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

[wm4]

On Mon, 17 Apr 2017 12:06:59 -0300
James Almer <jamrial at gmail.com> 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).

Better solution: move all the code to a .c file.