This is the second version of:
https://gcc.gnu.org/pipermail/libstdc++/2025-April/060914.html
Following the comments from Jonathan, I reorganized the tests. Using the
very effective tricks pointed out by Tomasz, led to a much more concise
implementation of `_ExtentsStorage`. If desired, this could be taken
further and the helper `_ExtentsStorage` could be completely merged into
`extents`.
Changes since v1:
* All `_neg` tests are replaced by `static_assert`s. Additionally,
some other small tests are merged into related files.
* Assigning the elements of `_M_dynamic_extents` in a for loop,
eliminates the need for `index_sequence`.
* The `consteval` trick enables removing all template meta-programming
helpers needed to create `_S_dynamic_index{,_inv}`.
* The trick to use `initializer_list` removes the need for the ctor
`_ExtentsStorage(Integrals...)`.
* Introduces a concept for checking if `_OIndexType` is suitable, i.e.
convertible & nothrow constructible; and replaces `typename` with
the concept.
* The internal namespace for details is renamed to `__mdspan`.
* Regenerates `include/bits/version.h` to respect `no_stdname`.
* Fixes the bug in `extents::size_type`.
* Changes the integer conversion `_M_int_cast` as suggested.
* Fixed `#include <mdspan>` in `precompiled/stdc++.h`.
* Replaced the `array<IndexType, N>` used for storing the dynamic
extents with to a custom type `__mdspan::__array`. See Point 2
below.
I'd like to point out the following:
1. When calling the ctor `extents<int, 1, 2>(IntLike{}, IntLike{})` the
user-defined conversion operator of `IntLike` will be called twice
when creating the `initializer_list`, even though ultimately we don't
need either of the two values, because both extents are static.
2. In v1 the implementation used `array<Int, 0>` to store the dynamic
extents when there are none. Therefore, `[[no_unique_address]]` had
no effect. In v2, I've replaced the `array<Int, N>` with a custom type
that works with `[[no_unique_address]]`.
The patches where tested with `make check-target-libstdc++-v3`.
Thank you Tomasz Kaminski and Jonathan Wakely for your helpful review!
Luc Grosheintz (4):
libstdc++: Setup internal FTM for mdspan.
libstdc++: Add header mdspan to the build-system.
libstdc++: Implement std::extents [PR107761].
libstdc++: Add tests for std::extents.
libstdc++-v3/doc/doxygen/user.cfg.in | 1 +
libstdc++-v3/include/Makefile.am | 1 +
libstdc++-v3/include/Makefile.in | 1 +
libstdc++-v3/include/bits/version.def | 9 +
libstdc++-v3/include/bits/version.h | 9 +
libstdc++-v3/include/precompiled/stdc++.h | 1 +
libstdc++-v3/include/std/mdspan | 352 ++++++++++++++++++
libstdc++-v3/src/c++23/std.cc.in | 6 +-
.../23_containers/mdspan/extents/assign.cc | 29 ++
.../mdspan/extents/class_properties.cc | 62 +++
.../23_containers/mdspan/extents/ctor_copy.cc | 75 ++++
.../mdspan/extents/ctor_copy_constexpr.cc | 20 +
.../23_containers/mdspan/extents/ctor_ints.cc | 58 +++
.../mdspan/extents/ctor_ints_constexpr.cc | 12 +
.../mdspan/extents/ctor_shape_all_extents.cc | 61 +++
.../mdspan/extents/ctor_shape_constexpr.cc | 23 ++
.../extents/ctor_shape_dynamic_extents.cc | 91 +++++
.../mdspan/extents/custom_integer.cc | 87 +++++
.../mdspan/extents/deduction_guide.cc | 34 ++
.../23_containers/mdspan/extents/dextents.cc | 11 +
.../23_containers/mdspan/extents/extent.cc | 24 ++
.../23_containers/mdspan/extents/ops_eq.cc | 58 +++
22 files changed, 1024 insertions(+), 1 deletion(-)
create mode 100644 libstdc++-v3/include/std/mdspan
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/assign.cc
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/class_properties.cc
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/ctor_copy.cc
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/ctor_copy_constexpr.cc
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/ctor_ints.cc
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/ctor_ints_constexpr.cc
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/ctor_shape_all_extents.cc
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/ctor_shape_constexpr.cc
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/ctor_shape_dynamic_extents.cc
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/custom_integer.cc
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/deduction_guide.cc
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/dextents.cc
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/extent.cc
create mode 100644
libstdc++-v3/testsuite/23_containers/mdspan/extents/ops_eq.cc
--
2.48.1
