[Bug c++/66290] wrong location for -Wunused-macros

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66290

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Lewis Hyatt <lhyatt@gcc.gnu.org>:

https://gcc.gnu.org/g:b04c399e258e686dddad879bf7e27d9e28fd6fde

commit r13-1903-gb04c399e258e686dddad879bf7e27d9e28fd6fde
Author: Lewis Hyatt <lhyatt@gmail.com>
Date:   Tue Jul 12 09:47:47 2022 -0400

    c++: Fix location for -Wunused-macros [PR66290]

    In C++, since all tokens are lexed from libcpp up front, diagnostics
generated
    by libcpp after lexing has completed do not get a valid location from
libcpp
    (rather, libcpp thinks they all pertain to the end of the file.) This has
long
    been addressed using the global variable "done_lexing", which the C++
frontend
    sets at the appropriate time; when done_lexing is true, then
c_cpp_diagnostic(),
    which outputs libcpp's diagnostics, uses input_location instead of the
wrong
    libcpp location. The C++ frontend arranges that input_location will point
to the
    token it is currently processing, so this generally works fine. However,
there
    is one exception currently, which is -Wunused-macros. This gets generated
at the
    end of processing in cpp_finish (), since we need to wait until then to
    determine whether a macro was eventually used or not. But the locations it
    passes to c_cpp_diagnostic () were remembered from the original lexing and
hence
    they should not be overridden with input_location, which is now the one
    incorrectly pointing to the end of the file.

    Fixed by setting done_lexing=false again just prior to calling cpp_finish
(). I
    also renamed the variable from done_lexing to "override_libcpp_locations",
since
    it's now not strictly about lexing anymore.

    There is no new testcase with this patch, since we already had an xfailed
    testcase which is now fixed.

    gcc/c-family/ChangeLog:

            PR c++/66290
            * c-common.h: Rename global done_lexing to
            override_libcpp_locations.
            * c-common.cc (c_cpp_diagnostic): Likewise.
            * c-opts.cc (c_common_finish): Set override_libcpp_locations
            (formerly done_lexing) immediately prior to calling cpp_finish ().

    gcc/cp/ChangeLog:

            PR c++/66290
            * parser.cc (cp_lexer_new_main): Rename global done_lexing to
            override_libcpp_locations.

    gcc/testsuite/ChangeLog:

            PR c++/66290
            * c-c++-common/pragma-diag-15.c: Remove xfail for C++.