Usage of std::mutex

main.cpp

#include <thread>
#include <memory>
#include <mutex>
#include <iostream>
#include <vector>

#define USE_MUTEX 1

class Foo
{
public:
    Foo(){};
    double read(){
        m_mutex.lock();
        std::cout << "read" << m_foo << std::endl;
        auto val = m_foo;
        m_mutex.unlock();
        return val;
    };
    void write(double meh) {
        m_mutex.lock();
        std::cout << "write" << m_foo << std::endl;
        m_foo = meh;
        m_mutex.unlock();
    };
    
    double readNoMutex()
    {
        std::cout << "read" << m_foo << std::endl;
        return m_foo;
    }
    void writeNoMutex(double meh)
    {
        std::cout << "write" << m_foo << std::endl;
        m_foo = meh;
    }
private:
    double m_foo {0.0};
    std::mutex m_mutex;
};


int main() {

    auto foo = new Foo();
    std::vector<std::thread*> all_threads;
    for(int i = 0; i < 10; i++) {
        
        all_threads.push_back(new std::thread([=]{
#if USE_MUTEX
            foo->write(12.12 + i);
            foo->read();
#else
            foo->writeNoMutex(12.12 + i);
            foo->readNoMutex();
#endif
        }));
        
    }
    
    for(size_t i = 0, len = all_threads.size(); i < len; i++) {
        all_threads.at(i)->join();
        delete all_threads.at(i);
    }
    delete foo;
    return 0;
}