Re: [PATCH v2] build: remove obsolete compiler checks

[Bruce Richardson <bruce.richardson@intel.com>]

On Tue, Aug 19, 2025 at 10:10:21AM +0200, David Marchand wrote:
> Hello Bruce,
> 
> On Fri, Jul 25, 2025 at 6:07 PM Bruce Richardson
> <bruce.richardson@intel.com> wrote:
> > diff --git a/drivers/net/virtio/meson.build b/drivers/net/virtio/meson.build
> > index d3caa3a3b4..a9ff87e863 100644
> > --- a/drivers/net/virtio/meson.build
> > +++ b/drivers/net/virtio/meson.build
> > @@ -31,7 +31,7 @@ if arch_subdir == 'x86'
> >          sources_avx512 += files('virtio_rxtx_packed.c')
> >          if (toolchain == 'gcc' and cc.version().version_compare('>=8.3.0'))
> >              cflags += '-DVIRTIO_GCC_UNROLL_PRAGMA'
> > -        elif (toolchain == 'clang' and cc.version().version_compare('>=3.7.0'))
> > +        elif (toolchain == 'clang')
> >              cflags += '-DVIRTIO_CLANG_UNROLL_PRAGMA'
> >          endif
> >      endif
> 
> [snip]
> 
> > diff --git a/lib/vhost/meson.build b/lib/vhost/meson.build
> > index 9c6325aa0e..a74d0cff7c 100644
> > --- a/lib/vhost/meson.build
> > +++ b/lib/vhost/meson.build
> > @@ -8,9 +8,9 @@ endif
> >  if has_libnuma
> >      dpdk_conf.set10('RTE_LIBRTE_VHOST_NUMA', true)
> >  endif
> > -if (toolchain == 'gcc' and cc.version().version_compare('>=8.3.0'))
> > +if (toolchain == 'gcc')
> >      cflags += '-DVHOST_GCC_UNROLL_PRAGMA'
> > -elif (toolchain == 'clang' and cc.version().version_compare('>=3.7.0'))
> > +elif (toolchain == 'clang')
> >      cflags += '-DVHOST_CLANG_UNROLL_PRAGMA'
> >  endif
> >  dpdk_conf.set('RTE_LIBRTE_VHOST_POSTCOPY', cc.has_header('linux/userfaultfd.h'))
> 
> Sorry, I did not notice in the v1, but lib/vhost and
> drivers/net/virtio have the same construct, yet only lib/vhost gets
> updated on the gcc version check in this patch.
> Is this intentional?
> 
> Since GCC 8.0+ is recommended, I would keep the version check in both
> vhost and net/virtio.
> 

Checking quickly with Godbolt, the pragma seems to be recognised by GCC 8.1
in the same way as with GCC 8.3. Therefore removing the version check looks
the correct option to me.

However, a better cleanup is to remove these defines from the meson.build
file completely, and instead just check for GCC and clang directly in the
header file.

/Bruce