多线程编程：pthread_key_t AND __thread

pthread_key_t

struct TlsInfo { // thread local storage Information
    ~TlsInfo() {
        printf("%d TlsInfo destructor done\n", tid);
    }
    TlsInfo(unsigned int t) : tid(t) {}
    unsigned int tid;
    /*other information*/
};

#define gettid() syscall(SYS_gettid)

pthread_key_t pkey;
pthread_once_t ponce;

void pthread_key_destructor(void* arg) {
    struct TlsInfo* ptr = (struct TlsInfo*) arg;
    delete ptr;
    printf("pthread_key_destructor done\n");
}

void pthread_key_create_wrapper() {
    pthread_key_create(&pkey, pthread_key_destructor);
}

void* fun(void* arg) { // run several fun simultaneously
    pthread_once(&ponce, pthread_key_init_wrapper);
    struct TlsInfo* ptr = new TlsInfo(gettid());
    pthread_setspecific(pkey, ptr);

    /*loop : doing something*/

    return NULL;    
}

__thread

__thread struct TlsInfo* ptr = NULL;

void* fun(void* arg) { // run several fun simultaneously
    printf("ptr supposed to be NULL : ptr = %lld\n", (long long)ptr);
    ptr = new TlsInfo(gettid());
    cout << ptr->tid << endl;
    return NULL;    
}