On 7/19/24 12:56 PM, Stephen Hutchinson wrote:
The atexit() handler in the avisynth demuxer was added because
there was a conflict in AvxSynth that arose due to their use
of C++ global objects, particularly in relation to having
added a logging function relying on log4cpp.
This conflict was responsible for causing a segfault on exit.
It did not affect Windows with the (at the time) upstream
AviSynth 2.5 and 2.6, nor does it affect AviSynth+.
Unfortunately, none of this was actually shielded by ifdefs
indicating the fact it was only needed for AvxSynth, so four
years ago when AviSynth+ replaced AvxSynth as the handler
for AviSynth scripts on Unix-like OSes, the fact that the
atexit handler was no longer necessary was overlooked.
Signed-off-by: Stephen Hutchinson <qyo...@gmail.com>
---
Changes compared to v1:
* Added missing dlclose invocation to read_close
libavformat/avisynth.c | 46 +-----------------------------------------
1 file changed, 1 insertion(+), 45 deletions(-)
diff --git a/libavformat/avisynth.c b/libavformat/avisynth.c
index 625bdf7e3a..26747671c0 100644
--- a/libavformat/avisynth.c
+++ b/libavformat/avisynth.c
@@ -115,9 +115,6 @@ typedef struct AviSynthContext {
int error;
uint32_t flags;
-
- /* Linked list pointers. */
- struct AviSynthContext *next;
} AviSynthContext;
static const int avs_planes_packed[1] = { 0 };
@@ -133,15 +130,7 @@ static const int avs_planes_rgba[4] = { AVS_PLANAR_G,
AVS_PLANAR_B,
static AVMutex avisynth_mutex = AV_MUTEX_INITIALIZER;
-/* A conflict between C++ global objects, atexit, and dynamic loading requires
- * us to register our own atexit handler to prevent double freeing. */
static AviSynthLibrary avs_library;
-static int avs_atexit_called = 0;
-
-/* Linked list of AviSynthContexts. An atexit handler destroys this list. */
-static AviSynthContext *avs_ctx_list = NULL;
-
-static av_cold void avisynth_atexit_handler(void);
static av_cold int avisynth_load_library(void)
{
@@ -185,7 +174,6 @@ static av_cold int avisynth_load_library(void)
LOAD_AVS_FUNC(avs_get_env_property, 1);
#undef LOAD_AVS_FUNC
- atexit(avisynth_atexit_handler);
return 0;
fail:
@@ -214,30 +202,11 @@ static av_cold int
avisynth_context_create(AVFormatContext *s)
}
}
- if (!avs_ctx_list) {
- avs_ctx_list = avs;
- } else {
- avs->next = avs_ctx_list;
- avs_ctx_list = avs;
- }
-
return 0;
}
static av_cold void avisynth_context_destroy(AviSynthContext *avs)
{
- if (avs_atexit_called)
- return;
-
- if (avs == avs_ctx_list) {
- avs_ctx_list = avs->next;
- } else {
- AviSynthContext *prev = avs_ctx_list;
- while (prev->next != avs)
- prev = prev->next;
- prev->next = avs->next;
- }
-
if (avs->clip) {
avs_library.avs_release_clip(avs->clip);
avs->clip = NULL;
@@ -248,20 +217,6 @@ static av_cold void
avisynth_context_destroy(AviSynthContext *avs)
}
}
-static av_cold void avisynth_atexit_handler(void)
-{
- AviSynthContext *avs = avs_ctx_list;
-
- while (avs) {
- AviSynthContext *next = avs->next;
- avisynth_context_destroy(avs);
- avs = next;
- }
- dlclose(avs_library.library);
-
- avs_atexit_called = 1;
-}
-
/* Create AVStream from audio and video data. */
static int avisynth_create_stream_video(AVFormatContext *s, AVStream *st)
{
@@ -1134,6 +1089,7 @@ static av_cold int avisynth_read_close(AVFormatContext *s)
return AVERROR_UNKNOWN;
avisynth_context_destroy(s->priv_data);
+ dlclose(avs_library.library);
ff_mutex_unlock(&avisynth_mutex);
return 0;
}
Pushed.
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