Created attachment 89967 [details] [review] reset the error to NULL, so the next call is working That bug exists in 5.16 but doesn't apply to trunk due to some refactoring Way to trigger it: - create a user/.local/share/telepathy where the user has no write rights - try running mission-control - see the warnings and segfault Stacktrace #0 0xb77d1424 in __kernel_vsyscall () #1 0xb7039aff in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 #2 0xb703d083 in __GI_abort () at abort.c:90 #3 0xb7076a95 in __libc_message (do_abort=do_abort@entry=2, fmt=fmt@entry=0xb717a0d0 "*** Error in `%s': %s: 0x%s ***\n") at ../sysdeps/unix/sysv/linux/libc_fatal.c:199 #4 0xb70817c2 in malloc_printerr (action=<optimized out>, str=<optimized out>, ptr=0x863b728) at malloc.c:4923 #5 0xb7082510 in _int_free (av=0xb71bb440 <main_arena>, p=0x863b720, have_lock=0) at malloc.c:3779 #6 0xb72265d0 in g_free (mem=mem@entry=0x863b728) at /build/buildd/glib2.0-2.38.1/./glib/gmem.c:197 #7 0x08085bdd in _commit (self=self@entry=0x85da000, am=am@entry=0x8638a78, account=account@entry=0x0) at mcd-account-manager-default.c:259 #8 0x08085ec0 in _list (self=0x85da000, am=0x8638a78) at mcd-account-manager-default.c:364 #9 0xb7797442 in mcp_account_storage_list (storage=storage@entry=0x85da000, am=am@entry=0x8638a78) at account-storage.c:952 #10 0x0808376e in mcd_storage_load (self=0x8638a78) at mcd-storage.c:740 #11 0x08070937 in _mcd_account_manager_constructed (obj=0x85d8680) at mcd-account-manager.c:1682 The code does g_error_free() an error to reuse it, but without resetting it to NULL, which makes the next call not set a new one and the g_warning hit an invalid read.
You should use g_clear_error() instead. I'm actually tempted to do a big s/g_error_free/g_clear_error/ and ban g_error_free() in our coding style checker, like we already banned some _free() in favor of their corresponding _unref().
(In reply to comment #1) > You should use g_clear_error() instead I agree... > I'm actually tempted to do a big s/g_error_free/g_clear_error/ ... but I think this is going too far - it's often obvious that the error is both non-NULL and no longer used, for instance in this idiom for dealing with errors that there's no way to signal (yes that's a design flaw, but often one that we're stuck with medium-term): static void foo (void) { GError *error = NULL; if (do_a_thing (&error)) { WARNING ("%s", error->message); g_error_free (error); } } or when interacting with dbus-glib: static void do_something_on_dbus (DBusGMethodInvocation *context) { GError *error = NULL; if (do_something (&error)) { dbus_g_method_return (context); } else { dbus_g_method_return_error (context, error); g_error_free (error); } }
Created attachment 90260 [details] [review] new version using g_clear_error ok, updated to use g_clear_error, I've only done that specific change and not tried to replace other uses
Comment on attachment 90260 [details] [review] new version using g_clear_error Review of attachment 90260 [details] [review]: ----------------------------------------------------------------- Looks good to me.
Comment on attachment 90260 [details] [review] new version using g_clear_error Review of attachment 90260 [details] [review]: ----------------------------------------------------------------- Actually, I take that back. This is g_clear_error (error), it needs to be g_clear_error (&error). Did you test this?
Fixed in git for 5.16.1; I added the necessary "&" to make it work.
ups, sorry about that, I test built but didn't test run in the buggy condition ... thanks for catching the error!
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