<div dir="ltr">I have created a separate bugzilla for it: <a href="https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120994">https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120994</a></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Tue, Jul 8, 2025 at 9:58 AM Luc Grosheintz <<a href="mailto:luc.grosheintz@gmail.com">luc.grosheintz@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">How would you like to track this on bugzilla:<br>
<br>
   1. As part of submdspan:<br>
   <a href="https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110352" rel="noreferrer" target="_blank">https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110352</a><br>
   <a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2630r4.html" rel="noreferrer" target="_blank">https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2630r4.html</a><br>
<br>
   2. As a new issue, because it's a different paper:<br>
   <a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2897r7.html" rel="noreferrer" target="_blank">https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2897r7.html</a><br>
<br>
On 7/3/25 12:33, Luc Grosheintz wrote:<br>
> This patch series implements the aligned_accessor paper P2897R7 in three<br>
> parts:<br>
> <br>
>    - Implement `is_sufficiently_aligned` which is part of <memory>.<br>
>    - Prepare the accessor tests for reuse.<br>
>    - Implement aligned_accessor.<br>
> <br>
> A couple of remarks:<br>
> <br>
>    - The paper P2897R7 and spec N5008 don't specify that the aligment<br>
>    for is_sufficiently_aligned must be a power of two.<br>
> <br>
>    - The reasoning for why is_sufficiently_aligned isn't constexpr is<br>
>    nicely described in the paper.<br>
> <br>
>    - Use of `class` in is_sufficiently_aligned is for consistency within<br>
>    that file.<br>
> <br>
>    - The tests create new unsupported tests and expected failures. The<br>
>    testsuite doesn't have all that many of those; so there's likely a<br>
>    strategy to avoid this. However, I don't know how.<br>
> <br>
>    - These changes are independent of mdspan, but due to the precise<br>
>    location of the code it might conflict with the mdspan patch series.<br>
> <br>
>    - I skipped updating `cxxapi-data.csv` for is_sufficiently_aligned<br>
>    due to consistency with the rest of the mdspan patches, i.e. there<br>
>    will be a bulk update of the file later.<br>
> <br>
>    - Each commit was tested with/without PCH and with/without<br>
>    _GLIBCXX_DEBUG filtered by 20_util/is_sufficiently_aligned<br>
>    and 23_containers/mdspan.<br>
>    The last commit was tested fully with/without PCH. All tests on<br>
>    x86_64-linux.<br>
> <br>
> As always I'm happy to reorganize into different commits, if the<br>
> grouping doesn't make sense.<br>
> <br>
> Luc Grosheintz (3):<br>
>    libstdc++: Implement is_sufficiently_aligned.<br>
>    libstdc++: Prepare test code for default_accessor for reuse.<br>
>    libstdc++: Implement aligned_accessor from mdspan.<br>
> <br>
>   libstdc++-v3/include/bits/align.h             |  16 ++<br>
>   libstdc++-v3/include/bits/version.def         |  18 ++<br>
>   libstdc++-v3/include/bits/version.h           |  20 +++<br>
>   libstdc++-v3/include/std/mdspan               |  72 ++++++++<br>
>   libstdc++-v3/include/std/memory               |   1 +<br>
>   libstdc++-v3/src/c++23/<a href="http://std.cc.in" rel="noreferrer" target="_blank">std.cc.in</a>              |   4 +-<br>
>   .../20_util/is_sufficiently_aligned/1.cc      |  31 ++++<br>
>   .../20_util/is_sufficiently_aligned/2.cc      |   7 +<br>
>   .../23_containers/mdspan/accessors/aligned.cc |  43 +++++<br>
>   .../mdspan/accessors/aligned_ftm.cc           |   6 +<br>
>   .../mdspan/accessors/aligned_neg.cc           |  33 ++++<br>
>   .../accessors/debug/aligned_access_neg.cc     |  23 +++<br>
>   .../accessors/debug/aligned_offset_neg.cc     |  23 +++<br>
>   .../23_containers/mdspan/accessors/default.cc |  99 -----------<br>
>   .../23_containers/mdspan/accessors/generic.cc | 168 ++++++++++++++++++<br>
>   15 files changed, 464 insertions(+), 100 deletions(-)<br>
>   create mode 100644 libstdc++-v3/testsuite/20_util/is_sufficiently_aligned/1.cc<br>
>   create mode 100644 libstdc++-v3/testsuite/20_util/is_sufficiently_aligned/2.cc<br>
>   create mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/aligned.cc<br>
>   create mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/aligned_ftm.cc<br>
>   create mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/aligned_neg.cc<br>
>   create mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/debug/aligned_access_neg.cc<br>
>   create mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/debug/aligned_offset_neg.cc<br>
>   delete mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/default.cc<br>
>   create mode 100644 libstdc++-v3/testsuite/23_containers/mdspan/accessors/generic.cc<br>
> <br>
<br>
</blockquote></div>