[FFmpeg-trac] #9986(avutil:new): Compilation error [-Wincompatible-pointer-types] on AOSP for x86 (32bits)

[FFmpeg]

#9986: Compilation error [-Wincompatible-pointer-types] on AOSP for x86 (32bits)
-------------------------------------+----------------------------------
             Reporter:  goffioul     |                    Owner:  (none)
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:  avutil
              Version:  unspecified  |               Resolution:
             Keywords:  vaapi        |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+----------------------------------
Comment (by goffioul):

 Please learn that the extra compilation flags were just a mean to an end,
 to reach a similar situation as when building within AOSP. The issue was
 detected with Android, but it's actually a generic incompatible pointer
 assignment problem, so I provided a simpler way for you to trigger the
 compilation error.

 The variable `buffer_handle` is declared with type `unsigned long`. Its
 address is then assigned to a `uintptr_t *` field member. This trigger the
 Wincompatible-pointer-types warning in both gcc and clang, and a
 compilation error when using Werror.

 To answer your question about using --disable-vaapi, obviously the
 original compilation error will disappear, as the corresponding file is
 not compiled in. It's a no-brainer. However, compilation still fails, but
 only with gcc, with this error:

 {{{
 src/libavutil/timecode.c: In function ‘av_timecode_make_string’:
 src/libavutil/timecode.c:123:60: error: ‘%0*d’ directive output may be
 truncated writing between 1 and 10 bytes into a region of size between 2
 and 14 [-Werror=format-truncation=]
   123 |     snprintf(buf, AV_TIMECODE_STR_SIZE, "%s%02d:%02d:%02d%c%0*d",
       |                                                            ^~~~
 src/libavutil/timecode.c:123:41: note: directive argument in the range [0,
 2147483647]
   123 |     snprintf(buf, AV_TIMECODE_STR_SIZE, "%s%02d:%02d:%02d%c%0*d",
       |                                         ^~~~~~~~~~~~~~~~~~~~~~~~
 src/libavutil/timecode.c:123:5: note: ‘snprintf’ output between 11 and 32
 bytes into a destination of size 23
   123 |     snprintf(buf, AV_TIMECODE_STR_SIZE, "%s%02d:%02d:%02d%c%0*d",
       |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   124 |              neg ? "-" : "",
       |              ~~~~~~~~~~~~~~~
   125 |              hh, mm, ss, drop ? ';' : ':', ff_len, ff);
       |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 CC      libavutil/tx.o
 cc1: some warnings being treated as errors
 }}}

 This can be worked around by using `--extra-cflags=-Wno-format-
 truncation`, in which case ffmpeg compilation succeeds. This is however
 specific to gcc, as to my knowledge clang does not have Wformat-truncation
 warning. Hence, this specific error does not pop up with AOSP.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9986#comment:4>
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