C6334

The new home for Visual Studio documentation is Visual Studio 2017 Documentation on docs.microsoft.com.

The latest version of this topic can be found at C6334.

warning C6334: sizeof operator applied to an expression with an operator may yield unexpected results

This warning indicates a misuse of the sizeof operator. The sizeof operator, when applied to an expression, yields the size of the type of the resulting expression.

For example, in the following code:

char     a[10];  
size_t   x;  
  
x = sizeof (a - 1);  

x will be assigned the value 4, not 9, because the resulting expression is no longer a pointer to the array a, but simply a pointer.

The following code generates this warning:

void f( )  
{     
  size_t x;  
  char a[10];  
  
  x= sizeof (a - 4);  
  // code...  
}  

To correct this warning, use the following code:

void f( )     
{  
  size_t x;  
  char a[10];  
  
  x= sizeof (a) - 4;  
  // code...  
}   

sizeof Operator