On Tue, 20 Aug 2019, "Markus Fröschle" wrote: > Thank you (and others) for your answers. Now I'm just as smart as before, > however. > > Is it a supported, documented, 'long term' feature we can rely on or not? > > If yes, I would expect it to be properly documented. If not, never mind.
I think it's properly documented in gcc-9: https://gcc.gnu.org/onlinedocs/gcc-9.2.0/gcc/Common-Type-Attributes.html (the "old" behavior where the compiler would neither honor reduced alignment nor issue a warning seems questionable, the new documentation promises a more sensible approach) In portable code one can also use memcpy to move unaligned data, the compiler should translate it like an unaligned load/store when size is a suitable constant: int val; memcpy(&val, ptr, sizeof val); (or __builtin_memcpy when -ffreestanding is in effect) Alexander
