On Thu, Feb 11, 2021 at 05:30:24PM +0100, Jakub Jelinek via Gcc-patches wrote:
> Hi!
>
> 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.
>
> Ok for trunk if it passes bootstrap/regtest?
LGTM.
> 2021-02-11 Jakub Jelinek <ja...@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.
>
> --- gcc/cp/parser.c.jj 2021-02-03 17:14:01.000000000 +0100
> +++ gcc/cp/parser.c 2021-02-11 14:44:05.877357556 +0100
> @@ -28816,7 +28816,9 @@ cp_parser_requirement_seq (cp_parser *pa
> 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)
> --- gcc/testsuite/g++.dg/cpp2a/concepts-requires24.C.jj 2021-02-11
> 14:40:28.548815748 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/concepts-requires24.C 2021-02-11
> 14:39:40.209362526 +0100
> @@ -0,0 +1,4 @@
> +// PR c++/97742
> +// { dg-do compile { target c++20 } }
> +
> +template <int = requires { true // { dg-error "expected" }
>
> Jakub
>
Marek
