FIX: Calling delete or free() in ATL Causes Access Violation

void __cdecl free(void* p)
{
#ifndef _ATL_NO_MP_HEAP
   if (_Module.m_phHeaps == NULL)
#endif
      HeapFree(_Module.m_hHeap, 0, p);
#ifndef _ATL_NO_MP_HEAP
   else
   {
      HANDLE* pHeap = ((HANDLE*)p)-nOffsetBlock;
      HeapFree(*pHeap, 0, pHeap);
   }
#endif
}
				

RESOLUTION

The implementation of free() needs to be modified in Atlimpl.cpp. One option to resolve this problem is to just return if the pointer is NULL:

   void __cdecl free(void* p)
   {
      if (p == NULL)  // Add this line.
         return;      // Add this line.
   #ifndef _ATL_NO_MP_HEAP
      if (_Module.m_phHeaps == NULL)
   #endif
         HeapFree(_Module.m_hHeap, 0, p);
   #ifndef _ATL_NO_MP_HEAP
      else
      {
         HANDLE* pHeap = ((HANDLE*)p)-nOffsetBlock;
         HeapFree(*pHeap, 0, pHeap);
      }
   #endif
   }
				

Another option to resolve this problem is to #define _ATL_NO_MP_HEAP. This prevents the problematic code from being included. However, this does turn off the optimization that ATL adds for multi-processor machines. You have only one heap regardless of the number of processors. Heap access may be less than optimal because access from multiple threads is serialized.