openmp: Fix ICE on requires clause with atomic_default_mem_order (

When working on error directive, I've noticed the C FE ICEs on
  #pragma omp requires atomic_default_mem_order (
where it tries to peek 2nd token after the CPP_PRAGMA_EOL (or CPP_EOF)
in there in order to improve error-recovery on say
atomic_default_mem_order (acquire)
or
atomic_default_mem_order (seqcst)
etc.  The C++ FE didn't ICE, but it is better to follow the same thing there.

2021-08-19  Jakub Jelinek  <jakub@redhat.com>

gcc/c/
	* c-parser.c (c_parser_omp_requires): Don't call
	c_parser_peek_2nd_token and optionally consume token if current
	token is CPP_EOF, CPP_PRAGMA_EOL or CPP_CLOSE_PAREN.
gcc/cp/
	* parser.c (cp_parser_omp_requires): Don't call cp_lexer_nth_token_is
	and optionally consume token if current token is CPP_EOF,
	CPP_PRAGMA_EOL or CPP_CLOSE_PAREN.
gcc/testsuite/
	* c-c++-common/gomp/requires-3.c: Add testcase for
	atomic_default_mem_order ( at the end of line without corresponding ).

1 files changed, 12 insertions, 3 deletions

diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index d5f51b1..407f279 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -21710,9 +21710,18 @@ c_parser_omp_requires (c_parser *parser)
 		      error_at (c_parser_peek_token (parser)->location,
 				"expected %<seq_cst%>, %<relaxed%> or "
 				"%<acq_rel%>");
-		      if (c_parser_peek_2nd_token (parser)->type
-			  == CPP_CLOSE_PAREN)
-			c_parser_consume_token (parser);
+		      switch (c_parser_peek_token (parser)->type)
+			{
+			case CPP_EOF:
+			case CPP_PRAGMA_EOL:
+			case CPP_CLOSE_PAREN:
+			  break;
+			default:
+			  if (c_parser_peek_2nd_token (parser)->type
+			      == CPP_CLOSE_PAREN)
+			    c_parser_consume_token (parser);
+			  break;
+			}
 		    }
 		  else
 		    c_parser_consume_token (parser);