Accept commas between clauses in OpenMP declare variant

Add support to the Fortran parser for the OpenMP syntax that allows a comma
after the directive name and between clauses of declare variant. The C and C++
parsers already support this syntax so only a new test is added.

gcc/fortran/ChangeLog:

	* openmp.cc (gfc_match_omp_declare_variant): Match comma after directive
	name and between clauses. Emit more useful diagnostics.

gcc/testsuite/ChangeLog:

	* gfortran.dg/gomp/declare-variant-2.f90: Remove error test for a comma
	after the directive name. Add tests for other invalid syntaxes (extra
	comma and invalid clause).
	* c-c++-common/gomp/adjust-args-5.c: New test.
	* gfortran.dg/gomp/adjust-args-11.f90: New test.

1 files changed, 21 insertions, 0 deletions

diff --git a/gcc/testsuite/c-c++-common/gomp/adjust-args-5.c b/gcc/testsuite/c-c++-common/gomp/adjust-args-5.c
new file mode 100644
index 0000000..8aff73c
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/gomp/adjust-args-5.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+
+/* Check that the OpenMP 5.1 syntax with commas after the directive name and
+   between clauses is supported. */
+
+int f (int a, void *b, float c[2]);
+
+#pragma omp declare variant (f), match (construct={dispatch}), adjust_args (nothing: a), adjust_args (need_device_ptr: b, c)
+int f0 (int a, void *b, float c[2]);
+
+int test () {
+  int a;
+  void *b;
+  float c[2];
+  struct {int a;} s;
+
+  #pragma omp dispatch, novariants(0), nocontext(1)
+  s.a = f0 (a, b, c);
+
+  return s.a;
+}