C6384

warning C6384: dividing sizeof a pointer by another value

This warning indicates that a size calculation might be incorrect. To calculate the number of elements in an array, one sometimes divides the size of the array by the size of the first element; however, when the array is actually a pointer, the result is typically different than intended.

If the pointer is a function parameter and the size of the buffer was not passed, it is not possible to calculate the maximum buffer available. When the pointer is allocated locally, the size used in the allocation should be used.

Example

The following code generates this warning:

#include <windows.h>  
#include <TCHAR.h>  
  
#define SIZE 15  
  
void f( )  
{  
  LPTSTR dest = new TCHAR[SIZE];  
  char src [SIZE] = "Hello, World!!";  
  if (dest)  
  {  
    _tcsncpy(dest, src, sizeof dest  / sizeof dest[0]);   
  }  
}  

To correct this warning, pass the buffer size as shown in the following code:

#include <windows.h>  
#include <TCHAR.h>  
  
#define SIZE 15  
  
void f( )  
{  
  LPTSTR dest = new TCHAR[SIZE];  
  char src [SIZE] = "Hello, World!!";  
  if (dest)  
  {  
    _tcsncpy(dest, src, SIZE);  
  }  
}  

To correct this warning using the safe string function _tcsncpy_s, use the following code:

void f( )  
{  
  LPTSTR dest = new TCHAR[SIZE];  
  char src [SIZE] = "Hello, World!!";  
  if (dest)  
  {  
   _tcsncpy_s(dest, SIZE, src, SIZE);  
  }  
}   

Note that the use of new and delete have many pitfalls in terms of memory leaks and exceptions. To avoid these kinds of leaks and exception problems altogether, use the mechanisms that are provided by the C++ Standard Template Library (STL). These include shared_ptr, unique_ptr, and vector. For more information, see Smart Pointers and C++ Standard Library.

See Also

_mbsnbcpy_s, _mbsnbcpy_s_l
sizeof Operator