gcc/testsuite/gcc.dg/gomp/macro-3.c

/* PR preprocessor/27746 */
/* { dg-do compile } */
/* { dg-options "-fopenmp -fdump-tree-omplower" } */

#define omp		FOO
#define p		parallel
#define omp_parallel	_Pragma ("omp parallel")
#define omp_p		_Pragma ("omp p")

void bar (void);

void
foo (void)
{
  #pragma omp parallel
    bar ();
  #pragma omp p
    bar ();
  omp_parallel
    bar ();
  omp_p
    bar ();
}

/* { dg-final { scan-tree-dump-times "#pragma omp parallel" 4 "omplower" } } */