Re: member variable of STL string class

"Alf P. Steinbach" <>
Fri, 22 Aug 2008 11:08:26 +0200
* Alex Blekhman:

"George" wrote:

I have tried the code, no warning and output is
"", what is wrong?

string foo()
    string b;
    return b;

In the code above you do not return a reference to the local
variable `b'. Instead, you return a copy of `b'. It is OK to retun
copies of local objects from a function.

However, you have other problem:

int main()
    string& s1 = foo();

    cout << s1 << endl;

    return 0;

You bind a non-constant reference to a temporary copy of an
object. This is unsafe and conflicts with C++ Standard. Compiler
rightfully warns you with C4239 warning about this. If you don't
see this warning, then go to project settings and select warning
level 4 in C/C++ category.

And perhaps (best) add

   #pragma warning( 4: 4239 )
   #pragma warning( error: 4239 )

to source code.

Disclaimer: haven't tried it, but will do that. I just hadn't thought of it
earlier. Guess George's problem isn't that common, but, best be prepared! :-)


- Alf

A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
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