[gcc r12-3831] openmp: Diagnose omp::directive attribute without balanced token argument [PR102413]

[Jakub Jelinek <jakub@gcc.gnu.org>]

https://gcc.gnu.org/g:0d39eb28fd2ab00306bd7c0a87b6c0ed615b5d12

commit r12-3831-g0d39eb28fd2ab00306bd7c0a87b6c0ed615b5d12
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Sep 23 10:07:49 2021 +0200

    openmp: Diagnose omp::directive attribute without balanced token argument [PR102413]
    
    If omp::directive attribute argument starting with the opening ( is not a balanced
    token sequence, then cp_parser_skip_balanced_tokens (parser, 1) returns 1,
    but the code was subtracting 2 from it and iterating until it was 0, so for the
    non-balanced case it iterated from (size_t) -1 down to 0.
    
    The following patch just diagnoses that as an error.
    
    2021-09-23  Jakub Jelinek  <jakub@redhat.com>
    
            PR c++/102413
            * parser.c (cp_parser_omp_directive_args): Diagnose if omp::directive
            is not followed by a balanced token sequence starting with open paren.
    
            * g++.dg/gomp/attrs-14.C: New test.

Diff:
---
 gcc/cp/parser.c                      | 11 ++++++++++-
 gcc/testsuite/g++.dg/gomp/attrs-14.C |  4 ++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 26d925c15c5..052fa25ebda 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -28628,7 +28628,16 @@ cp_parser_omp_directive_args (cp_parser *parser, tree attribute)
       TREE_VALUE (attribute) = NULL_TREE;
       return;
     }
-  for (size_t n = cp_parser_skip_balanced_tokens (parser, 1) - 2; n; --n)
+  size_t n = cp_parser_skip_balanced_tokens (parser, 1);
+  if (n == 1)
+    {
+      cp_lexer_consume_token (parser->lexer);
+      error_at (first->location, "expected attribute argument as balanced "
+				 "token sequence");
+      TREE_VALUE (attribute) = NULL_TREE;
+      return;
+    }
+  for (n = n - 2; n; --n)
     cp_lexer_consume_token (parser->lexer);
   cp_token *last = cp_lexer_peek_token (parser->lexer);
   cp_lexer_consume_token (parser->lexer);
diff --git a/gcc/testsuite/g++.dg/gomp/attrs-14.C b/gcc/testsuite/g++.dg/gomp/attrs-14.C
new file mode 100644
index 00000000000..959f7764cf1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/gomp/attrs-14.C
@@ -0,0 +1,4 @@
+// PR c++/102413
+// { dg-do compile { target c++11 } }
+
+[[omp::directive(error]];	// { dg-error "expected|declare" }