c6396.md

description	title	ms.date	f1_keywords	helpviewer_keywords
Learn more about: Warning C6396: sizeof('integerConstant') always returns the size of the underlying integer type	Warning C6396	02/05/2024	C6396 SIZEOF_CONSTANT	C6396

Warning C6396

sizeof('integerConstant') always returns the size of the underlying integer type

Remarks

This warning indicates where an integral constant is used as a sizeof argument. Such expression always returns the size of the type of the constant. It's better to write sizeof(type) instead. This warning catches common typos in buffer offset calculations.

This check ignores character literals because buffer_size += sizeof(UNICODE_NULL) is a common idiom.

Example

void f()
{  
    int a = sizeof(5);         // C6396 reported here
}

To fix this issue, replace the integral constant with its type:

void f()
{  
    int a = sizeof(int);         // no C6396 reported here
}