c++11 - keeping track of allocated sizes if using std::allocator -


if use std::allocator in myvector<t, std::allocator<t> > (reimplementation of std::vector) , have expanding function 

 inline void expand(std::size_t e){         // expand capacity e elements         t * p = m_allocator.allocate(e);         ...         store pointers [p, p+e] internally         ...  }

m_allocator internal instance of std::allocator<t>.

if delete instance of myvector, delete pointers [p,p+e] through allocator (pseudo loop)

for p in [p,p+e]:   m_allocator.destroy(p)  m_allocator.deallocate(p,e)

because std::allocator wants same arguments in deallocate function used in allocation function, need store number e somewhere internally. can avoided, doing like:

for p in [p,p+e]:       m_allocator.destroy(p)       m_allocator.deallocate(p,1)


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