c++ - How to allocate from heap with the correct memory alignment for InterlockedIncrement function? -

this code seems work, have used interlockedincrement function correctly? correct memory alignment of m_count of primary concern. assume we're on x86-64 system , compile 64-bit application (in case matters). way, actual purposes can't declare m_count volatile long , use interlockedincrement(&m_count); must pointer data in heap.

#include <windows.h> #include <malloc.h>  class threadsafecounter { public:     threadsafecounter()     {         // arguments size , alignment correct?         void* placement = _aligned_malloc( sizeof(long), sizeof(long) );         m_count = new (placement) long(0);     }     ~threadsafecounter()     {         _aligned_free( const_cast<long*>(m_count) );     }      void addone()     {         interlockedincrement(m_count);     }      long getcount()     {         return *m_count;     }  private:     volatile long* m_count; }; 

the heap allocator aligns returned addresses native platform word size. 4 bytes x86, 8 bytes x64. using long, 32-bit on either platform msvc. no need jump through _aligned_malloc() hoop.