Found while running libc++'s test suite with MSVC's STL.
* I've filed [LWG-4021](https://cplusplus.github.io/LWG/issue4021)
"`mdspan::is_always_meow()` should be `noexcept`" and implemented this
in libc++'s product and test code.
* Use `LIBCPP_STATIC_ASSERT` to avoid issues with `noexcept`
strengthening in MSVC's STL.
+ As permitted by the Standard, MSVC's STL conditionally strengthens
`mdspan` construction/`is_meow`/`stride` and `elements_view` iterator
`base() &&`, and always strengthens `basic_stringbuf` `swap`.
+ In `mdspan/properties.pass.cpp`, this also upgrades runtime `assert`s
to `static_assert`s.
* Improvement: Upgrade `assert` to `static_assert` when inspecting the
`noexcept`ness of `std::ranges::iter_move`. (These `!noexcept` tests
weren't causing issues for MSVC's STL, so I didn't change them to be
libc++-specific.)
This implements layout_stride for C++23 and with that completes the
implementation of the C++23 mdspan header. The feature test macro is
added, and the status pages updated.
Co-authored-by: Damien L-G <dalg24@gmail.com>
Differential Revision: https://reviews.llvm.org/D157171
This implements P0009 std::mdspan ((https://wg21.link/p0009)),
a multidimensional span with customization points for
layouts and data access.
Co-authored-by: Damien L-G <dalg24@gmail.com>
Differential Revision: https://reviews.llvm.org/154367
This commit implements default_accessor in support of C++23 mdspan
(https://wg21.link/p0009). default_accessor is the trivial accessor
using plain pointers and reference to element types.
Co-authored-by: Damien L-G <dalg24@gmail.com>
Differential Revision: https://reviews.llvm.org/D153935
This commit implements layout_left in support of C++23 mdspan
(https://wg21.link/p0009). layout_left is a layout mapping policy
whose index mapping corresponds to the memory layout of Fortran arrays.
Thus the left most index has stride-1 access, and the right most index
is associated with the largest stride.
Co-authored-by: Damien L-G <dalg24@gmail.com>
Differential Revision: https://reviews.llvm.org/D153783
This commit implements layout_right in support of C++23 mdspan
(https://wg21.link/p0009). layout_right is a layout mapping policy
whose index mapping corresponds to the memory layout of multidimensional
C-arrays, and is thus also referred to as the C-layout.
Co-authored-by: Damien L-G <dalg24@gmail.com>
Differential Revision: https://reviews.llvm.org/D151267
This patch adds std::extents. extents is one of the core classes used by std::mdspan. It describes a multi-dimensional index space with a mix of compile time and runtime sizes. Furthermore, it is templated on the index type used to describe the multi-dimensional index space.
The class is designed to be highly optimizable in performance critical code sections, and is fully useable in constant expressions contexts.
Testing of this class tends to be somewhat combinatorical, due to the large number of possible corner cases involved in situations where we have both runtime and compile time extents. To add to this, the class is designed to be interoperable (in particular constructible) from arguments which only need to be convertible to the index_type, but are otherwise arbitrary user types. For a larger discussion on the design of this class refer to: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p0009r18.html
Co-authored-by: Damien L-G <dalg24@gmail.com>
Reviewed By: ldionne, #libc
Spies: libcxx-commits, H-G-Hristov, tschuett, philnik, arichardson, Mordante, crtrott
Differential Revision: https://reviews.llvm.org/D148067
