[Bug libstdc++/97869] defines __cpp_lib_span even when doesn't provide an implementation

[cvs-commit at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97869

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jonathan Wakely
<r...@gcc.gnu.org>:

https://gcc.gnu.org/g:992643655c872f8332f9e8e453631a8fad52943a

commit r10-9044-g992643655c872f8332f9e8e453631a8fad52943a
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Tue Nov 17 15:26:29 2020 +0000

    libstdc++: Fix unconditional definition of __cpp_lib_span in <version> [PR
97869}

    The <span> header is empty unless Concepts are supported, but <version>
    defines the __cpp_lib_span feature test macro unconditionally. It should
    be guarded by the same conditions as in <span>.

    libstdc++-v3/ChangeLog:

            PR libstdc++/97869
            * include/precompiled/stdc++.h: Include <coroutine>.
            * include/std/version (__cpp_lib_span): Check __cpp_lib_concepts
            before defining.

    (cherry picked from commit ecf65330c11544ebf35e198087b4a42be089c620)