c++: Fix endless errors on invalid requirement seq [PR97742]

As the testcase shows, if we reach CPP_EOF during parsing of requirement
sequence, we end up with endless loop where we always report invalid
requirement expression, don't consume any token (as we are at eof) and
repeat.

This patch stops the loop when we reach CPP_EOF.

2021-02-12  Jakub Jelinek  <jakub@redhat.com>

	PR c++/97742
	* parser.c (cp_parser_requirement_seq): Stop iterating after reaching
	CPP_EOF.

	* g++.dg/cpp2a/concepts-requires24.C: New test.

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index d68dcb7..7077579 100644 (file)
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -28807,7 +28807,9 @@ cp_parser_requirement_seq (cp_parser *parser)
       tree req = cp_parser_requirement (parser);
       if (req != error_mark_node)
        result = tree_cons (NULL_TREE, req, result);
-    } while (cp_lexer_next_token_is_not (parser->lexer, CPP_CLOSE_BRACE));
+    }
+  while (cp_lexer_next_token_is_not (parser->lexer, CPP_CLOSE_BRACE)
+        && cp_lexer_next_token_is_not (parser->lexer, CPP_EOF));
 
   /* If there are no valid requirements, this is not a valid expression. */
   if (!result)

diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires24.C b/gcc/testsuite/g++.dg/cpp2a/concepts-requires24.C
new file mode 100644 (file)
index 0000000..597528b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires24.C
@@ -0,0 +1,4 @@
+// PR c++/97742
+// { dg-do compile { target c++20 } }
+
+template <int = requires { true        // { dg-error "expected" }