return a local std::string

[Jun Yan]

Hi all,

I am seeing this kind of code,

std::strnig foo()
{
std::string ret = "bla bla";
return ret;
}

Just curious, what will happen, when call foo?

thanks,


Jun

 

[Gert-Jan de Vos]

Hi all,

I am seeing this kind of code,

std::strnig foo()
{
    std::string ret = "bla bla";
    return ret;
}

Just curious, what will happen, when call foo?

It should not compile since there is no "strnig" in the std
namespace..

Seriously: The caller of foo() gets a copy of the local string ret,
same contents. This is fine as you are returning the string object by
value. If you would try to return it by reference, then you would get
problems. A reference to a local object of a function is no longer
valid after the function returns. A copy of its value is. Clear?

 

[peter koch]

Hi all,

I am seeing this kind of code,

std::strnig foo()
{
    std::string ret = "bla bla";
    return ret;

}

Just curious, what will happen, when call foo?

It will return a string for you to use; whether the string is copied
or not is implementation-defined. In your example, I am quite
confident that no copy will take place, provided you ask the compiler
to optimize just a little.

/Peter