configure seems not able to use openmp on OSX

[hvdwolf]

Max OS X version 10.6 (Snow Leopard).
relates to: release version of enblend 4.0 and mercurial trunk version of enblend.

To be able to use OpenMP on Mac OS X we need at least gcc-4.2 and g++-4.2. These are the default versions on SnowLeopard (and 4.3 on Lion). As I'm on snowLeopard I use the 4.2 versions to compile the openmp versions. I use the 4.0 versions to create the non-openmp versions for backward compatibility with Tiger.

I use "--disable-image-cache --enable-openmp" flags for configure.
However, the configure steps mentions:

checking whether to compile with OpenMP... yes
checking for OpenMP flag of C++ compiler... unknown
no

And the summary at the end mentions:
 enblend-enfuse now configured for i386-apple-darwin9
   Source directory: .
   Installation directory: /Users/Shared/development/hugin_related/ExternalPrograms/3way-repository
   C++ compiler: g++-4.2
<snip>
   use image cache: no
   build GPU acceleration: yes
   use OpenMP: no

If I do nothing, enblend is compiled without openmp support.
However, I do specify the -fopenmp flag in my C/CXX/CPP FLAGS (maybe over the top) and I get perfect openmp versions for ppc, i386 and x86_64.

This configure "failure" was not the case "some year ago". Since then I hardly touched enblend and in the mean time (that past year) I also had a few (minor) updates in both my development environment. I have no clue when this was introduced.

What is causing this?

[Christoph Spiel (cspiel)]

The OpenMP M4 check macro is up to date, so the check proper ought to be ok.

You say: "I do specify the -fopenmp flag in my... I get perfect openmp versions".
So, is the compiler ./configure uses when checking your system a _different_
compiler than the one you can successfully pass the "-fopenmp" flag?

You can check the "config.log" file in your build directory for details.