Did I make a dangling reference?

Question

Normally, I'd omit the std::vector but that would require me to make my function take a const int&. What I want to know is since there's a temporary vector if I have a dangling reference. Is it safe to modify its elements?

#include <iostream>
#include <vector>

void foo(int& i)
{
    i = 42;
}

void foo(int&& i)
{
    std::cout << "int&&";
}

int main()
{
    for (auto&& i : std::vector<int>{1, 2, 3})
    {
        foo(std::forward<decltype(i)>(i));
    }
}

1) Your code does not hav a dangling reference. 2) If you _do_ have a dangling reference then it's not ok to modify the value it references. — Captain Obvlious, Feb 26 '15 at 23:54
_"Normally, I'd omit the std::vector but that would require me to make my function take a const int&."_ Eh? — Lightness Races in Orbit, Feb 27 '15 at 00:01
@LightnessRacesinOrbit If he drops the `std::vector` part then the deduced `initializer_list` will only allow `const` access to its elements. — Praetorian, Feb 27 '15 at 00:08

score 2 · Answer 1 · answered Feb 27 '15 at 00:02

2

Your temporary vector survives for the lifetime of the loop, due to the way in which the ranged-for statement is defined. Therefore, there are no dangling references here and your program is safe. Modify away.

answered Feb 27 '15 at 00:02

Lightness Races in Orbit

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Did I make a dangling reference?

1 Answers1