Yes, I know C++, I didn't say that's the only way to allocate objects in C++, just that if you do write a heap allocated object that has virtual methods (a pret

Yes, I know C++, I didn't say that's the only way to allocate objects in C++, just that if you do write a heap allocated object that has virtual methods (a pretty common thing to want to do), then the metadata for that will be larger than 64 bits. Your malloc storing metadata non-adjacent to the allocation doesn't change the fact that there is some, and it has to be stored.