Is NRVO valid with exception throwing in body?

Question

I am looking to understand the limitations of NRVO in C++. Would a function with an initial named declaration and a single return be optimised for NRVO and elide T val, even though the function myFunc() has a throwing potential?

T myFunc(bool toThrow) {
    T val;

    if (toThrow) {
        throw std::exception();
    }

    // Do other things here.

    return val;
}

Did you try it? Did the compiler use NRVO? If it did, then it probably can. — eerorika, Jul 20 '19 at 04:49
@Zereges I would have thought the same thing but I couldn't find make Clang *not* use NRVO, even for a type with side-effects in both constructor and destructor. — Jørgen Fogh, Jul 21 '19 at 11:42

score 1 · Accepted Answer · answered Jul 21 '19 at 11:36

1

I tested a few versions of your code on C++ Insights and Compiler Explorer.

The short answer is yes, the compiler will most likely use NRVO.

answered Jul 21 '19 at 11:36

Jørgen Fogh

7,516
2
36
46

Is NRVO valid with exception throwing in body?

1 Answers1