On Tue, 24 Nov 2020 at 12:52, <marcandre.lureau@redhat.com> wrote:
>
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>
> Hi,
>
> Since commit efc6c07 ("configure: Add a test for the minimum compiler version=
> "),
> QEMU explicitely depends on GCC >= 4.8.
You need to be a bit cautious about removing QEMU_GNUC_PREREQ()
checks, because clang advertises itself as GCC 4.2 via the
__GNUC__ and __GNUC_MINOR__ macros that QEMU_GNUC_PREREQ()
tests, and so unless the code has explicitly handled clang
via a different ifdef or feature test clang will be using
the fallback codepath in cases like this. So you also need
to find out whether all our supported versions of clang
are OK with the gcc-4.4-and-up version of the code before
removing any particular ifdef.
Compare this previous (not-applied) patchset from Philippe:
https://patchew.org/QEMU/20200928125859.734287-1-philmd@redhat.com/
which dealt with two of these ifdefs, one of which is
"clearly OK" and the other of which is "needs more analysis".
The path forward I think is along those lines -- we need
one patch per ifdef we're trying to remove, and the commit
message can then include the information about why in
this case it is OK for clang too (or switch the ifdef
to check for something else, eg one of clang's feature-specific
test macros).
Thanks for pointing out the series, I missed it. Ok, I'll try to do some more research.