On Tue, Jan 18, 2022 at 05:56:47PM -0500, Jason Merrill wrote:
> Debug information was getting confused because input_location was different
> depending on whether we had looked ahead to see if the next tokens look like
> a template argument list.
>
> I tried resetting input_location in cp_lexer_rollback_tokens itself, but
> that caused regressions, so let's just do it here for now.
>
> Tested x86_64-pc-linux-gnu, applying to trunk.
>
> PR c++/104025
>
> gcc/cp/ChangeLog:
>
> * parser.cc (saved_token_sentinel::rollback): Call
> cp_lexer_set_source_position.
> (~saved_token_sentinel): Call rollback.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/warn/pr104025.C: New test.
The testcase fails for me with this change.
I see:
Breakpoint 5, cp_parser_id_expression (parser=0x7fffea26e7b8,
template_keyword_p=false, check_dependency_p=true, template_p=0x7fffffffaf5f,
declarator_p=false, optional_p=false)
at ../../gcc/cp/parser.cc:6257
6257 saved_token_sentinel toks (parser->lexer, STS_ROLLBACK);
(gdb) p expand_location (input_location)
$6 = {file = 0x4162bb0 "pr104025.C", line = 16, column = 12, data = 0x0, sysp =
false}
- input_location is when entering this code conditional on the warning
set to the last committed token, i.e. i in
bar (c.i < m);
Next it commits the < and m tokens (so up to column 16) and then fails
and invokes rollback and cp_lexer_set_source_position. But that sets
input_location from the peeked token, i.e. the < one with column 14.
So, with -w, we get 16:12, without -w we get 16:14.
> --- a/gcc/cp/parser.cc
> +++ b/gcc/cp/parser.cc
> @@ -1308,6 +1308,7 @@ struct saved_token_sentinel
> void rollback ()
> {
> cp_lexer_rollback_tokens (lexer);
> + cp_lexer_set_source_position (lexer);
> mode = STS_DONOTHING;
> }
> ~saved_token_sentinel ()
> @@ -1315,7 +1316,7 @@ struct saved_token_sentinel
> if (mode == STS_COMMIT)
> cp_lexer_commit_tokens (lexer);
> else if (mode == STS_ROLLBACK)
> - cp_lexer_rollback_tokens (lexer);
> + rollback ();
>
> gcc_assert (lexer->saved_tokens.length () == len);
> }
> diff --git a/gcc/testsuite/g++.dg/warn/pr104025.C
> b/gcc/testsuite/g++.dg/warn/pr104025.C
> new file mode 100644
> index 00000000000..9457c8ef52c
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/warn/pr104025.C
> @@ -0,0 +1,20 @@
> +// PR c++/104025
> +// { dg-do compile }
> +// { dg-options "-Wmissing-template-keyword -fcompare-debug" }
> +
> +void bar (int);
> +
> +struct S { int i; };
> +
> +template <class C>
> +struct T
> +{
> + int m;
> + C c;
> + void foo ()
> + {
> + bar (c.i < m);
> + }
> +};
> +
> +template void T<S>::foo ();
>
> base-commit: 7ca21601704c4a637f3cefa7c8814920782354d8
Jakub
