- (id)retain
{
    NSIncrementExtraRefCount(self);
    return self;
}

inline void
NSIncrementExtraRefCount(id anObject)
{
    if(((struct obj_layout *)anObject[-1].retained == UINT_MAX - 1)
        [NSException raise: NSInternalInconsistancyException
                    format: @"NSIncrementExtraRefCount() asked to increment too far"];

    ((struct obj_layout *)anObject)[-1].retained++;
}