Compiler Warning (level 1) C4291

'declaration' : no matching operator delete found; memory will not be freed if initialization throws an exception

A placement new is used for which there is no placement delete.

You could reproduce this error by defining the following class in a global namespace:

typedef unsigned int size_t;

class MemBuffer_t {
public:
   void *Alloc(size_t);
};

MemBuffer_t memBuffer;

void *operator new(size_t size, MemBuffer_t &rBuffer)
{
   return rBuffer.Alloc(size);
}

class X {
public:
   X(int);
};

void f()
{
   X *pX = new (memBuffer) X(10);
}

This warning will only occur if the user compiles the code with /GX, exception handling enabled.

The fix for the warning is to declare and/or define the following operator delete after you define your operator new:

void operator delete(void *pMem, MemBuffer_t &rBuffer);