xdg-autostart: never reuse GKeyFile object

[mtasaka]

As written on:
https://developer.gnome.org/glib/stable/glib-Key-value-file-parser.html#g-key-file-load-from-file
an empty GKeyFile object must be passed to g_key_file_load_from_file .

==============================================================
With Fedora 34 (in development state, will be released on 2021/Apr), using glib2-2.67.6, I've noticed that LXDE session no longer launches programs specified by "autostart" desktop file, then I've identified that lxsession-xdg-autostart is segfaulting:

$ gdb ./lxsession-xdg-autostart 
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Reading symbols from ./lxsession-xdg-autostart...
(gdb) r
Starting program: /home/tasaka1/rpmbuild/fedora-specific/LXDE/lxsession/rawhide/lxsession-0.5.5/lxsession/xdg-autostart/lxsession-xdg-autostart 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
g_key_file_locale_is_interesting (locale=0x555555569940 "ja_JP", key_file=0x555555568800) at ../glib/gkeyfile.c:1241
1241	  for (i = 0; key_file->locales[i] != NULL; i++)
Missing separate debuginfos, use: dnf debuginfo-install libffi-3.1-28.fc34.x86_64 pcre-8.44-3.fc34.1.x86_64
(gdb) bt
#0  g_key_file_locale_is_interesting (locale=0x555555569940 "ja_JP", key_file=0x555555568800) at ../glib/gkeyfile.c:1241
#1  g_key_file_parse_key_value_pair (error=0x7fffffffcc40, length=<optimized out>, line=<optimized out>, key_file=0x555555568800)
    at ../glib/gkeyfile.c:1427
#2  g_key_file_parse_line (error=0x7fffffffcc38, length=<optimized out>, line=<optimized out>, key_file=0x555555568800)
    at ../glib/gkeyfile.c:1273
#3  g_key_file_flush_parse_buffer (key_file=key_file@entry=0x555555568800, error=error@entry=0x7fffffffcca0) at ../glib/gkeyfile.c:1542
#4  0x00007ffff7ebdd3c in g_key_file_parse_data
    (key_file=0x555555568800, data=0x7fffffffcda0 "\n[Desktop Entry]\nType=Application\nName=GNOME Login Sound\nExec=/usr/bin/canberra-gtk-play --id=\"desktop-login\" --description=\"GNOME Login\"\nOnlyShowIn=GNOME;\nAutostartCondition=GNOME /desktop/gnome/soun"..., length=384, error=0x7fffffffcd08) at ../glib/gkeyfile.c:1496
#5  0x00007ffff7ebdfb9 in g_key_file_load_from_fd
    (key_file=key_file@entry=0x555555568800, fd=fd@entry=3, flags=flags@entry=G_KEY_FILE_NONE, error=error@entry=0x7fffffffddf0)
    at ../glib/gkeyfile.c:857
#6  0x00007ffff7ebe0b4 in g_key_file_load_from_file
    (key_file=key_file@entry=0x555555568800, file=<optimized out>, flags=flags@entry=G_KEY_FILE_NONE, error=error@entry=0x0)
    at ../glib/gkeyfile.c:924
#7  0x00005555555567d1 in launch_autostart_file (desktop_id=<optimized out>, desktop_file=<optimized out>, kf=0x555555568800)
    at xdg-autostart/xdg-autostart.c:180
#8  0x00007ffff7ea94f8 in g_hash_table_foreach
    (hash_table=0x55555555b1e0 = {...}, func=0x5555555567a0 <launch_autostart_file>, user_data=0x555555568800) at ../glib/ghash.c:2065
#9  0x0000555555556af6 in xdg_autostart (de_name_arg=<optimized out>) at xdg-autostart/xdg-autostart.c:317
#10 0x0000555555556677 in lxsession_main_main (args_length1=<optimized out>, args=<optimized out>) at xdg-autostart/main.c:129
#11 main (argc=<optimized out>, argv=<optimized out>) at xdg-autostart/main.c:145
(gdb) p *key_file
$1 = {groups = 0x555555566b60 = {0x555555566b80, 0x555555566e20}, group_hash = 0x55555555b8c0 = {[0x555555569c20 "Desktop Entry"] = 0x555555566b80}, start_group = 0x555555566b80, 
  current_group = 0x555555566b80, parse_buffer = 0x555555566ba0, list_separator = 59 ';', flags = G_KEY_FILE_NONE, checked_locales = 1, locales = 0x0, ref_count = 1}

The key here is that locales is NULL, however checked_locales is 1, not 0. https://gitlab.gnome.org/GNOME/glib/-/blob/b3384e5797de3226224927190e9f7cd0973ac168/glib/gkeyfile.c#L1235
As written above, GKeyFile object must not be reused for g_key_file_load_from_file .

[mtasaka]

Well, https://gitlab.gnome.org/GNOME/glib/-/issues/2361 says glib side fixed this issue on 2.68.1. I will check this later.

[ib]

Could you check it?

[ib]

Seems to be fixed now.