class method not returning value - c++

Question

I have a method inside a class that is not returning a value.
These are the relevant variables that are being used in the method, they are in the private part of the class
int hieght_of_plane = 0 ;
int position_of_plane = 0 ;
bool landing_gear = true ;
bool is_flying = false ;
bool is_alive = true ;
And here is the method that is not returning true or false, it is in the public section of the class.
bool check_for_alive()
{
if (is_flying == false)
{
return true ;
}
if (is_flying == true)
{
if (hieght_of_plane <= 3)
{
if (landing_gear == false)
{
is_alive = false ;
return false ;
}
else if (landing_gear == true)
{
return true ;
}
}
}
}
The method seems to not do anything and then I get the no return value error
warning: control reaches end of non-void function [-Wreturn-type]
I assume that it should return false in this instance because is_flying = false so the method should return false, but it isn't.

Answer 1

The case that falls through is when flying == true and hieght_of_plane is greater than 3.
if (is_flying == true)
{
if (hieght_of_plane <= 3)
{
The 2nd if statement does not have an else, which is necessary for returning a value.
Edit 1: An else clause
The else clause should be used for the "not" case of the if statement.
For example:
if (is_flying == false)
{
return true;
}
else // This means is_flying == true
{
if (hieght_of_plane <= 3)
{
if (landing_gear == false)
{
is_alive = false ;
return false ;
}
else // implies landing_gear == true
{
return true ;
}
else // implies hieght > 3
{
return ????
}
}
You could also reduce this down to one Boolean expression.
Edit 2: Simplification
There are two functionalities here: Return true/false for a combination of conditions and to set is_alive based on a condition.
Let's say that one condition is true, all others is false.
bool check_for_alive()
{
if (is_flying && (height_of_plane <= 3) && (landing_gear == false))
{
is_alive = false;
}
return is_flying && (height_of_plane <= 3) && (landing_gear == true);
}
Note: The above does not consider the case of `(height_of_plane > 3), since this is not specified in the OP's original code.

Answer 2

the control flow would reach the end of the function when is_flying is true and hieght_of_plane is > 3. you MUST return something there.
and one more thing is the you don't always need to check that if (something == true) instead if (something) would enough, I've pointed some more below the code.
bool check_for_alive() {
if (!is_flying)
return true;
// if you reached here is_flying is true no need to check
if (hieght_of_plane <= 3) {
if (!landing_gear) {
is_alive = false;
return false;
} else {
// if you're here landing_gear is false no need to check
return true;
}
}
// what to return if we reach here? yes the control flow could reach
// here when is_flying is true and hieght_of_plane is > 3
// you must return something here.
}