[FFmpeg-devel] [PATCH 1/4] swr: convert resample_common/linear_int16_mmx2/sse2 to yasm.

[Timothy Gu]

On Jul 12, 2014 11:15 AM, "Andreas Cadhalpun" <
andreas.cadhalpun at googlemail.com> wrote:
>
> On 12.07.2014 19:37, Michael Niedermayer wrote:
>>
>> On Sat, Jul 12, 2014 at 06:58:49PM +0200, Andreas Cadhalpun wrote:
>>>
>>> On 12.07.2014 18:46, Michael Niedermayer wrote:
>>>>
>>>> On Sat, Jul 12, 2014 at 05:35:12PM +0200, Hendrik Leppkes wrote:
>>>>>
>>>>> On Sat, Jul 12, 2014 at 4:45 PM, Andreas Cadhalpun
>>>>> <andreas.cadhalpun at googlemail.com> wrote:
>>>>>>
>>>>>> On 12.07.2014 15:40, Ronald S. Bultje wrote:
>>>>>>>
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> On Sat, Jul 12, 2014 at 9:35 AM, Andreas Cadhalpun <
>>>>>>> andreas.cadhalpun at googlemail.com> wrote:
>>>>>>>
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> I'm a bit puzzled by this commit.
>>>>>>>>
>>>>>>>>
>>>>>>>> On 30.06.2014 01:19, James Almer wrote:
>>>>>>>>
>>>>>>>>> From: Ronald S. Bultje <rsbultje at gmail.com>
>>>>>>>>>
>>>>>>>>> ---
>>>>>>>>>     libswresample/resample_template.c    |  23 +---
>>>>>>>>>     libswresample/x86/resample.asm       | 225
>>>>>>>>> ++++++++++++++++++++++++++---------
>>>>>>>>>     libswresample/x86/resample_mmx.h     | 110 -----------------
>>>>>>>>>     libswresample/x86/resample_x86_dsp.c |  44 +++----
>>>>>>>>>     4 files changed, 187 insertions(+), 215 deletions(-)
>>>>>>>>>
>>>>>>>> [...]
>>>>>>>>
>>>>>>>>    diff --git a/libswresample/x86/resample_mmx.h
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> b/libswresample/x86/resample_mmx.h
>>>>>>>>> index 94237b0..b0ea496 100644
>>>>>>>>> --- a/libswresample/x86/resample_mmx.h
>>>>>>>>> +++ b/libswresample/x86/resample_mmx.h
>>>>>>>>> @@ -22,116 +22,6 @@
>>>>>>>>>     #include "libavutil/cpu.h"
>>>>>>>>>     #include "libswresample/swresample_internal.h"
>>>>>>>>>
>>>>>>>>> -DECLARE_ALIGNED(16, const uint64_t,
ff_resample_int16_rounder)[2]    =
>>>>>>>>> {
>>>>>>>>> 0x0000000000004000ULL, 0x0000000000000000ULL};
>>>>>>>>>
>>>>>>>>
>>>>>>>> This removes the symbol ff_resample_int16_rounder from
libswresample,
>>>>>>>> which is a backwards incompatible ABI change.
>>>>>>>>
>>>>>>>> So can someone explain to me, why this hasn't been accompanied by
a major
>>>>>>>> SOVERSION bump of libswresample?
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> All ff_* symbols are internal.
>>>>>>
>>>>>>
>>>>>>
>>>>>> Then shouldn't all of them be declared with something like
'__attribute__
>>>>>> ((visibility ("hidden")))'?
>>>>>>
>>>>>
>>>>> This is usually handled by a visibility file (.v), but for some reason
>>>>> the swresample file doesn't hide ff_* symbols, but that doesn't really
>>>>> change the fact that ff_* (and avpriv_*) are not part of the public
>>>>> API/ABI and as such any changes or removals do not require a SONAME
>>>>> bump.
>>>>>
>>>>
>>>>> For the reason why they are not hidden, maybe Michael can comment.
>>>>
>>>>
>>>> i assume this was just a copy and paste error, removed ff_* from
>>>> swr
>>>
>>>
>>> So should ff_* also be removed from libavutil.v?
>>
>>
>> yes, but there is some chance that it might break some app so ill
>> wait till after the release
>
>
> Yes, for example this breaks libavfilter:
> undefined reference to `ff_opencl_set_parameter'

This means that the function should probably be avpriv_.

>
>
>>> And what about avpriv_* in libavcodec, libavformat and libavutil?
>>
>>
>> avpriv is shared between the libs so it has to be exported by each
>> lib
>
>
> So avpriv_* symbols shouldn't be removed without SONAME bump (in contrast
to what Hendrik wrote)?

What Hendrik wrote was about ff_, which *can* be removed without MAJOR
bump. You are right about avpriv_.

So, ff_ = can only be used within this library (in theory) and can be
removed without major bump. It should not be exported or be used by users.

avpriv_ = can only be used by FFmpeg libraries and cannot be removed
without major bump. It should be exported, but should not be used by users.

Other av* = can be used by everyone, and are exported and have proper
prototypes or declarations in headers.

Right now, some libraries export some ff_ symbols as hacks and should be
fixed by either converting them to avpriv_ or av_. libavutil exports all
ff_ symbols until the next bump.

Timothy

Timothy