CODEWITHSUNDEEP
c++reference
user13645
user13645

Reputation: 23

Compiler warning when returning a reference to a local object

How should i return a reference to object without getting a warning for example:

std::string& GetString()
{
    std::string str = "Abcdefghijklmnopqrstuvwxyz";
    return str;
}

int main()
{
    std::string str = GetString();
}

This results a warning on compliation.

Upvotes: 2

Views: 243

Answers (2)

tsiki
tsiki

Reputation: 1799

Technically you could create it to the heap and return a reference (edit: memory leaking example, don't try this at home (thanks James)):

string& GetString() {
    string * strPtr;
    strPtr = new string("qweqweqwe");
    string &str2 = (*strPtr);
    return str2;
}

int main() {
    string str = GetString();
    return 0;
}

But technicalities aside, passing by value is the better option here (as said above).

Upvotes: 0

James McNellis
James McNellis

Reputation: 355049

In your example, you are returning a reference to the local variable str. As soon as GetString() returns, str is destroyed and the reference is invalid (it refers to an object that has been destroyed).

If you return a reference to an object, it must be an object that will still be valid after the function returns (e.g., it can't be a local variable).

In this particular case, you have to return str by value. The most common use for returning a reference is for member functions that return a reference to a member variable.

Upvotes: 14

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