int g_tickets = 100;
pthread_mutex_t g_mutex = PTHREAD_MUTEX_INITIALIZER;
void* thread_fun1(void * arg)
{
    while(true)
    {
        pthread_mutex_lock(&g_mutex);
        if(g_tickets>0)
        {
            cout<<"thread 1 sell tickets:"<<g_tickets--<<endl;
        }
        else
        {
            //pthread_mutex_unlock(&g_mutex); 
            pthread_mutex_lock(&g_mutex);//误将pthread_mutex_unlock写成pthread_mutex_lock
            break;
        }
        //pthread_mutex_unlock(&g_mutex);
        pthread_mutex_lock(&g_mutex);//误将pthread_mutex_unlock写成pthread_mutex_lock
    }
    return (void*)1;
}
void* thread_fun2(void * arg)
{
    while(true)
    {
        pthread_mutex_lock(&g_mutex);
        if(g_tickets>0)
        {
            cout<<"thread 2 sell tickets:"<<g_tickets--<<endl;
        }
        else
        {
            pthread_mutex_unlock(&g_mutex);
            break;
        }
        pthread_mutex_unlock(&g_mutex);
    }
    return (void*)2;
}
int main()
{
    pthread_t tid1,tid2;
    void *ret1 = nullptr;
    void *ret2 = nullptr;

    pthread_create(&tid1,nullptr,thread_fun1,nullptr);
    pthread_create(&tid2,nullptr,thread_fun2,nullptr);

    pthread_join(tid1,&ret1);
    pthread_join(tid2,&ret2);

    cout<<"ret1:"<<ret1<<endl;
    cout<<"ret2:"<<ret2<<endl;
    return 0;
}

cc =g++ -g -std=c++2a -fmodules-ts
prom = main
deps = $(shell find ./ -name "*.h")
src = $(shell find ./ -name "*.cpp")
obj = $(src:%.cpp=%.o)
lib = -lboost_thread       -lboost_system       -pthread

$(prom):$(obj)
    $(cc) -o $(prom) $(obj) $(lib)
%.o:%.cpp $(deps)
    $(cc) -c $< -o $@ $(lib)

make
./main

ps aux | grep main

sudo gdb main 23848