CODEWITHSUNDEEP
c++referencescope
Brian R. Bondy
Brian R. Bondy

Reputation: 347416

In C++, is it safe to extend scope via a reference?

In C++, is it safe to extend scope via a reference?

In code, what I mean is: 

MyCLass& function badIdea()
{
    MyClass obj1;
    ...
    return obj1;
}

Upvotes: 10

Views: 5217

Answers (3)

Harald Scheirich
Harald Scheirich

Reputation: 9764

It is NOT safe to extend the scope via reference. Objects in C++ are not reference counted when obj1 goes out of scope it will be deleted, refering to the result of badIdea() will only get you into trouble

Upvotes: 22

Motti
Motti

Reputation: 114765

The only place it's OK to extend a scope with a reference is with a const reference in namespace or function scope (not with class members).

const int & cir = 1+1; // OK to use cir = 2 after this line

This trick is used in Andrei Alexandrescu's very cool scope guard in order to capture a const reference to a base class of the concrete scope guard.

Upvotes: 16

peterchen
peterchen

Reputation: 41106

Please clarify what you do mean.

Assuming you intend to do this:

int * p = NULL;
{
  int y = 22;
  p = &y;
}
*p = 77; // BOOM!

Then no, absolutely not, scope does not get extended by having a reference.

You may want to look at smart pointers, e.g. from boost libraries: clickety

Upvotes: 1

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