Pass by value

[kyrresc]

Hello,

I had a question regarding passing parameters by value into a function, and what exactly happens.

int* test(int b) {
    b++;
    return &b;    
}
//from main:

int a = 5; //a is stored somewhere in memory
cout << test(a); //in the call we basically say int b = a; i.e. b will be a copy of a stored somewhere else in memory. In the test-function we then increase the value of the b-parameter by one, so if we de-reference the address of b:
cout << *test(a); //the output is 6. 

Is the above correct re. what happens?

[Peter87]

b will no longer exist after the function has ended so the function will actually return a pointer to a variable that no longer exist. Dereferencing the returned pointer is therefore not safe and there is no guarantees what will happen if you do so.

[kyrresc]

Thanks. Is that due to the scope? I.e. b is created at a new memory location(different from a) when the function is called and then deleted when the function ends?

[Peter87]

Yes. b goes out of scope when the test function ends.