Daniel P. Berrangé <[email protected]> writes: > On Tue, Nov 25, 2025 at 08:40:07AM +0100, Markus Armbruster wrote: >> g_autoptr(T) is quite useful when the object's extent matches the >> function's. >> >> This isn't the case for an Error object the function propagates to its >> caller. It is the case for an Error object the function reports or >> handles itself. However, the functions to report Error also free it. >> >> Thus, g_autoptr(Error) is rarely applicable. We have just three >> instances out of >1100 local Error variables, all in migration code. >> >> Two want to move the error to the MigrationState for later handling / >> reporting. Since migrate_set_error() doesn't move, but stores a copy, >> the original needs to be freed, and g_autoptr() is correct there. We >> have 17 more that instead manually free with error_free() or >> error_report_err() right after migrate_set_error(). >> >> We recently discussed storing a copy vs. move the original: >> >> From: Peter Xu <[email protected]> >> Subject: Re: [PATCH 0/3] migration: Error fixes and improvements >> Date: Mon, 17 Nov 2025 11:03:37 -0500 >> Message-ID: <[email protected]> >> >> The two g_autoptr() gave me pause when I investigated this topic, simply >> because they deviate from the common pattern migrate_set_error(s, err) >> followed by error_free() or error_report_err(). >> >> The third one became wrong when I cleaned up the reporting (missed in >> the cleanup patch, fixed in the patch I'm replying to). I suspect my >> mistake escaped review for the same reason I made it: g_autoptr(Error) >> is unusual and not visible in the patch hunk. >> >> Would you like me to replace the two correct uses of g_autoptr(Error) by >> more common usage? > > I had previously proposed g_autoptr(Error) a year or two back and you > rejected it then, so I'm surprised to see that it got into the code, > because it requires explicit opt-in via a G_DEFINE_AUTOPTR_CLEANUP_FUNC. > > Unfortunately it appears exactly that was added earlier this year in > > commit 18eb55546a54e443d94a4c49286348176ad4b00a > Author: Maciej S. Szmigiero <[email protected]> > Date: Tue Mar 4 23:03:35 2025 +0100 > > error: define g_autoptr() cleanup function for the Error type > > Automatic memory management helps avoid memory safety issues. > > Reviewed-by: Peter Xu <[email protected]> > Signed-off-by: Maciej S. Szmigiero <[email protected]> > Link: > https://lore.kernel.org/qemu-devel/a5843c5fa64d7e5239a4316092ec0ef0d10c2320.1741124640.git.maciej.szmigi...@oracle.com > Signed-off-by: Cédric Le Goater <[email protected]>
I missed it. Not he submitter's fault; it was cc'ed to me. > When removing this usage, ensure that commit is reverted too, which > will prevent anyone unwittingly re-introducing g_autoptr(Error) > usage Thanks for the pointer!
