Returning a std::vector by reference caused segmentation fault

Question

I have a function which creates a very large std::vector. When returning this vector, I do not want to copy it again, due to its size. Therefore, I want to return a reference to that vector. However, doing so gives me a segmentation fault. Why is this? What is the solution?

Here is my code:

std::vector<int>& Foo()
{
    std::vector<int> x(100000, 50);
    return x;
}

int main()
{
    std::vector<int> y = Foo();
    return 0;
}

@melak47: The answer section is down here: ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ — Lightness Races in Orbit, Aug 21 '15 at 17:30
You can probably return without the reference. Odds are good the compiler is smart. — user4581301, Aug 21 '15 at 17:32
See [here](http://stackoverflow.com/questions/22655059/why-it-is-ok-to-return-vector-from-function/22655120#22655120) also please. — πάντα ῥεῖ, Aug 21 '15 at 17:33

score 6 · Answer 1 · answered Aug 21 '15 at 17:31

Your vector is a local variable. It exists within the function and is destroyed when the function ends.

Consequently, your reference is dangling. It refers to an object that no longer exists.

Just return by value; your compiler is smart enough to optimise away a pointless copy, even if you are pre-C++11 and thus don't have move semantics.

Returning a std::vector by reference caused segmentation fault

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