Warning C6221

Implicit cast between semantically different integer types: comparing HRESULT to an integer. Consider using SUCCEEDED or FAILED macros instead

This warning indicates that an HRESULT is being compared to an integer other than zero.

Remarks

A success in an HRESULT (S_OK) is represented by a 0. Therefore, an implicit cast of an HRESULT to an integer generates an incorrect value and is likely to lead to the wrong result. The error is often caused by mistakenly expecting a function to return an integer when it actually returns an HRESULT.

Code analysis name: COMPARING_HRESULT_TO_INT

Example

The following code generates warning C6221 by comparing an HRESULT against an integer value:

#include <windows.h>

HRESULT f( )
{
  HRESULT hr;
  LPMALLOC pMalloc;

  hr = CoGetMalloc(1, &pMalloc);
  if (hr == 4)
  {
    // failure code ...
    return S_FALSE;
  }
  else
  {
    // success code ...
    return S_OK;
  }
}

To correct this warning, the following code uses the FAILED macro:

#include <windows.h>

HRESULT f( )
{
  HRESULT hr;
  LPMALLOC pMalloc;

  hr = CoGetMalloc(1, &pMalloc);
  if (FAILED(hr))
  {
    // failure code ...
    return S_FALSE;
  }
  else
  {
    // success code ...
    return S_OK;
  }
}

For this warning, the SCODE type is equivalent to HRESULT.

For more information, see SUCCEEDED Macro and FAILED Macro.

The use of malloc and free (and related dynamic memory allocation APIs) has many pitfalls in terms of memory leaks and exceptions. To avoid these kinds of potential leaks altogether, use the mechanisms that are provided by the C++ Standard Library (STL). These include shared_ptr, unique_ptr, and containers such as vector. For more information, see Smart pointers and C++ Standard Library.