How compiler manage return inline function?

Question

Let say I have an inlined function like this:

inline double CalculateValue() {
    // some condition
    if (true) {
        // some other condition
        if (true) {
            // another condition
            if (true) {
                return 1.0;
            }

            // somethings
            std::cout << "inside1" << std::endl;
        }

        // somethings
        std::cout << "inside2" << std::endl;
    }

    return 2.0;
}

void Process() {
    double value = CalculateValue();

    value *= 100.0;

    std::cout << value << std::endl;
}

int main ()
{
    Process();
}

It will "copy and paste" the CalculateValue() function within the Process() one. The result is 100, as expected.

But if I try to emulate how this "copy and paste" will be performed, there's something I don't understand:

void Process() {
    double value;

    // some condition
    if (true) {
        // some other condition
        if (true) {
            // another condition
            if (true) {
                value = 1.0;
                return;
            }

            // somethings
            std::cout << "inside1" << std::endl;
        }

        // somethings
        std::cout << "inside2" << std::endl;
    }

    value = 2.0; 

    value *= 100.0;

    std::cout << value << std::endl;
}

int main ()
{
    Process();
}

Of course when it reaches the return statement, the rest of the function must be ignored (i.e. inside1 and inside2 must never be printed), because of the return. But if I return from the parent function (Process()), it returns immediately, so I can't ever see 100.

This means it does it another way.

How does the compiler manage this situation? I tried to create a code block, but still the return returns to the main function...

Answer 1

While writing your "emulation" you forgot to handle one of the returns. In an inlined function the compiler would kind of replace it with a goto statement.

void Process() {
    double value;

    // begin of inlined function

    // some condition
    if (true) {
        // some other condition
        if (true) {
            // another condition
            if (true) {
                value = 1.0;
                goto next;     // <<<<<<<<<<<<<<<<<<<  return replaced by goto
            }

            // somethings
            std::cout << "inside1" << std::endl;
        }

        // somethings
        std::cout << "inside2" << std::endl;
    }

    value = 2.0; 
 next:   
    //end of inlined function

    value *= 100.0;

    std::cout << value << std::endl;
}