(top-posting fixed) Maurizio Vitale writes: > > On Dec 21, 2006, at 4:23 PM, Tim Prince wrote: > > > Maurizio Vitale wrote: > >> Thanks. Now to add to my confusion, on my system __alignof(long > >> double) returns 16, which I presume means that all allocation, > >> static, dynamic and automatic for long double objects are 16 byte > >> aligned. > > > > This is a reasonable choice, that long doubles would be aligned for > > good performance, unless the alignment is over-ridden by a packed > > or reduced alignment specification. > > It is certainly reasonable, but if it is true it means that the > compiler is capable on linux, x86_64 to impose a 16 byte alignment on > some object for all type of allocations. Then I would expect an > __attribute__ ((aligned (16)) for a user defined type to be obeyed as > well. > > I haven't tested whether long doubles are actually allocated on 16 > byte boundaries in all case (global, auto and dynamic), mainly > because the tests would be inconclusive, unless you see an alignment > < 16. > > I just mentioned the data point to see if it did say anything to GCC > developers. Well, we don't know what question you're trying to ask. If you can be specific, we'll give you an answer. Andrew.
