To activate the OpenMP extensions for C/C++ and Fortran, the compile-time
flag -fopenmp must be specified. For C and C++, this enables
the handling of the OpenMP directives using #pragma omp and the
[[omp::directive(...)]], [[omp::sequence(...)]] and
[[omp::decl(...)]] attributes. For Fortran, it enables for
free source form the !$omp sentinel for directives and the
!$ conditional compilation sentinel and for fixed source form the
c$omp, *$omp and !$omp sentinels for directives and
the c$, *$ and !$ conditional compilation sentinels.
The flag also arranges for automatic linking of the OpenMP runtime library
(OpenMP Runtime Library Routines).
The -fopenmp-simd flag can be used to enable a subset of OpenMP directives that do not require the linking of either the OpenMP runtime library or the POSIX threads library.
A complete description of all OpenMP directives may be found in the OpenMP Application Program Interface manuals. See also OpenMP Implementation Status.