Testing for OpenMP?

[Bob Friesenhahn]

What is the recommended way to check to see if OpenMP is supported 
from within a configure script?  I am already using AC_OPENMP([C]) but 
it does not actually check for OpenMP.  All it verifies is that a 
compiler option is selected which does not result in an error, or 
create an output file.  This makes AC_OPENMP not terribly useful other 
than possibly enabling the functionality.

If there is a way to check to see that _OPENMP is defined after CFLAGS 
has been updated, then that would be a positive check.  How can I 
easily do that?

Bob
======================================
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/