Re: fixing AC_OPENMP for Apple clang

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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. Appl=
e).
> > The community knows how to use it, and uses it, there is no need to be
> > patronising here. By not supporting it Autotools shoot themselves in the
> > foot, forcing users/developers of multi-platform OpenMP-using applicati=
ons
> > 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.
>=20
> 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 -fopen=
mp"?

"-Xclang" is briefly mentioned in clang docs: https://clang.llvm.org/docs/U=
sersManual.html


Best,
Dima


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