Checking for overflow of integer addition needs to be done with care, because automatic type promotion can prevent the check from working as intended, with the same value (true or false) always being returned.

Use an explicit cast to make sure that the result of the addition is not implicitly converted to a larger type.

On a typical architecture where short is 16 bits and int is 32 bits, the operands of the addition are automatically promoted to int, so it cannot overflow and the result of the comparison is always false.

The code below implements the check correctly, by using an explicit cast to make sure that the result of the addition is unsigned short (which may overflow, in which case the comparison would evaluate to true).

Preserving Rules

Understand integer conversion rules