[PATCH v1 2/4] libstdc++: Add header mdspan to the build-system.

[Jonathan Wakely]

On Wed, 9 Apr 2025, 08:25 Luc Grosheintz, <luc.grosheintz@gmail.com> wrote:

> Creates a nearly empty header mdspan and adds it to the build-system and
> Doxygen config file.
>

Nice, thanks! I'll look at these patches properly another time (I'm
unavailable today) but one quick comment below ...



> libstdc++-v3/ChangeLog:
>
>         * doc/doxygen/user.cfg.in: Add <mdspan>.
>         * include/Makefile.am: Ditto.
>         * include/Makefile.in: Ditto.
>         * include/precompiled/stdc++.h: Ditto.
>         * include/std/mdspan: New file.
>
> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
> ---
>  libstdc++-v3/doc/doxygen/user.cfg.in      |  1 +
>  libstdc++-v3/include/Makefile.am          |  1 +
>  libstdc++-v3/include/Makefile.in          |  1 +
>  libstdc++-v3/include/precompiled/stdc++.h |  4 ++
>  libstdc++-v3/include/std/mdspan           | 48 +++++++++++++++++++++++
>  5 files changed, 55 insertions(+)
>  create mode 100644 libstdc++-v3/include/std/mdspan
>
> diff --git a/libstdc++-v3/doc/doxygen/user.cfg.in
> b/libstdc++-v3/doc/doxygen/user.cfg.in
> index ae50f6dd0c7..be42ea5d6b1 100644
> --- a/libstdc++-v3/doc/doxygen/user.cfg.in
> +++ b/libstdc++-v3/doc/doxygen/user.cfg.in
> @@ -878,6 +878,7 @@ INPUT                  = @srcdir@/doc/doxygen/doxygroups.cc
> \
>                           include/list \
>                           include/locale \
>                           include/map \
> +                         include/mdspan \
>                           include/memory \
>                           include/memory_resource \
>                           include/mutex \
> diff --git a/libstdc++-v3/include/Makefile.am
> b/libstdc++-v3/include/Makefile.am
> index 537774c2668..1140fa0dffd 100644
> --- a/libstdc++-v3/include/Makefile.am
> +++ b/libstdc++-v3/include/Makefile.am
> @@ -38,6 +38,7 @@ std_freestanding = \
>         ${std_srcdir}/generator \
>         ${std_srcdir}/iterator \
>         ${std_srcdir}/limits \
> +       ${std_srcdir}/mdspan \
>         ${std_srcdir}/memory \
>         ${std_srcdir}/numbers \
>         ${std_srcdir}/numeric \
> diff --git a/libstdc++-v3/include/Makefile.in
> b/libstdc++-v3/include/Makefile.in
> index 7b96b2207f8..c96e981acd6 100644
> --- a/libstdc++-v3/include/Makefile.in
> +++ b/libstdc++-v3/include/Makefile.in
> @@ -396,6 +396,7 @@ std_freestanding = \
>         ${std_srcdir}/generator \
>         ${std_srcdir}/iterator \
>         ${std_srcdir}/limits \
> +       ${std_srcdir}/mdspan \
>         ${std_srcdir}/memory \
>         ${std_srcdir}/numbers \
>         ${std_srcdir}/numeric \
> diff --git a/libstdc++-v3/include/precompiled/stdc++.h
> b/libstdc++-v3/include/precompiled/stdc++.h
> index 1ffde3ed450..56c480b6203 100644
> --- a/libstdc++-v3/include/precompiled/stdc++.h
> +++ b/libstdc++-v3/include/precompiled/stdc++.h
> @@ -237,6 +237,10 @@
>  #include <stdfloat>
>  #endif
>
> +#if __cpluslus >= 202207L
>

Typo in the macro name here.

+#include <mdspan>
> +#endif
> +
>  #if __cplusplus > 202302L
>  #include <text_encoding>
>  #endif
> diff --git a/libstdc++-v3/include/std/mdspan
> b/libstdc++-v3/include/std/mdspan
> new file mode 100644
> index 00000000000..4094a416d1e
> --- /dev/null
> +++ b/libstdc++-v3/include/std/mdspan
> @@ -0,0 +1,48 @@
> +// <mdspan> -*- C++ -*-
> +
> +// Copyright (C) 2025 Free Software Foundation, Inc.
> +//
> +// This file is part of the GNU ISO C++ Library.  This library is free
> +// software; you can redistribute it and/or modify it under the
> +// terms of the GNU General Public License as published by the
> +// Free Software Foundation; either version 3, or (at your option)
> +// any later version.
> +
> +// This library is distributed in the hope that it will be useful,
> +// but WITHOUT ANY WARRANTY; without even the implied warranty of
> +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +// GNU General Public License for more details.
> +
> +// Under Section 7 of GPL version 3, you are granted additional
> +// permissions described in the GCC Runtime Library Exception, version
> +// 3.1, as published by the Free Software Foundation.
> +
> +// You should have received a copy of the GNU General Public License and
> +// a copy of the GCC Runtime Library Exception along with this program;
> +// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
> +// <http://www.gnu.org/licenses/>.
> +
> +/** @file mdspan
> + *  This is a Standard C++ Library header.
> + */
> +
> +#ifndef _GLIBCXX_MDSPAN
> +#define _GLIBCXX_MDSPAN 1
> +
> +#ifdef _GLIBCXX_SYSHDR
> +#pragma GCC system_header
> +#endif
> +
> +#define __glibcxx_want_mdspan
> +#include <bits/version.h>
> +
> +#ifdef __glibcxx_mdspan
> +
> +namespace std _GLIBCXX_VISIBILITY(default)
> +{
> +_GLIBCXX_BEGIN_NAMESPACE_VERSION
> +
> +_GLIBCXX_END_NAMESPACE_VERSION
> +}
> +#endif
> +#endif
> --
> 2.49.0
>
>
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