Bug 425469

git bisect points to 8bcf9255d00a28b6abad13023fa2703c78db371a - but it needs 4b0c2e60c70d8ebae87321e4f9ddd8b3876ace03 to get kmix compiled

reverting this code fixes the crash

-                                        char devnum[64];
-                                        snprintf(devnum, sizeof(devnum), "%lu", (unsigned long) dev.index);
-                                        ca_context_change_device(s_ccontext, devnum);
+                                        const QByteArray devnum = QByteArray::number(dev.index);
+                                        ca_context_change_device(s_ccontext, devnum.constData());

(In reply to Jim Jones from comment #2)
> reverting this code fixes the crash
> 
> -                                        char devnum[64];
> -                                        snprintf(devnum, sizeof(devnum),
> "%lu", (unsigned long) dev.index);
> -                                       
> ca_context_change_device(s_ccontext, devnum);
> +                                        const QByteArray devnum =
> QByteArray::number(dev.index);
> +                                       
> ca_context_change_device(s_ccontext, devnum.constData());

this isn't responsible for the crash

seems e20ad13fa703aaba34e23502a912c0c127b0d3d1 is responsible as reverting 8bcf9255d00a28b6abad13023fa2703c78db371a doesn't fix the crash. e20ad13fa703aaba34e23502a912c0c127b0d3d1 + 4b0c2e60c70d8ebae87321e4f9ddd8b3876ace03 to be correct

verified, reverting e20ad13fa703aaba34e23502a912c0c127b0d3d1 + 4b0c2e60c70d8ebae87321e4f9ddd8b3876ace03 fixes the crash

@Jim Jones: many thanks for investigating with bisection, do you have a backtrace?

no, gdb doesn't show anything meaningful. I guess it's because of the self implemented QtPaMainLoop which seems to miss something/does something wrong

Can reproduce (with PulseAudio):

Thread 1 "kmix" received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) where
#0  0x0000000000000000 in ?? ()
#1  0x00007fffee4d2ee9 in pa_srbchannel_free () from /usr/lib64/pulseaudio/libpulsecommon-13.0.so
#2  0x00007fffee4cfb12 in ?? () from /usr/lib64/pulseaudio/libpulsecommon-13.0.so
#3  0x00007fffee4d1dea in pa_pstream_unlink () from /usr/lib64/pulseaudio/libpulsecommon-13.0.so
#4  0x00007ffff2731f15 in ?? () from /usr/lib64/libpulse.so.0
#5  0x00007ffff2732062 in ?? () from /usr/lib64/libpulse.so.0
#6  0x00007ffff7db291d in Mixer_PULSE::~Mixer_PULSE (this=0x5555557e1830, __in_chrg=<optimized out>)
    at kmix/backends/mixer_pulse.cpp:1073
#7  0x00007ffff7db2939 in Mixer_PULSE::~Mixer_PULSE (this=0x5555557e1830, __in_chrg=<optimized out>)
    at kmix/backends/mixer_pulse.cpp:1056
#8  0x00007ffff7d85c16 in Mixer::~Mixer (this=0x55555585a9d0, __in_chrg=<optimized out>)
    at kmix/core/mixer.cpp:115
#9  0x00007ffff7d85c99 in Mixer::~Mixer (this=0x55555585a9d0, __in_chrg=<optimized out>)
    at kmix/core/mixer.cpp:112
#10 0x00007ffff7d7d31a in MixerToolBox::deinitMixer ()
    at kmix/core/mixertoolbox.cpp:356
#11 0x000055555557b978 in KMixWindow::~KMixWindow (this=this@entry=0x555555680970, 
    __in_chrg=<optimized out>, __vtt_parm=<optimized out>)
    at kmix/apps/kmix.cpp:139
#12 0x000055555557bb59 in KMixWindow::~KMixWindow (this=0x555555680970, __in_chrg=<optimized out>, 
    __vtt_parm=<optimized out>) at kmix/apps/kmix.cpp:124
#13 0x0000555555586a76 in KMixApp::~KMixApp (this=0x7fffffffd3d0, __in_chrg=<optimized out>)
    at kmix/apps/KMixApp.cpp:58
#14 0x000055555557850a in main (argc=<optimized out>, argv=<optimized out>)
    at kmix/apps/main.cpp:87
(gdb)

Git commit b3fe63796dfaa0b667c21160a9c10615d6690411 by Jonathan Marten.
Committed on 22/08/2020 at 14:15.
Pushed by marten into branch 'master'.

Mixer: Delay the deletion of the backend

The immediate deletion caused a crash with PulseAudio and
the replacement Qt mainloop.

M  +1    -1    core/mixer.cpp

https://invent.kde.org/multimedia/kmix/commit/b3fe63796dfaa0b667c21160a9c10615d6690411

The previous commit fixes the problem for me, although I'm not sure of the root cause.
If you can compile from source or apply the patch, please test and reopen the bug if the segfault still happens.

*** Bug 425686 has been marked as a duplicate of this bug. ***

*** Bug 425756 has been marked as a duplicate of this bug. ***

Any reason the fix wasn't pushed to 20.08?

For your information I still have the bug despite kmix 20.08.2-2 version.

I use archlinux, I have 2 soundcards installed on my system :

- sound card from the motherboard gigabyte GA-P35-DS3L  : Realtek ALC888
- Yamaha Corporation YMF-744B [DS-1S Audio Controller] (rev 02)

Not sure if it's the same bug, here is my original bug report from august 2020 about kmixctrl component :
https://bugs.kde.org/show_bug.cgi?id=425686

at each startup I see this error on dmesg :
kmixctrl[766]: segfault at 0 ip 0000000000000000 sp 00007fff8c7d4418 error 14 in kmixctrl[5617ae3ba000+2000]

despite the segfault kmix is still running fine on background

Hello,

with the new version kmix 20.08.2-2 it is ok the bug is gone,

thanks

with kmix 20.08.3-1 the bug is back again.

I confirm that the bug is back again with kmix 20.08.3-1