Re: ABI Compatibility (was Re: Installation woes for the average user...)

[Xavier Glattard]

Riccardo Mottola a écrit :
(...)
> David Chisnall wrote:
(...)
> Yes, this appears to me the "least hurting" path. But I laready dislike.
> If we really need, this should be the road.
> > If you make private ivars into a structure and make a pointer to this
> > an ivar, you add an extra malloc for every +alloc (expensive) and you
> > add an extra load for ever ivar access.
>
> That is an abomination.

Another stupid question : the memory allocation function accepts an 
'extraBytes' parameter. These bytes are allocated _after_ the instance 
bytes by the same 'malloc' call. Couldn't this system be adapted to ivar 
storage ? The extra storage is at self+1 : no need for an additional 
pointer, and no extra load for ivar access.

@interface NSObject (ExtraMemory)
+ (id) allocWithZone: (NSZone*)zone extra: (size_t) extraBytes;
@end

---- Usage

typedef
struct _LibraryClass_ext_st
{
  int ivar1;
  int ivar2;
} _LibraryClass_ext;

#define LIBRARYCLASS_EXTRA(obj) ((_LibraryClass_ext*)((obj)+1)))

@implementation LibraryClass

- (id) allocWithZone: (NSZone*)z
{
  return [self allocWithZone: z extra: sizeof(_LibraryClass_ext)];
}

- (int) var1
{
  return LIBRARYCLASS_EXTRA(self)->ivar1;
}

@end