gcc.git/libstdc++-v3/include/std/mdspan, branch master

libstdc++: Prepare mdspan-related code for submdspan.

2025-11-20T16:21:05+00:00

The changes needed for submdspan are:

  * In submdspan related code the user-defined integer-like
    types need to be copy- and move-constructable.

  * The traits for writing tests that work with both left- and right,
    possibly padded, layouts will also be useful for submdspan.
    Therefore, this code is moved up and generalized.

  * Move __offset further up in  and fix some formatting
    mistakes.

libstdc++-v3/ChangeLog:

	* include/std/mdspan: Improve formatting and placement.
	* testsuite/23_containers/mdspan/int_like.h: Optionally,
	add move- and copy-ctors.
	* testsuite/23_containers/mdspan/layouts/padded_traits.h: Move to...
	* testsuite/23_containers/mdspan/layout_traits.h: ...here.
	* testsuite/23_containers/mdspan/layouts/ctors.cc: Fix include.
	* testsuite/23_containers/mdspan/layouts/mapping.cc: Ditto.
	* testsuite/23_containers/mdspan/layouts/padded.cc: Ditto.
	* testsuite/23_containers/mdspan/layouts/padded_neg.cc: Ditto.

Reviewed-by: Jonathan Wakely 
Reviewed-by: Tomasz Kamiński 
Signed-off-by: Luc Grosheintz

libstdc++: Make compatible with clang.

2025-11-19T14:47:11+00:00

These three changes are needed to make  compatible with Clang:

  - the type alias _Storage must occur before its first use.

  - the friend declarations of function must match exactly, including
  noexcept and constexpr.

  - the 'template' in typename T::template type.

libstdc++-v3/ChangeLog:

	* include/std/mdspan (extents::_Storage): Move type alias before
	its first use.
	(__mdspan::__static_extents): Add missing noexcept and constexpr
	to friend declaration in extents.
	(__mdspan::__dynamic_extents): Ditto.

Reviewed-by: Jonathan Wakely 
Signed-off-by: Luc Grosheintz

libstdc++: Implement submdspan_mapping_result. [PR110352]

2025-10-08T10:39:44+00:00

Implement the class submdspan_mapping_result and add it to the std
module.

	PR libstdc++/110352

libstdc++-v3/ChangeLog:

	* include/std/mdspan (submdspan_mapping_result): New class.
	* src/c++23/std.cc.in (submdspan_mapping_result): Add.

Reviewed-by: Jonathan Wakely 
Reviewed-by: Tomasz Kamiński 
Signed-off-by: Luc Grosheintz

libstdc++: Implement full_extent_t. [PR110352]

2025-10-08T10:35:19+00:00

Add the class and updates the std module.

	PR libstdc++/110352

libstdc++-v3/ChangeLog:

	* include/std/mdspan (full_extent_t): New class.
	* src/c++23/std.cc.in (full_extent_t): Add.

Reviewed-by: Jonathan Wakely 
Reviewed-by: Tomasz Kamiński 
Signed-off-by: Luc Grosheintz

libstdc++: Implement strided_slice from . [PR110352]

2025-10-08T10:32:17+00:00

Adds strided_slice as standardized in N5014. Also creates
the internal feature testing macro for submdspan.

	PR libstdc++/110352

libstdc++-v3/ChangeLog:

	* include/bits/version.def (submdspan): New internal macro.
	* include/bits/version.h: Regenerate.
	* include/std/mdspan (strided_slice): New class.
	* src/c++23/std.cc.in (strided_slice): Add.
	* testsuite/23_containers/mdspan/submdspan/strided_slice.cc: New test.
	* testsuite/23_containers/mdspan/submdspan/strided_slice_neg.cc: New test.

Reviewed-by: Jonathan Wakely 
Reviewed-by: Tomasz Kamiński 
Signed-off-by: Luc Grosheintz

libstdc++: Improve and cleanup mdspan related code.

2025-10-08T10:30:51+00:00

The improvement is that in __index_type_cast, we don't need to check at
runtime if we know that _IndexType is smaller than _OIndexType.

The cleanup is whitespace (overlength lines) in , grouping is_always_foo
and is_foo together, and de-uglifying a variable in test code.

libstdc++-v3/ChangeLog:

	* include/std/mdspan (__mdspan::__index_type_cast): Optimize by
	skipping a __glibcxx_assert if it's know at compile-time.
	(std::layout_left_padded, std::layout_righ_padded): Reorder
	is_always_strided and is_unique member functions.
	* testsuite/23_containers/mdspan/int_like.h: Rename _M_i to
	value.

Reviewed-by: Jonathan Wakely 
Reviewed-by: Tomasz Kamiński 
Signed-off-by: Luc Grosheintz

libstdc++: Implement std::layout_right_padded [PR110352].

2025-10-08T09:35:43+00:00

This commit adds the right padded layout as described in N5014, with
LWG4372 (dynamic padding value) and LWG4314 (move in operator()).

	PR libstdc++/110352

libstdc++-v3/ChangeLog:

	* include/std/mdspan (_RightPaddedIndices): Traits for right
	padded layouts.
	(layout_right::mapping::mapping) New overload for right padded
	layouts.
	(layout_right_padded): Add implementation.
	* src/c++23/std.cc.in (layout_right_padded): Add.
	* testsuite/23_containers/mdspan/layouts/ctors.cc: Update
	test for right padded layouts.
	* testsuite/23_containers/mdspan/layouts/empty.cc: Ditto.
	* testsuite/23_containers/mdspan/layouts/mapping.cc: Ditto.
	* testsuite/23_containers/mdspan/layouts/padded.cc: Ditto.
	* testsuite/23_containers/mdspan/layouts/padded_neg.cc: Ditto.
	* testsuite/23_containers/mdspan/layouts/padded_traits.h: Ditto.

Reviewed-by: Tomasz Kamiński 
Signed-off-by: Luc Grosheintz

libstdc++: Implement std::layout_left_padded [PR110352].

2025-10-08T09:22:32+00:00

This commit adds a new layout layout_left_padded as standardized in
N5014. It adds a purely internal feature testing macro padded_layouts
and registers layout_left_padded in the std module.

This commit implements LWG4372, because without it's not possible
to properly test padded layouts with a dynamic padding value. It also
implements LWG4314, for consistency with prior layouts.

The implementation uses a _PaddedStorage to deduplicate most of the code
shared between left- and right-padded layouts. It's implemented through
aggregation rather than inheritence, because of a bug related to
inheriting conditionally explicit ctors.

The tests are written such that the canonical version works for
layout_left_padded. A version for layout_right_padded is derived
essentially by reversing the order of the extents.

	PR libstdc++/110352

libstdc++-v3/ChangeLog:

	* include/bits/version.def (padded_layouts): Add new internal
	feature testing macro.
	* include/bits/version.h: Regenerate.
	* include/std/mdspan (__fwd_prod): New overload.
	(layout_left_padded): Add declaration and implementation.
	(layout_right_padded): Add declaration only.
	(layout_left::mapping::mapping): New overload for left
	padded mappings.
	(__index_type_cast): New function that performs a checked cast
	to index_type.
	(__is_left_padded_mapping): New concept.
	(__is_right_padded_mapping): Ditto.
	(__standardized_mapping): Recognize left and right padded
	mappings.
	(_LeftPaddedIndices): Traits for left padded details.
	(_PaddedStorage): New class for implementing padded layouts.
	* src/c++23/std.cc.in (layout_left_padded): Add.
	* testsuite/23_containers/mdspan/layouts/class_mandate_neg.cc:
	Refactor and add tests for layout_left_padded.
	* testsuite/23_containers/mdspan/layouts/ctors.cc: Ditto.
	* testsuite/23_containers/mdspan/layouts/empty.cc: Ditto.
	* testsuite/23_containers/mdspan/layouts/mapping.cc: Ditto.
	* testsuite/23_containers/mdspan/layouts/padded.cc: Ditto.
	* testsuite/23_containers/mdspan/layouts/padded_neg.cc: Ditto.
	* testsuite/23_containers/mdspan/layouts/padded_traits.h: New
	traits.

Reviewed-by: Tomasz Kamiński 
Signed-off-by: Luc Grosheintz

libstdc++: Refactor mdspan::static_quotient.

2025-09-25T13:55:43+00:00

For padded layouts we want to check that the product of the
padded stride with the remaining extents is representable.

Creating a second overload, allows passing in subspans of the
static extents and retains the ergonomics for the common case
of passing in all static extents.

libstdc++-v3/ChangeLog:

	* include/std/mdspan (__static_quotient): New overload.

Reviewed-by: Tomasz Kamiński 
Reviewed-by: Jonathan Wakely 
Signed-off-by: Luc Grosheintz

libstdc++: Rename _S-prefixed identifiers in .

2025-09-10T10:51:38+00:00

In libstdc++ the prefix _S is used for static members only. In 
there's several type aliases that also used the prefix _S. They now use
a single leading underscore follow by a capital letter instead.

libstdc++-v3/ChangeLog:

	* include/std/mdspan (_ExtentsStorage::_Base): New name for
	_S_base.
	(_ExtentsStorage::_Storage): New name for _S_storage.
	(extents::_Storage): New name for _S_storage.
	(layout_stride::mapping::_Strides): New name for
	_S_stries_t.
	* testsuite/23_containers/mdspan/class_mandate_neg.cc: Update
	test to the new error message.

Reviewed-by: Jonathan Wakely 
Signed-off-by: Luc Grosheintz