multithreading - C++: Simple return value from std::thread?

Question

With win32 threads I have the straight forward GetExitCodeThread() that gives me the value which the thread function returned. I'm looking for something similar for std::thread (or boost threads)
As I understand this can be done with futures but how exactly?

Answer 1

See this video tutorial on C++11 futures.

Explicitly with threads and futures:

#include <thread>
#include <future>

void func(std::promise<int> && p) {
    p.set_value(1);
}

std::promise<int> p;
auto f = p.get_future();
std::thread t(&func, std::move(p));
t.join();
int i = f.get();

Or with std::async (higher-level wrapper for threads and futures):

#include <thread>
#include <future>
int func() { return 1; }
std::future<int> ret = std::async(&func);
int i = ret.get();

I can't comment whether it works on all platforms (it seems to work on Linux, but doesn't build for me on Mac OSX with GCC 4.6.1).