Re: Minimal GCC version for QEMU

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Mar 11, 2026 at 08:28:01AM +0100, Thomas Huth wrote:
> On 11/03/2026 00.06, nia wrote:
> > On Tue, Mar 10, 2026 at 04:47:30PM +0100, Thomas Huth wrote:
> > > According to that URL from NetBSD that I posted above, they are still using
> > > LLVM 10.0 in NetBSD 10 ... which is also our current minimum version of
> > > Clang, so I assume we're still stuck with Clang v10 for a while?
> > 
> > Since I was CCed in this discussion - can I ask why qemu is targeting
> > compiler versions instead of C standard revisions?
> 
>  Hi!
> 
> QEMU already uses std=gnu11. The problem is that different compiler versions
> emit different warnings, and with older compilers, there are often warnings
> that are false positives (see e.g.
> https://lore.kernel.org/qemu-devel/87h5qn23v5.fsf@suse.de/ that just has
> been posted to the mailing list recently). The QEMU project tries to avoid
> supporting operating systems / build environments that are too old (see
> https://www.qemu.org/docs/master/about/build-platforms.html), we often just
> don't have the capacity in the developer community to handle that, so that's
> why we put compiler checks into place to avoid wrong expectations for the
> users.

Furthermore, the minimum GCC + CLang versions are what we use to
determine what GNU C standard revision we can set as our baseline.
For example see this previous commit:

  commit 8a9d3d564093dbd5a7339085406e840893944d21
  Author: Richard Henderson <richard.henderson@linaro.org>
  Date:   Mon Jun 14 16:31:36 2021 -0700

    configure: Use -std=gnu11
    
    Now that the minimum gcc version is 7.5, we can use C11.
    This will allow lots of cleanups to the code, currently
    hidden behind macros in include/qemu/compiler.h.



With regards,
Daniel
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