C++0x has no semaphores? How to synchronize threads?

Question

Is it true that C++0x will come without semaphores? There are already some questions on Stack Overflow regarding the use of semaphores. I use them (posix semaphores) all the

Answer 1

You can easily build one from a mutex and a condition variable:

#include 
#include 

class semaphore
{
private:
    std::mutex mutex_;
    std::condition_variable condition_;
    unsigned long count_ = 0; // Initialized as locked.

public:
    void notify() {
        std::lock_guard lock(mutex_);
        ++count_;
        condition_.notify_one();
    }

    void wait() {
        std::unique_lock lock(mutex_);
        while(!count_) // Handle spurious wake-ups.
            condition_.wait(lock);
        --count_;
    }

    bool try_wait() {
        std::lock_guard lock(mutex_);
        if(count_) {
            --count_;
            return true;
        }
        return false;
    }
};