https://gcc.gnu.org/g:065a6ab3747fe9116643ac6754582bc195847bfc
commit r16-7437-g065a6ab3747fe9116643ac6754582bc195847bfc Author: Marek Polacek <[email protected]> Date: Mon Feb 9 13:54:39 2026 -0500 c++: fix for saved_token_sentinel In cp_parser_splice_spec_is_nns_p I didn't use saved_token_sentinel: its rollback uses cp_lexer_previous_token so if we are the first token in the file, there are no previous tokens so we crash. It would be simple to just use the _safe variant of cp_lexer_previous_token and be done with this. But that's not how this worked out: I saw a new -fcompare-debug FAIL with pr104025.C. The problem is that at the end of cp_parser_id_expression we have a saved_token_sentinel guarded by warn_missing_template_keyword and in that spot lexer->buffer is NULL (so cp_lexer_set_source_position_from_token would be skipped). pr104025.C is compiled twice, the second time with "-w -fcompare-debug-second". So the first time we don't _set_source_position back to where we were after the _skip_entire_template_parameter_list (lexer->buffer is NULL) and the second time we don't get to the saved_token_sentinel at all. That left us with different columns in the location: "pr104025.C":16:16 vs "pr104025.C":16:12 thus the -fcompare-debug FAIL. I assume we don't want -fcompare-debug to ignore the column location. So we could just save input_location in saved_token_sentinel instead of trying to recover it. And then cp_parser_splice_spec_is_nns_p can be simplified. gcc/cp/ChangeLog: * parser.cc (struct saved_token_sentinel): Save input_location. (saved_token_sentinel::rollback): Restore input_location. (cp_parser_splice_spec_is_nns_p): Use saved_token_sentinel. Refactor. Reviewed-by: Jason Merrill <[email protected]> Diff: --- gcc/cp/parser.cc | 21 ++++++--------------- 1 file changed, 6 insertions(+), 15 deletions(-) diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc index 986605e0cdc1..8c46b260fffd 100644 --- a/gcc/cp/parser.cc +++ b/gcc/cp/parser.cc @@ -1635,10 +1635,11 @@ struct saved_token_sentinel { cp_lexer *lexer; unsigned len; + location_t loc; saved_token_sentinel_mode mode; saved_token_sentinel (cp_lexer *_lexer, saved_token_sentinel_mode _mode = STS_COMMIT) - : lexer (_lexer), mode (_mode) + : lexer (_lexer), loc (input_location), mode (_mode) { len = lexer->saved_tokens.length (); cp_lexer_save_tokens (lexer); @@ -1646,8 +1647,7 @@ struct saved_token_sentinel void rollback () { cp_lexer_rollback_tokens (lexer); - cp_lexer_set_source_position_from_token - (cp_lexer_previous_token (lexer)); + input_location = loc; mode = STS_DONOTHING; } ~saved_token_sentinel () @@ -6523,18 +6523,9 @@ cp_parser_skip_entire_splice_expr (cp_parser *parser) static bool cp_parser_splice_spec_is_nns_p (cp_parser *parser) { - /* ??? It'd be nice to use saved_token_sentinel, but its rollback - uses cp_lexer_previous_token, but we may be the first token in the - file so there are no previous tokens. Sigh. */ - cp_lexer_save_tokens (parser->lexer); - - const bool ok = (cp_parser_skip_entire_splice_expr (parser) - && cp_lexer_next_token_is (parser->lexer, CPP_SCOPE)); - - /* Roll back the tokens we skipped. */ - cp_lexer_rollback_tokens (parser->lexer); - - return ok; + saved_token_sentinel toks (parser->lexer, STS_ROLLBACK); + return (cp_parser_skip_entire_splice_expr (parser) + && cp_lexer_next_token_is (parser->lexer, CPP_SCOPE)); } /* Return true if the N-th token is '[:' and its closing ':]' is NOT
