Re: AC_PROG_CC_C99 and AC_OPENMP

[Ralf Wildenhues]

Hello Alfred,

* Alfred M. Szmidt wrote on Sun, May 09, 2010 at 01:39:30PM CEST:
>    It seems a shame that the test for OpenMP does not allow the user
>    to specify a minimum version that the implementation needs to
>    satisfy before it will be used.  OpenMP has been around for quite a
>    while now and there are quite a few versions.
> 
> Testing for a version number is always the wrong approach, since
> another implementation of the library might support the same set of
> features, while having a different version number.  If there are
> specific featutres that are needed, one should test for those.

I think Bob refers to different versions of the OpenMP standard,
as opposed to different versions of some library implementation.
Requiring one of those versions would make sense, similar to how
AC_PROG_CC_C99 requests the 1999 version of the ISO C standard
and not the 1989/90 one.  Of course, the actual test code could,
besides checking the value of _OPENMP, also test for actual features
of the respective standard version, similarly to how AC_PROG_CC_C99
works.  It could do runtime tests when not cross-compiling, and fall
back to link test/_OPENMP value otherwise.

I agree with Bob that this would be a nice addition to Autoconf.

Cheers,
Ralf