How would you like to track this on bugzilla: 1. As part of submdspan: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110352 https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2630r4.html
2. As a new issue, because it's a different paper: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2897r7.html On 7/3/25 12:33, Luc Grosheintz wrote:
This patch series implements the aligned_accessor paper P2897R7 in three parts: - Implement `is_sufficiently_aligned` which is part of <memory>. - Prepare the accessor tests for reuse. - Implement aligned_accessor. A couple of remarks: - The paper P2897R7 and spec N5008 don't specify that the aligment for is_sufficiently_aligned must be a power of two. - The reasoning for why is_sufficiently_aligned isn't constexpr is nicely described in the paper. - Use of `class` in is_sufficiently_aligned is for consistency within that file. - The tests create new unsupported tests and expected failures. The testsuite doesn't have all that many of those; so there's likely a strategy to avoid this. However, I don't know how. - These changes are independent of mdspan, but due to the precise location of the code it might conflict with the mdspan patch series. - I skipped updating `cxxapi-data.csv` for is_sufficiently_aligned due to consistency with the rest of the mdspan patches, i.e. there will be a bulk update of the file later. - Each commit was tested with/without PCH and with/without _GLIBCXX_DEBUG filtered by 20_util/is_sufficiently_aligned and 23_containers/mdspan. The last commit was tested fully with/without PCH. All tests on x86_64-linux. As always I'm happy to reorganize into different commits, if the grouping doesn't make sense. Luc Grosheintz (3): libstdc++: Implement is_sufficiently_aligned. libstdc++: Prepare test code for default_accessor for reuse. libstdc++: Implement aligned_accessor from mdspan. libstdc++-v3/include/bits/align.h | 16 ++ libstdc++-v3/include/bits/version.def | 18 ++ libstdc++-v3/include/bits/version.h | 20 +++ libstdc++-v3/include/std/mdspan | 72 ++++++++ libstdc++-v3/include/std/memory | 1 + libstdc++-v3/src/c++23/std.cc.in | 4 +- .../20_util/is_sufficiently_aligned/1.cc | 31 ++++ .../20_util/is_sufficiently_aligned/2.cc | 7 + .../23_containers/mdspan/accessors/aligned.cc | 43 +++++ .../mdspan/accessors/aligned_ftm.cc | 6 + .../mdspan/accessors/aligned_neg.cc | 33 ++++ .../accessors/debug/aligned_access_neg.cc | 23 +++ .../accessors/debug/aligned_offset_neg.cc | 23 +++ .../23_containers/mdspan/accessors/default.cc | 99 ----------- .../23_containers/mdspan/accessors/generic.cc | 168 ++++++++++++++++++ 15 files changed, 464 insertions(+), 100 deletions(-) create mode 100644 libstdc++-v3/testsuite/20_util/is_sufficiently_aligned/1.cc create mode 100644 libstdc++-v3/testsuite/20_util/is_sufficiently_aligned/2.cc create mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/aligned.cc create mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/aligned_ftm.cc create mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/aligned_neg.cc create mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/debug/aligned_access_neg.cc create mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/debug/aligned_offset_neg.cc delete mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/default.cc create mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/generic.cc
