Re: passing temporary storage as a non-const parameter to a function

[Lionel B]

jjleto wrote:
> Hello,
>
> When I compile the following code:
>
>       #include <iostream>
>       #include <string>
>       using namespace std;
>
>       void f1(const string& msg) { cout << msg << endl; }
>       void f2(string& msg) {  cout << msg << endl; }
>
>       int main()
>       {
>               f1(string("foo")); // OK
>               f2(string("foo")); // NOK.
>       }
>
> I've got the following error on the line calling f2():
>
> error: invalid initialization of non-const reference of type
> 'std::string&' from a temporary of type 'std::string' (gcc 3.3.4)

Correct behaviour.

> I understand that in this case, if I changed the string
> in the function, i could not use it after the function
> returns; but in some cases, I need to use it.
>
> How do I handle this ?

Use a temporary.

int main()
{
f1(string("foo")); // OK
string msg("foo");
f2(msg); // OK now (msg not temporary).
}

Alternatively:

void f2(const string& msg) {string tmp(msg); tmp+="bar"; cout << tmp
<< endl;}

Regards,

-- 
Lionel B