Re: std::ostringstream misunderstanding

Hi,

Consider the following code:

#include <sstream>
#include <iostream>
int main()
{
    std::string lcStr = static_cast<std::ostringstream&>(
       std::ostringstream() << "abc" << "def").str();

    std::cout << lcStr << std::endl;

}

It produces this:

0x2f10def

Using gcc version 4.0.1 on Mac Os X and gcc 3.3.3 on Linux Fedora Core
2.

My question is why does does it produce this? I would have thought the
code above would be very similar to the following:

#include <sstream>
#include <iostream>

int main()
{
    std::ostringstream lcStream;

    std::string lcStr = static_cast<std::ostringstream&>(
       lcStream << "abc" << "def").str();

    std::cout << lcStr << std::endl;
}

which produces the output I was hoping for:

abcdef

Obviously the main difference is the creation and usage of a temporary
in the former case and the usage of a local in the latter case. The
temporary object should not be destructed until the ';' is reached so
I'm pretty sure the object is not getting destructed early or anything
like that.

I'm very hesitant to call this a compiler problem, I'm guessing it is
more likely that I'm not using the objects correctly.The std::string
that the std::ostringstream contains as a member has the address
stored as it contents. The question I have is why?

- pete