On Tue, 18 Aug 2015, john smith wrote: > On Tue, Aug 18, 2015 at 5:50 PM, Segher Boessenkool > <segher@xxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, Aug 18, 2015 at 05:04:28PM +0200, john smith wrote: > >> In gcc manual it says: > >> > >> "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". > I guess 6.2.5 subclause 25 together with note 39 (interchangeablity) would result in "perfect multiple of the lowest common multiple" see also 6.2.5 subclause 20 on derived types. thx! hofrat
