GTK2+ applications don't start

[cryptomilk]

Hi,

I have problems starting up easytag if qtcurve is in use. I have 1.8.17 here, it works if I use 1.8.16 with the runCommand patch and start it in strace.

[cryptomilk]

strace

(gdb) bt
#0  0x00007ffff4ba60d2 in wait () from /lib64/libc.so.6
#1  0x000000000043674b in ?? ()
#2  <signal handler called>
#3  0x00007ffff4b5a3ac in _IO_proc_close@@GLIBC_2.2.5 () from /lib64/libc.so.6
#4  0x00007ffff4b63b20 in __GI__IO_file_close_it () from /lib64/libc.so.6
#5  0x00007ffff4b58688 in fclose@@GLIBC_2.2.5 () from /lib64/libc.so.6
#6  0x00007fffeaf9ee9a in runCommand () from /usr/lib64/gtk-2.0/2.10.0/engines/libqtcurve.so
#7  0x00007fffeaf9eed4 in ?? () from /usr/lib64/gtk-2.0/2.10.0/engines/libqtcurve.so
#8  0x00007fffeaf9efbe in ?? () from /usr/lib64/gtk-2.0/2.10.0/engines/libqtcurve.so
#9  0x00007fffeaf9f502 in qtSettingsInit () from /usr/lib64/gtk-2.0/2.10.0/engines/libqtcurve.so
#10 0x00007fffeaf9afb3 in ?? () from /usr/lib64/gtk-2.0/2.10.0/engines/libqtcurve.so
#11 0x00007ffff6af5dab in g_type_create_instance () from /usr/lib64/libgobject-2.0.so.0
#12 0x00007ffff6ada275 in ?? () from /usr/lib64/libgobject-2.0.so.0
#13 0x00007ffff6adc06d in g_object_newv () from /usr/lib64/libgobject-2.0.so.0
#14 0x00007ffff6adc81c in g_object_new () from /usr/lib64/libgobject-2.0.so.0
#15 0x00007fffeaf9b78c in theme_create_rc_style () from /usr/lib64/gtk-2.0/2.10.0/engines/libqtcurve.so
#16 0x00007ffff791d906 in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#17 0x00007ffff791e1d5 in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#18 0x00007ffff791e36f in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#19 0x00007ffff791cb68 in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#20 0x00007ffff791e1d5 in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#21 0x00007ffff791e36f in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#22 0x00007ffff791ebdf in gtk_rc_reparse_all_for_settings () from /usr/lib64/libgtk-x11-2.0.so.0
#23 0x00007ffff793ab12 in gtk_settings_get_for_screen () from /usr/lib64/libgtk-x11-2.0.so.0
#24 0x00007fffeb7fae66 in ?? () from /usr/lib64/gtk-2.0/modules/libcanberra-gtk-module.so
#25 0x00007fffeb7fb128 in gtk_module_init () from /usr/lib64/gtk-2.0/modules/libcanberra-gtk-module.so
#26 0x00007ffff78eb441 in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#27 0x00007ffff6ad5318 in g_closure_invoke () from /usr/lib64/libgobject-2.0.so.0
#28 0x00007ffff6ae6cad in ?? () from /usr/lib64/libgobject-2.0.so.0
#29 0x00007ffff6aee9b9 in g_signal_emit_valist () from /usr/lib64/libgobject-2.0.so.0
#30 0x00007ffff6aeec72 in g_signal_emit () from /usr/lib64/libgobject-2.0.so.0
#31 0x00007ffff6ad9695 in ?? () from /usr/lib64/libgobject-2.0.so.0
#32 0x00007ffff6adbc4b in g_object_notify () from /usr/lib64/libgobject-2.0.so.0
#33 0x00007ffff75097b5 in gdk_display_open_default_libgtk_only () from /usr/lib64/libgdk-x11-2.0.so.0
#34 0x00007ffff78d34b4 in gtk_init_check () from /usr/lib64/libgtk-x11-2.0.so.0
#35 0x00007ffff78d34d9 in gtk_init () from /usr/lib64/libgtk-x11-2.0.so.0
#36 0x000000000041140d in ?? ()
#37 0x00007ffff4b0fbe5 in __libc_start_main () from /lib64/libc.so.6
#38 0x0000000000414eed in ?? ()

It hangs in the pclose() in runCommand()

[yuyichao]

Did you get any signal with gdb?
In #2 of your bt it says <signal handler called>.
Also, what's your distribution and glibc/easytag version?

[cryptomilk]

That's my pressing ctrl+c

^C
Program received signal SIGINT, Interrupt.
0x00007ffff4ba60d2 in wait () from /lib64/libc.so.6
(gdb) bt
#0  0x00007ffff4ba60d2 in wait () from /lib64/libc.so.6
#1  0x000000000043674b in ?? ()
#2  <signal handler called>
#3  0x00007ffff4b5a3ac in _IO_proc_close@@GLIBC_2.2.5 () from /lib64/libc.so.6
#4  0x00007ffff4b63b20 in __GI__IO_file_close_it () from /lib64/libc.so.6
#5  0x00007ffff4b58688 in fclose@@GLIBC_2.2.5 () from /lib64/libc.so.6
#6  0x00007fffeaf9ee9a in runCommand (cmd=<optimized out>, result=0x7fffeb1d7be8 <kdeHome.53930>) at /usr/src/debug/qtcurve-1.8.17/gtk2/style/qt_settings.c:2950
#7  0x00007fffeaf9eed4 in getKdeHome () at /usr/src/debug/qtcurve-1.8.17/gtk2/style/qt_settings.c:67
#8  0x00007fffeaf9efbe in kdeFile (f=f@entry=0x7fffeafca8ca "kdeglobals") at /usr/src/debug/qtcurve-1.8.17/gtk2/style/qt_settings.c:101
#9  0x00007fffeaf9f502 in kdeGlobals () at /usr/src/debug/qtcurve-1.8.17/gtk2/style/qt_settings.c:111
#10 qtSettingsInit () at /usr/src/debug/qtcurve-1.8.17/gtk2/style/qt_settings.c:1975
#11 0x00007fffeaf9afb3 in qtcurve_rc_style_init (qtcurve_rc=<optimized out>) at /usr/src/debug/qtcurve-1.8.17/gtk2/style/qtcurve.c:2952
#12 0x00007ffff6af5dab in g_type_create_instance () from /usr/lib64/libgobject-2.0.so.0
#13 0x00007ffff6ada275 in ?? () from /usr/lib64/libgobject-2.0.so.0
#14 0x00007ffff6adc06d in g_object_newv () from /usr/lib64/libgobject-2.0.so.0
#15 0x00007ffff6adc81c in g_object_new () from /usr/lib64/libgobject-2.0.so.0
#16 0x00007fffeaf9b78c in theme_create_rc_style () at /usr/src/debug/qtcurve-1.8.17/gtk2/style/qtcurve.c:3024
#17 0x00007ffff791d906 in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#18 0x00007ffff791e1d5 in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#19 0x00007ffff791e36f in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#20 0x00007ffff791cb68 in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#21 0x00007ffff791e1d5 in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#22 0x00007ffff791e36f in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#23 0x00007ffff791ebdf in gtk_rc_reparse_all_for_settings () from /usr/lib64/libgtk-x11-2.0.so.0
#24 0x00007ffff793ab12 in gtk_settings_get_for_screen () from /usr/lib64/libgtk-x11-2.0.so.0
#25 0x00007fffeb7fae66 in ?? () from /usr/lib64/gtk-2.0/modules/libcanberra-gtk-module.so
#26 0x00007fffeb7fb128 in gtk_module_init () from /usr/lib64/gtk-2.0/modules/libcanberra-gtk-module.so
#27 0x00007ffff78eb441 in ?? () from /usr/lib64/libgtk-x11-2.0.so.0
#28 0x00007ffff6ad5318 in g_closure_invoke () from /usr/lib64/libgobject-2.0.so.0
#29 0x00007ffff6ae6cad in ?? () from /usr/lib64/libgobject-2.0.so.0
#30 0x00007ffff6aee9b9 in g_signal_emit_valist () from /usr/lib64/libgobject-2.0.so.0
#31 0x00007ffff6aeec72 in g_signal_emit () from /usr/lib64/libgobject-2.0.so.0
#32 0x00007ffff6ad9695 in ?? () from /usr/lib64/libgobject-2.0.so.0
#33 0x00007ffff6adbc4b in g_object_notify () from /usr/lib64/libgobject-2.0.so.0
#34 0x00007ffff75097b5 in gdk_display_open_default_libgtk_only () from /usr/lib64/libgdk-x11-2.0.so.0
#35 0x00007ffff78d34b4 in gtk_init_check () from /usr/lib64/libgtk-x11-2.0.so.0
#36 0x00007ffff78d34d9 in gtk_init () from /usr/lib64/libgtk-x11-2.0.so.0
#37 0x000000000041140d in ?? ()
#38 0x00007ffff4b0fbe5 in __libc_start_main () from /lib64/libc.so.6
#39 0x0000000000414eed in ?? ()

glibc-2.18-4.11.1.x86_64
openSUSE 13.1

It looks like it happens the second time entering getKdeHome()

[yuyichao]

Nop, it shouldn't be.

This is what it should look like when gdb recieved a signal

^C
Program received signal SIGINT, Interrupt.
0x00007ffff533391d in poll () from /usr/lib/libc.so.6
(gdb) bt
#0  0x00007ffff533391d in poll () from /usr/lib/libc.so.6
#1  0x00007ffff6f665d8 in g_main_context_poll (priority=0, context=<optimized out>, 
timeout=<optimized out>, fds=<optimized out>, n_fds=<optimized out>)
at gmain.c:4006
#2  g_main_context_iterate (context=<optimized out>, block=<optimized out>, 
dispatch=<optimized out>, self=<optimized out>) at gmain.c:3707
#3  0x00007ffff6f668ff in g_main_loop_run (loop=loop@entry=0xdc7730) at gmain.c:3906
#4  0x00007ffff78d4cd7 in gtk_main () at gtkmain.c:1257
#5  0x00000000004139a6 in ?? ()
#6  0x00007ffff5278b05 in __libc_start_main () from /usr/lib/libc.so.6
#7  0x0000000000413bd9 in ?? ()

The signal handler (if any) should be called after gdb captures it. (And in any case it shouldn't call another function before gdb).

[yuyichao]

P.S. when pasting the output of some command, please quote it as code.

[yuyichao]

info signals should show you how gdb handles each signals.
and handle should allow you to change that.

From the list of signals gdb does not stop or print by default. I guess it's a SIGCHLD. You can check that with handle all print

[yuyichao]

Although I still don't understand why it could hang on wait() ....

[cryptomilk]

Ok, popen() executes kde-config which quits with a SIGCHLD. Then we read what it printed and then pclose hangs waiting for the process to terminate, but it already terminated...

See the manpage for pclose():
The pclose() function waits for the associated process to terminate and returns the exit status of the command as returned by wait4(2).

[cryptomilk]

I think the pclose()/fclose() sets up the signal handler to detect when the application goes away. The process has already finished and calls waitpid() on a process which doesn't exist. So it sits there and waits forever ...

[cryptomilk]

I've tested it outside of qtcurve and it works just fine. I've also set the SA_RESETHAND flag before invoking popen() still doesn't work.

[cryptomilk]

I got it working, it is the SIGCHILD handler ...

[yuyichao]

I still don't think this is the right explaination.
The blocking wait() is in the signal handler of SIGCHLD and this should never block (at least the first one.)
Also, if your first patch have any effect at all, the signal handler is definitely not set up by popen()/pclose().

[cryptomilk]

The runCommand worked just fine using it in a simple programm but doesn't work with some GTK applications. You didn't like that I reset the signal handler so I implemented it using posix_spawn(). What's wrong with posix_spawn now?