Re: Alignment issue?

[Richard Frith-Macdonald]

On 5 Jul 2013, at 14:41, Laurent Michel <address@hidden> wrote:

> Ok, so that's a bug then. On x64, one should add 8 bytes of padding before 
> (or after) the counter in front of any NSObject to preserve a clean 
> alignment. 

NSAllocateObject() already contained code to do that, but was getting it wrong 
using the alignment of double.
With gcc it can use __BIGGEST_ALIGNMENT__ to get the right calculation, but 
that's not available with clang.
So I changed the code in svn trunk to always use 16 if we are compiling with 
clang.

If anyone knows a clang equiivalent of __BIGGEST_ALIGNMENT__, we could/should 
change to use it, since using 16 may waste space on some architectures and may 
not be enough on others (though I know of none).

PS. this is for NSAllocateObject() ... if you call class_createInstance() then 
the runtime will probably not provide the required padding :-(

However, if you are using the old runtime, the compatibility layer in 
gnustep-base now implements  class_createInstance() by calling 
NSDAllocateObject(), so in this case it should be safe to use that runtime 
function.