On Tue, Aug 18, 2015 at 05:57:36PM +0200, john smith wrote: > >> "Note that the alignment of any given struct or union type is required > >> by the ISO C standard to be at least a perfect multiple of the lowest > >> common multiple of the alignments of all of the members of the struct > >> or union in question." > >> > >> Where exactly is this requirement mentioned in C standard? I was > >> looking for it in both C99 and C11 drafts and couldn't find it. > > > > C99 6.7.2.1/12 ? > > It just says that "Each non-bit-field member of a structure or union > object is aligned in an implementation-defined manner appropriate to > its type.". It doesn't require an overall alignment of the structure > to be "at least a perfect multiple of the lowest common multiple of > the alignments of all of the members of the struct". If the alignment of any member of the struct is A, the alignment of the struct has to be a multiple of A (by the above, and the definition of alignment). Now consider all members together, and you get what the GCC manual says. Segher
