.
> 
> Separate, but not independent: Supporting more compilers should come first.
> 
> - Andreas

Can you implement it? I don't have a Clang toolchain nor do i know how 
to check for supported Pragmas. defined(__clang__) is probably too broad 
for this.