Re: [PULL 21/26] configure, meson: move more compiler checks to Meson

[Peter Maydell]

On Mon, 15 Nov 2021 at 16:36, Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Thu, 14 Oct 2021 at 17:49, Paolo Bonzini <pbonzini@redhat.com> wrote:
> >
> > Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > Message-Id: <20211007130829.632254-15-pbonzini@redhat.com>
> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> > ---
> >  configure        | 91 ------------------------------------------------
> >  meson.build      | 44 +++++++++++++++++++++++
> >  util/meson.build |  4 ++-
> >  3 files changed, 47 insertions(+), 92 deletions(-)
>
>
> > diff --git a/meson.build b/meson.build
> > index 6bf43e6d30..6b7487b725 100644
> > --- a/meson.build
> > +++ b/meson.build
> > @@ -1550,6 +1550,8 @@ config_host_data.set('CONFIG_INOTIFY',
> >                       cc.has_header_symbol('sys/inotify.h', 'inotify_init'))
> >  config_host_data.set('CONFIG_INOTIFY1',
> >                       cc.has_header_symbol('sys/inotify.h', 
> > 'inotify_init1'))
> > +config_host_data.set('CONFIG_IOVEC',
> > +                     cc.has_header_symbol('sys/uio.h', 'struct iovec'))
> >  config_host_data.set('CONFIG_MACHINE_BSWAP_H',
> >                       cc.has_header_symbol('machine/bswap.h', 'bswap32',
> >                                            prefix: '''#include 
> > <sys/endian.h>
>
> Hi -- I've just noticed that this change breaks compilation for me,
> because this test incorrectly fails to set CONFIG_IOVEC on a system
> where the header defines 'struct iovec'. This seems to be because
> "struct iovec" isn't a valid thing to test with has_header_symbol,
> because it provokes a compiler error from clang.

https://github.com/mesonbuild/meson/issues/1975 says that for gcc
it's actually going to be wrong the other way (always setting CONFIG_IOVEC
whether the system header has the struct or not), because "struct wombat;"
is syntactically OK as a *declaration*, not a use.

Maybe we can work around this by testing for the presence of something else,
eg IOV_MAX or the readv or writev functions ?

-- PMM