TaggedPointer

@property (nonatomic, copy) NSString *test;

  for (int i = 0; i < 1000; i++) {
      dispatch_async(dispatch_get_global_queue(0, 0), ^{
          self.test = [NSString stringWithFormat:@"%@",@"123"];
      });
  }

  for (int i = 0; i < 1000; i++) {
      dispatch_async(dispatch_get_global_queue(0, 0), ^{
          self.test = [NSString stringWithFormat:@"%@",@"abababababababababababababab"];
      });
  }

- (void)setTest:(NSString *)test {
    if (![_test isEqualToString:test]) {
        [_test release];
        _test = [test copy];
        [test release];
    }
}

objc_release(id obj)
{
    if (!obj) return;
    if (obj->isTaggedPointer()) return;
    return obj->release();
}

objc_object::isTaggedPointer()
{
    return _objc_isTaggedPointer(this);
}

#   define _OBJC_TAG_MASK 1UL
static inline bool 
_objc_isTaggedPointer(const void * _Nullable ptr)
{
    return ((uintptr_t)ptr & _OBJC_TAG_MASK) == _OBJC_TAG_MASK;
}