[Bug libstdc++/97549] [11 Regression] include/pstl rebase breaking <execution>

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97549

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:7e647d71d556b73e84f4edd0733bcc83bc70ae1e

commit r11-7339-g7e647d71d556b73e84f4edd0733bcc83bc70ae1e
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Tue Feb 23 09:26:23 2021 +0100

    libstdc++: Fix up parallel_backend_serial.h [PR97549]

    In GCC 10, parallel_backend.h just included parallel_backend_{serial,tbb}.h
and
    did nothing beyond that, and parallel_backend_tbb.h provided directly
    namespace __pstl { namespace __par_backend { ... } }
    and defined everything in there, while parallel_backend_serial.h did:
    namespace __pstl { namespace __serial { ... } } and had this
    namespace __pstl { namespace __par_backend { using namespace
__pstl::__serial; } }
    at the end.
    In GCC 11, parallel_backend.h does:
    namespace __pstl { namespace __par_backend = __serial_backend; }
    after including parallel_backend_serial.h or
    namespace __pstl { namespace __par_backend = __tbb_backend; }
    after including parallel_backend_tbb.h.  The latter then has:
    namespace __pstl { namespace __tbb_backend { ... } }
    and no using etc. at the end, while parallel_backend_serial.h changed to:
    namespace __pstl { namespace __serial_backend { ... } }
    but has this leftover block from the GCC 10 times.  Even changing that
    using namespace __pstl::__serial;
    to
    using namespace __pstl::__serial_backend;
    doesn't work, as it clashes with
    namespace __pstl { namespace __par_backend = __serial_backend; }
    in parallel_backend.h.

    2021-02-23  Jakub Jelinek  <jakub@redhat.com>

            PR libstdc++/97549
            * include/pstl/parallel_backend_serial.h: Remove
__pstl::__par_backend.