Question

Should not a compiler call the destructor of the future future right after the main finishes, that is, should not be the function f() called anyway? (gcc 4.7.2 doesn’t do that).

#include <iostream>
#include <thread>
#include <future>

using namespace std;

void f() {
    cout << "thread...\n";
}

int main() {
    auto future = async(&f);
    cout << "I am main\n";
}

edit: I get only Hello from main. The text thread... is NOT printed at all.

edit 2: Does the destructor of a future call wait()??

Answer 1

Attention: outdated information (pre-C++14) below. See Jonas’ answer for up-to-date information.

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Should not a compiler call the destructor of the future future right after the main finishes

Right before main finishes. But yes.

that is, should not be the function f() called anyway?

No, why? What makes you think that the destructor of std::future would do that? This isn’t the destructor’s job. In fact, according to §30.6.6/9, the only function of the destructor is to release the shared state of the future and destroy *this. Nothing more.