3rdparty/ext_ffmpeg/0002-ffmpeg-Fix-crashes-in-ff_seek_frame_binary-if-built-with-la.patch

0001 From eb3a284b4cebfa56eaa11523ebd943fb131b7ea1 Mon Sep 17 00:00:00 2001
0002 From: Dmitry Kazakov <dimula73@gmail.com>
0003 Date: Tue, 11 Apr 2023 11:02:21 +0200
0004 Subject: [PATCH 2/3] -Fix crashes in ff_seek_frame_binary if built with latest
0005  Clang 14
0006
0007 Passing an uninitialized variable as argument to a function is
0008 undefined behaviour (UB). The compiler can assume that UB does not
0009 happen.
0010
0011 Hence, the compiler can assume that the variables are never
0012 uninitialized when passed as argument, which means that the codepaths
0013 that initializes them must be taken.
0014
0015 In ff_seek_frame_binary, this means that the compiler can assume
0016 that the codepaths that initialize pos_min and pos_max are taken,
0017 which means that the conditions "if (sti->index_entries)" and
0018 "if (index >= 0)" can be optimized out.
0019
0020 Current Clang git versions (upcoming Clang 14) enabled an optimization
0021 that does this, which broke the current version of this function
0022 (which intentionally left the variables uninitialized, but silencing
0023 warnings about being uninitialized). See [1] for discussion on
0024 the matter.
0025
0026 [1] https://reviews.llvm.org/D105169#3069555
0027
0028 Original commit:
0029
0030 https://github.com/FFmpeg/FFmpeg/commit/ab792634197e364ca1bb194f9abe36836e42f12d
0031
0032 ---
0033  libavformat/utils.c | 2 +-
0034  1 file changed, 1 insertion(+), 1 deletion(-)
0035
0036 diff --git a/libavformat/utils.c b/libavformat/utils.c
0037 index b2d011a0db..d79a13ca7a 100644
0038 --- a/libavformat/utils.c
0039 +++ b/libavformat/utils.c
0040 @@ -2146,7 +2146,7 @@ int ff_seek_frame_binary(AVFormatContext *s, int stream_index,
0041                           int64_t target_ts, int flags)
0042  {
0043      const AVInputFormat *avif = s->iformat;
0044 -    int64_t av_uninit(pos_min), av_uninit(pos_max), pos, pos_limit;
0045 +    int64_t pos_min = 0, pos_max = 0, pos, pos_limit;
0046      int64_t ts_min, ts_max, ts;
0047      int index;
0048      int64_t ret;
0049 --
0050 2.40.1.windows.1
0051