[Bug] Nheko immediate crash when run (actually libavcodec/libx265 related)

[d-musique]

OpenMandriva version:
OpenMandriva Lx release 25.90 (Nickel) Cooker for znver1

Describe the bug:
Nheko segfaults and prints a stack trace involving libavcodec.

Steps to reproduce:
Run nheko in a terminal.
It's probably needed to enable the restricted repo and install lib64x265 from there.

Observed behavior:

Running nheko directly shows the following output

[2025-11-28 11:04:31.515] [qml] [info] Using Qt multimedia with FFmpeg version 8.0.1 nonfree and unredistributable (:0, )
Error: signal 11:
nheko(+0xaf4fa5) [0x5638da1defa5]
/lib64/libc.so.6(+0x40850) [0x7fe222c49850]
/lib64/libavcodec.so.62(+0xb148c0) [0x7fe1d5f148c0]
/lib64/libavcodec.so.62(avcodec_get_supported_config+0x41) [0x7fe1d59e2ee1]
/usr/lib64/qt6/plugins/multimedia/libffmpegmediaplugin.so(+0x37f12) [0x7fe1e458af12]
/usr/lib64/qt6/plugins/multimedia/libffmpegmediaplugin.so(+0x37829) [0x7fe1e458a829]
/usr/lib64/qt6/plugins/multimedia/libffmpegmediaplugin.so(+0x3336e) [0x7fe1e458636e]
/usr/lib64/qt6/lib/libQt6Multimedia.so.6(+0xf8e94) [0x7fe2256c7e94]
/usr/lib64/qt6/lib/libQt6Multimedia.so.6(+0xf8b26) [0x7fe2256c7b26]
/usr/lib64/qt6/lib/libQt6Multimedia.so.6(_ZN12QMediaPlayerC1EP7QObject+0x105) [0x7fe2256ce9d5]
nheko(+0x9cbc7d) [0x5638da0b5c7d]
nheko(+0xaf974c) [0x5638da1e374c]
/lib64/libc.so.6(+0x2acf5) [0x7fe222c33cf5]
/lib64/libc.so.6(__libc_start_main+0x87) [0x7fe222c33da7]
nheko(+0x62e2f1) [0x5638d9d182f1]

Additional comment:

The problem happens during the static initialization of ffmpeg codecs.

The stack trace stops at the call site of a libx265 function which valgrind designates as "invalid address".
libx265 is a library which openmandriva loads at runtime, by a custom ffmpeg patch.

Perhaps here is a good place to start looking
https://github.com/OpenMandrivaAssociation/ffmpeg/blob/master/ffmpeg-4.3-dlopen-faac-mp3lame-opencore-x264-x265-xvid.patch

libavcodec refers to revision 215 of libx265, which is indeed the installed version.

Logs and screenshots if relevant

gdb

[2025-11-28 11:09:37.488] [qml] [info] Using Qt multimedia with FFmpeg version 8.0.1 nonfree and unredistributable (:0, )

Thread 1 "nheko" received signal SIGSEGV, Segmentation fault.
0x00007fffa73148c0 in libx265_get_supported_config (avctx=<optimized out>, codec=0x7fffa79e5340 <ff_libx265_encoder>, config=AV_CODEC_CONFIG_PIX_FORMAT,
    flags=<optimized out>, out=0x7fffffffc970, out_num=0x7fffffffc998) at libavcodec/libx265.c:1034
1034            if (x265_api_get(12)) {
(gdb) bt
#0  0x00007fffa73148c0 in libx265_get_supported_config (avctx=<optimized out>, codec=0x7fffa79e5340 <ff_libx265_encoder>, config=AV_CODEC_CONFIG_PIX_FORMAT,
    flags=<optimized out>, out=0x7fffffffc970, out_num=0x7fffffffc998) at libavcodec/libx265.c:1034
#1  0x00007fffa6de2ee1 in avcodec_get_supported_config (avctx=0xc, codec=0x7fffa79e5340 <ff_libx265_encoder>, config=AV_CODEC_CONFIG_PIX_FORMAT, flags=0,
    out=0x7fffffffc970, out_num=0x0) at libavcodec/avcodec.c:806
#2  0x00007fffd00d8f12 in QFFmpeg::deviceTypes()::$_0::operator()() const () from /usr/lib64/qt6/plugins/multimedia/libffmpegmediaplugin.so
#3  0x00007fffd00d8829 in QFFmpeg::deviceTypes(char const*) () from /usr/lib64/qt6/plugins/multimedia/libffmpegmediaplugin.so
#4  0x00007fffd00d436e in QFFmpegMediaPlugin::create(QString const&) () from /usr/lib64/qt6/plugins/multimedia/libffmpegmediaplugin.so
#5  0x00007ffff70c7e94 in (anonymous namespace)::InstanceHolder::init() () from /usr/lib64/qt6/lib/libQt6Multimedia.so.6
#6  0x00007ffff70c7b26 in QGlobalStatic<QtGlobalStatic::ApplicationHolder<(anonymous namespace)::(anonymous namespace)::Q_QAS_s_instanceHolder> >::operator->() ()
   from /usr/lib64/qt6/lib/libQt6Multimedia.so.6
#7  0x00007ffff70ce9d5 in QMediaPlayer::QMediaPlayer(QObject*) () from /usr/lib64/qt6/lib/libQt6Multimedia.so.6
#8  0x0000555555f1fc7d in ChatPage::ChatPage(QSharedPointer<UserSettings>, QObject*) ()
#9  0x000055555604d74c in main ()

valgrind

==417107== Jump to the invalid address stated on the next line
==417107==    at 0x22B40476BC602C22: ???
==417107==    by 0x3882D8C5: libx265_get_supported_config (libx265.c:1034)
==417107==    by 0x382A1C7A: av_codec_init_static (allcodecs.c:953)
==417107==    by 0x8B35905: __pthread_once_slow.isra.0 (in /usr/lib64/libc.so.6)
==417107==    by 0x8B35978: pthread_once@@GLIBC_2.34 (in /usr/lib64/libc.so.6)
==417107==    by 0x382A1B6A: av_codec_iterate (allcodecs.c:984)
==417107==    by 0x326F2E92: ??? (in /usr/lib64/qt6/plugins/multimedia/libffmpegmediaplugin.so)
==417107==    by 0x326F2828: ??? (in /usr/lib64/qt6/plugins/multimedia/libffmpegmediaplugin.so)
==417107==    by 0x326EE36D: ??? (in /usr/lib64/qt6/plugins/multimedia/libffmpegmediaplugin.so)
==417107==    by 0x63C2E93: ??? (in /usr/lib64/qt6/lib/libQt6Multimedia.so.6.10.1)
==417107==    by 0x63C2B25: ??? (in /usr/lib64/qt6/lib/libQt6Multimedia.so.6.10.1)
==417107==    by 0x63C99D4: QMediaPlayer::QMediaPlayer(QObject*) (in /usr/lib64/qt6/lib/libQt6Multimedia.so.6.10.1)
==417107==  Address 0x22b40476bc602c22 is not stack'd, malloc'd or (recently) free'd

[d-musique]

I believe to have partially identified a problem in the patch ffmpeg-4.3-dlopen-faac-mp3lame-opencore-x264-x265-xvid.patch.

On the first entry to loadLibX265, we would expect the value of dl_x265_api_get to be NULL but it isn't.

I have loadLibX265 (1) 0xc77eed0f5e3fca55.

x265_api_func dl_x265_api_get = NULL;
#define x265_api_get dl_x265_api_get

static int loadLibX265();
static int loadLibX265() {
    /* fprintf(stderr, "loadLibX265 (1) %p\n", (void *)dl_x265_api_get); */
    if (dl_x265_api_get)
        return 0;

[ZeroAbility]

Run nheko in a terminal.
It's probably needed to enable the restricted repo and install lib64x265 from there.

I have these conditions also and I do not get this error.

[d-musique]

Edited: Today I have a crash with a different trace than above.
Minimal code below is a simple repro which used to crash the library.

❯ clang -O2 -g -o av_codec_iterate av_codec_iterate.c -lavcodec && ./av_codec_iterate
zsh: segmentation fault (core dumped)  ./av_codec_iterate

This crash is it's a heisenbug, I don't myself get always get the exact same effect or repro at 100% certainty.

Having spent over a hour in gdb and valgrind debugging the last time over this error, i was not able to identify the origin of the problem. What I can simply tell is by rebuilding the ffmpeg package without dlopen patches, it works without problems.

---

av_codec_iterate.c

#include <libavcodec/codec.h>

int main()
{
    void *iter = NULL;
    av_codec_iterate(&iter);
    return 0;
}

[ZeroAbility]

You have requested a lot of things pertaining to audio. Have you made any modifications (such as compiling your own sources) that could lead to the issue? Does this happen with other applications that use the library?

[d-musique]

Previous post erratum: the test code was rewritten this morning in a rush, was faulty, so I edited it, and the crash was falsely related.

However, this minimal code (correctly written) was able to trigger the ffmpeg bug 3 weeks ago.
At this time, I don't have repro of the original problem, neither in nheko or other program.

If you want, the bug can be closed and reopened if I hit it another time later...

Have you made any modifications (such as compiling your own sources) that could lead to the issue?

None, and I don't have a specialized audio workflow on this machine.

[ZeroAbility]

If you want, the bug can be closed and reopened if I hit it another time later...

Since it can't be reproduced, you will need to check the upstream Issues for reports.