[FFmpeg-devel] libavutil/thread.h: Fixed g++ build error when ASSERT_LEVEL is greater than 1

[Aaron Levinson]

On 4/19/2017 2:27 PM, Marton Balint wrote:
>
> On Mon, 17 Apr 2017, James Almer wrote:
>
>> On 4/17/2017 5:39 AM, Clément Bœsch wrote:
>>> On Sun, Apr 16, 2017 at 05:20:02PM -0700, Aaron Levinson wrote:
>>>> From 9e6a9e2b8d58f17c661a3f455e03c95587ec7b18 Mon Sep 17 00:00:00 2001
>>>> From: Aaron Levinson <alevinsn at aracnet.com>
>>>> Date: Sun, 16 Apr 2017 17:13:31 -0700
>>>> Subject: [PATCH] libavutil/thread.h:  Fixed g++ build error when
>>>>  ASSERT_LEVEL is greater than 1
>>>>
>>>> Purpose: libavutil/thread.h: Fixed g++ build error when ASSERT_LEVEL
>>>> is greater than 1.  This is only relevant when thread.h is included by
>>>> C++ files.  In this case, the relevant code is only defined if
>>>> HAVE_PTHREADS is defined as 1.  Use configure --assert-level=2 to do
>>>> so.
>>>>
>>>> Note: Issue discovered as a result of Coverity build failure.  Cause
>>>> of build failure pinpointed by Hendrik Leppkes.
>>>>
>>>> Comments:
>>>>
>>>> -- libavutil/thread.h: Altered ASSERT_PTHREAD_NORET definition such
>>>>    that it uses av_make_error_string instead of av_err2str().
>>>>    av_err2str() uses a "parenthesized type followed by an initializer
>>>>    list", which is apparently not valid C++.  This issue started
>>>>    occurring because thread.h is now included by the DeckLink C++
>>>>    files.  The alteration does the equivalent of what av_err2str()
>>>>    does, but instead declares the character buffer as a local
>>>>    variable.
>>>> ---
>>>>  libavutil/thread.h | 5 ++++-
>>>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/libavutil/thread.h b/libavutil/thread.h
>>>> index 6e57447..f108e20 100644
>>>> --- a/libavutil/thread.h
>>>> +++ b/libavutil/thread.h
>>>> @@ -36,8 +36,11 @@
>>>>  #define ASSERT_PTHREAD_NORET(func, ...) do
>>>> {                            \
>>>>      int ret =
>>>> func(__VA_ARGS__);                                        \
>>>>      if (ret)
>>>> {                                                          \
>>>> +        char errbuf[AV_ERROR_MAX_STRING_SIZE] =
>>>> "";                     \
>>>>          av_log(NULL, AV_LOG_FATAL,
>>>> AV_STRINGIFY(func)                   \
>>>> -               " failed with error: %s\n",
>>>> av_err2str(AVERROR(ret)));   \
>>>> +               " failed with error:
>>>> %s\n",                              \
>>>> +               av_make_error_string(errbuf,
>>>> AV_ERROR_MAX_STRING_SIZE,   \
>>>> +
>>>> AVERROR(ret)));                     \
>>>>
>>>> abort();                                                        \
>>>>
>>>> }                                                                   \
>>>>  } while (0)
>>>
>>> I don't like limiting ourselves in the common C code of the project
>>> because C++ is a bad and limited language. Can't you solve this by
>>> bumping
>>> the minimal requirement of C++ version?
>>
>> We're already using C++11 when available because of atomics on
>> mediacodec.
>> Also, just tried and it seems to fail even with C++14, so it just doesn't
>> work with C++.
>>
>> We could instead just make these strict assert wrappers work only on C
>> code by for example checking for defined(__cplusplus).
>
> I'd say let's apply the patch as is, that is the simplest solution.
>
> Regards,
> Marton

I don't think most people care one way or the other--perhaps someone 
with push privileges could apply the patch?  I assume that the Coverity 
builds are continuing to fail as a result of the issue that this patch 
addresses.

Thanks,
Aaron Levinson