https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77330
--- Comment #4 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- When there isn't whole-implementation, including library, support for the types as "basic types" (see the resolution to DR#445), you need to consider them as some other kind of type, analogous to vector types, for which you need to use aligned_alloc (or posix_memalign etc.) just as with vector types (if you'd used __m512 in place of __float128, for example). But I say that unlike vector types, _Decimal128 and _Float128 *should* be considered basic types, and so glibc, supporting being used together with libdfp, *should* have the malloc alignment increased accordingly and this should be considered a glibc bug (which is no longer hard to fix thanks to the work done to fix malloc alignment on powerpc32). It's always the case that however you construct a pointer to a type, it's your responsibility to ensure that it's appropriately aligned for that type, which means 16-byte-aligned for a structure containing __float128; it's not GCC's responsibility to second-guess whether your code really ensures that. If there are 16-byte-aligned basic types, malloc is an appropriate means of ensuring that and it's a malloc bug not to provide such alignment. When 16-byte-alignment is not a fundamental alignment requirement, malloc is not an appropriate means and using malloc there is a bug in the program using malloc for such an allocation.
