Re: fixing AC_OPENMP for Apple clang

On Mon, 2 Mar 2026 at 21:24, Dima Pasechnik <[email protected]> wrote:

> On Mon, Mar 02, 2026 at 05:48:40PM +0100, Florian Weimer wrote:
> > > I think this is an overwhelming evidence in favour of Autoconf
> > > supporting this feature, documented, or not, by the upstream (i.e.
> Apple).
> > > The community knows how to use it, and uses it, there is no need to b=
e
> > > patronising here. By not supporting it Autotools shoot themselves in
> the
> > > foot, forcing users/developers of multi-platform OpenMP-using
> applications
> > > to look elsewhere for a build system supporting this
> > > feature out of the box.
> > > As I said, Meson supports it out of the box. Cmake supports it too.
> >
> > Okay, then it's a bit weird that it's not mentioned at all in the Apple
> > documentation.
>
> I can only speculate that once you bought enough support from them,
> they'd tell you. After all, "-Xpreprocessor -fopenmp" somehow has leaked
> out
> as a working option.
>
> Apparently instead of "-Xpreprocessing" one can use "-Xclang", although
> it appears to be less popular. I don't know the difference between these
> two - perhaps AC_OPENMP (and libtool?) should also test for "-Xclang
> -fopenmp"?
>
> "-Xclang" is briefly mentioned in clang docs:
> https://clang.llvm.org/docs/UsersManual.html
>

Does modern Xcode includes libomp =E2=80=9Cout of the box=E2=80=9D or it ne=
ed to be built
separately from Homebrew/MacPorts/Git? (I have access to Catalina bot not
to more modern version, and on Catalina it doesn=E2=80=99t)