[Bug c/95130] GCC ignoring attribute(format(gnu_printf)) on printf in mingw

["tomas.kalibera at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95130

--- Comment #11 from Tomas Kalibera <tomas.kalibera at gmail dot com> ---
(In reply to LIU Hao from comment #10)
> (In reply to Tomas Kalibera from comment #7)
> > I sent an updated version for the trunk, 12, 11 and 10 to the gcc-patches
> > mailing list in May:
> > 
> > https://gcc.gnu.org/pipermail/gcc-patches/2022-May/594960.html
> > 
> > The patches still apply to current 10,11,12 and trunk. Please see the email
> > linked above for more information.
> 
> 
> Thanks for the patch. Updated locally. I will test it against trunk as soon
> as I get a little time.

Thanks. Re Jeff's comment from the mailing list:

> I guess we're going to depend on the builtin-format always appearing 
> first in the chain?  While it's probably true in practice, I doubt we 
> really want to depend on that.
>
> Is there any sensible way to distinguish between the builtin format and 
> one that comes from the source?

I didn't find any elegant way to find out whether a format attribute is a
built-in attribute in check_function_format(). So unless I overlooked something
(which is very much possible), it would make the patch more intrusive.

handle_format_attribute() has that information in flags (ATTR_FLAG_BUILT_IN).
Maybe handle_format_attribute() could add the flags (or only a boolean whether
it is a builtin attribute) to the attribute tree, so that
check_function_format() can access it, e.g. similarly to how no_sanitize does
it. Would this be better? And if so, is there a recommended place in the format
attribute tree where it should be added to?