[Bug preprocessor/53920] New: "gcc -E" does not honor #pragma GCC diagnostic ignored "-Wunused-macro"

[Bug preprocessor/53920] New: "gcc -E" does not honor #pragma GCC diagnostic ignored "-Wunused-macro"

[naesten at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53920

             Bug #: 53920
           Summary: "gcc -E" does not honor #pragma GCC diagnostic ignored
                    "-Wunused-macro"
    Classification: Unclassified
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: naesten@gmail.com


iMac:gcc-bugs user$ cat cpp-pragma-GCC-diagnostic.c

#pragma GCC diagnostic ignored "-Wunused-macros"
#define FOO

iMac:gcc-bugs user$ gcc-fsf-4.7 -Wunused-macros cpp-pragma-GCC-diagnostic.c -E
# 1 "cpp-pragma-GCC-diagnostic.c"
# 1 "<command-line>"
# 1 "cpp-pragma-GCC-diagnostic.c"

#pragma GCC diagnostic ignored "-Wunused-macros"
cpp-pragma-GCC-diagnostic.c:3:0: warning: macro "FOO" is not used
[-Wunused-macros]
iMac:gcc-bugs user$ gcc-fsf-4.7 --version
gcc-fsf-4.7 (GCC) 4.7.1
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[Bug preprocessor/53920] "gcc -E" does not honor #pragma GCC diagnostic ignored "-Wunused-macro"

[naesten at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53920

--- Comment #1 from Samuel Bronson <naesten at gmail dot com> 2012-07-10 19:07:26 UTC ---
Oh, I suppose I should mention that I ran into this because I was using ccache
to compile Emacs with --enable-gcc-warnings, and by default ccache runs the
preprocessor and the compiler in separate passes (so that it can skip the
compilation proper if it has cached output for a given preprocessor output),
and then pastes together the diagnostic output from the two passes.

(Thankfully, setting the environment variable CCACHE_CPP2 causes ccache to
throw out the preprocessor output after hashing, which is a quite effective
workaround for this sort of thing, though preprocessing the source twice does
make things a bit slower on cache misses.)

[Bug preprocessor/53920] "gcc -E" does not honor #pragma GCC diagnostic ignored "-Wunused-macro"

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53920

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-11-16
                 CC|                            |manu at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #2 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
The C FE normally preprocesses and parses concurrently. But -E (only
preprocessing) is handled by a different function in
c-ppoutput.c(scan_translation_unit), which does not handle pragma diagnostics.
So someone would need to add that handling there. Probably not difficult. I
think one just needs to call c_invoke_pragma handler when a pragma diagnostic
is detected, but someone has to try and flush out the details. If you need help
just ask.
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Subject: [Bug c++/48914] #pragma GCC diagnostic ignored "-Wc++0x-compat" doesn't work
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48914

--- Comment #9 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
If this warning is given by the preprocessor during lexing, then this is a dup
of bug 53431.
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idX771

--- Comment #5 from Paul Thomas <pault at gcc dot gnu.org> ---
Author: pault
Date: Sat Nov 16 21:44:56 2013
New Revision: 204907

URL: http://gcc.gnu.org/viewcvs?rev 4907&root=gcc&view=rev
Log:
2013-11-16  Paul Thomas  <pault@gcc.gnu.org>

    PR fortran/58771
    * trans-io.c (transfer_expr): If the backend_decl for a derived
    type is missing, build it with gfc_typenode_for_spec.

2013-11-16  Paul Thomas  <pault@gcc.gnu.org>

    PR fortran/58771
    * gfortran.dg/derived_external_function_1.f90 : New test

Added:

branches/gcc-4_8-branch/gcc/testsuite/gfortran.dg/derived_external_function_1.f90
Modified:
    branches/gcc-4_8-branch/gcc/fortran/ChangeLog
    branches/gcc-4_8-branch/gcc/fortran/trans-io.c
    branches/gcc-4_8-branch/gcc/testsuite/ChangeLog

[Bug preprocessor/53920] "gcc -E" does not honor #pragma GCC diagnostic ignored "-Wunused-macro"

[markus at oberhumer dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53920

Markus F.X.J. Oberhumer <markus at oberhumer dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |markus at oberhumer dot com

--- Comment #3 from Markus F.X.J. Oberhumer <markus at oberhumer dot com> ---
Still a problem in 2021 with gcc-11.1.0

[Bug preprocessor/53920] "gcc -E" does not honor #pragma GCC diagnostic ignored "-Wunused-macro"

[lhyatt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53920

--- Comment #4 from Lewis Hyatt <lhyatt at gcc dot gnu.org> ---
*** Bug 64698 has been marked as a duplicate of this bug. ***

[Bug preprocessor/53920] "gcc -E" does not honor #pragma GCC diagnostic ignored "-Wunused-macro"

[lhyatt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53920

Lewis Hyatt <lhyatt at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |lhyatt at gcc dot gnu.org

--- Comment #5 from Lewis Hyatt <lhyatt at gcc dot gnu.org> ---
I have a patch awaiting review to fix PR53431 which would fix this one too.
https://gcc.gnu.org/pipermail/gcc-patches/2022-May/595556.html

[Bug preprocessor/53920] "gcc -E" does not honor #pragma GCC diagnostic ignored "-Wunused-macro"

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53920

--- 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:e46f4d7430c5210465791603735ab219ef263c51

commit r13-1544-ge46f4d7430c5210465791603735ab219ef263c51
Author: Lewis Hyatt <lhyatt@gmail.com>
Date:   Tue Jul 5 17:15:28 2022 -0400

    diagnostics: Honor #pragma GCC diagnostic in the preprocessor [PR53431]

    As discussed on PR c++/53431, currently, "#pragma GCC diagnostic" does
    not always take effect for diagnostics generated by libcpp. The reason
    is that libcpp itself does not interpret this pragma and only sends it on
    to the frontend, hence the pragma is only honored if the frontend
    arranges for it. The C frontend does process the pragma immediately
    (more or less) after seeing the token, so things work fine there. The PR
    points out that it doesn't work for C++, because the C++ frontend
    doesn't handle anything until it has read all the tokens from
    libcpp. The underlying problem is not C++-specific, though, and for
    instance, gcc -E has the same issue.

    This commit fixes the PR by adding the concept of an early pragma handler
that
    can be registered by frontends, which gives them a chance to process
    diagnostic pragmas from libcpp before it is too late for them to take
    effect. The C++ and preprocess-only frontends are modified to use early
    pragmas and correct the behavior.

    gcc/c-family/ChangeLog:

            PR preprocessor/53920
            PR c++/53431
            * c-common.cc (c_option_is_from_cpp_diagnostics): New function.
            * c-common.h (c_option_is_from_cpp_diagnostics): Declare.
            (c_pp_stream_token): Declare.
            * c-ppoutput.cc (init_pp_output): Refactor logic about skipping
            pragmas to...
            (should_output_pragmas): ...here. New function.
            (token_streamer::stream): Support handling early pragmas.
            (do_line_change): Likewise.
            (c_pp_stream_token): New function.
            * c-pragma.cc (struct pragma_diagnostic_data): New helper class.
            (pragma_diagnostic_lex_normal): New function. Moved logic for
            interpreting GCC diagnostic pragmas here.
            (pragma_diagnostic_lex_pp): New function for parsing diagnostic
pragmas
            directly from libcpp.
            (handle_pragma_diagnostic): Refactor into helper function...
            (handle_pragma_diagnostic_impl): ...here.  New function.
            (handle_pragma_diagnostic_early): New function.
            (handle_pragma_diagnostic_early_pp): New function.
            (struct pragma_ns_name): Renamed to...
            (struct pragma_pp_data): ...this.  Add new "early_handler" member.
            (c_register_pragma_1): Support early pragmas in the preprocessor.
            (c_register_pragma_with_early_handler): New function.
            (c_register_pragma): Support the new early handlers in struct
            internal_pragma_handler.
            (c_register_pragma_with_data): Likewise.
            (c_register_pragma_with_expansion): Likewise.
            (c_register_pragma_with_expansion_and_data): Likewise.
            (c_invoke_early_pragma_handler): New function.
            (c_pp_invoke_early_pragma_handler): New function.
            (init_pragma): Add early pragma support for diagnostic pragmas.
            * c-pragma.h (struct internal_pragma_handler): Add new early
handler
            members.
            (c_register_pragma_with_early_handler): Declare.
            (c_invoke_early_pragma_handler): Declare.
            (c_pp_invoke_early_pragma_handler): Declare.

    gcc/cp/ChangeLog:

            PR c++/53431
            * parser.cc (cp_parser_pragma_kind): Move earlier in the file.
            (cp_lexer_handle_early_pragma): New function.
            (cp_lexer_new_main): Support parsing and handling early pragmas.
            (c_parse_file): Adapt to changes in cp_lexer_new_main.

    gcc/testsuite/ChangeLog:

            PR preprocessor/53920
            PR c++/53431
            * c-c++-common/pragma-diag-11.c: New test.
            * c-c++-common/pragma-diag-12.c: New test.
            * c-c++-common/pragma-diag-13.c: New test.

[Bug preprocessor/53920] "gcc -E" does not honor #pragma GCC diagnostic ignored "-Wunused-macro"

[lhyatt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53920

Lewis Hyatt <lhyatt at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

--- Comment #7 from Lewis Hyatt <lhyatt at gcc dot gnu.org> ---
Fixed for GCC 13.