Why cast unused return values to void?

Question

int fn();

void whatever()
{
    (void) fn();
}

Is there any reason for casting an unused return value to void, or am I right in thinking it\'s a c

Answer 1

Casting to void is used to suppress compiler warnings for unused variables and unsaved return values or expressions.

The Standard(2003) says in §5.2.9/4 says,

Any expression can be explicitly converted to type “cv void.” The expression value is discarded.

So you can write :

//suppressing unused variable warnings
static_cast(unusedVar);
static_cast(unusedVar);
static_cast(unusedVar);

//suppressing return value warnings
static_cast(fn());
static_cast(fn());
static_cast(fn());

//suppressing unsaved expressions
static_cast(a + b * 10);
static_cast( x &&y || z);
static_cast( m | n + fn());

All forms are valid. I usually make it shorter as:

//suppressing  expressions
(void)(unusedVar);
(void)(fn());
(void)(x &&y || z);

Its also okay.