https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65122
--- Comment #4 from Marc Glisse <glisse at gcc dot gnu.org> --- (In reply to Benoit Jacob from comment #3) > I'd be interested in an explanation of why the default STL allocator can't > just honor the alignment of the value_type ? [allocator.members] "It is implementation-defined whether over-aligned types are supported" so we don't really have to. "the storage is obtained by calling ::operator new(std::size_t)" so we can't use posix_memalign (providing a separate allocator that does could be a good idea though). We could, when the type is over-aligned, do the usual trick of requesting too much memory so we have enough margin to find a suitably aligned region inside, and write a marker before so we remember where the real allocation started. That might be what was tried in PR55727 (I didn't check), the maintainers might be ok with this if someone posts a patch. But calling new T would still be broken. It seems better in the long term to add the aligned versions of operator new and make both new and std::allocator use those (in the standard). Note that there would be ABI issues switching from the trick in the previous paragraph to this.
