爲什麼pthread_key_create析構函數被多次調用？

我的代碼：爲什麼pthread_key_create析構函數被多次調用？

const uptr kPthreadDestructorIterations = 2; 

static pthread_key_t key; 
static bool destructor_executed; 

void destructor(void *arg) { 
    uptr iter = reinterpret_cast<uptr>(arg); 
    printf("before destructor, the pthread key is %ld\n", iter); 
    if (iter > 1) { 
     ASSERT_EQ(0, pthread_setspecific(key, reinterpret_cast<void *>(iter - 1))); 
     return; 
    } 
    destructor_executed = true; 
} 

void *thread_func(void *arg) { 
    uptr iter = reinterpret_cast<uptr>(arg); 
    printf("thread_func, the pthread key is %ld\n", iter); 
    return reinterpret_cast<void*>(pthread_setspecific(key, arg)); 
} 

static void SpawnThread(uptr iteration) { 
    destructor_executed = false; 
    pthread_t tid; 
    ASSERT_EQ(0, pthread_create(&tid, 0, &thread_func, 
       reinterpret_cast<void *>(iteration))); 
    void *retval; 
    ASSERT_EQ(0, pthread_join(tid, &retval)); 
    ASSERT_EQ(0, retval); 
} 

int main(void) { 
    ASSERT_EQ(0, pthread_key_create(&key, &destructor)); 
    SpawnThread(kPthreadDestructorIterations); 
    //EXPECT_TRUE(destructor_executed); 
    GOOGLE_CHECK(destructor_executed); 
    SpawnThread(kPthreadDestructorIterations + 1); 
    //EXPECT_FALSE(destructor_executed); 
    GOOGLE_CHECK(destructor_executed); 
    return 0; 
}

輸出：

$ ./pthread_key 2>&1 
thread_func, the pthread key is 2 
before destructor, the pthread key is 2 
before destructor, the pthread key is 1 
thread_func, the pthread key is 3 
before destructor, the pthread key is 3 
before destructor, the pthread key is 2 
before destructor, the pthread key is 1

有隻有2個線程，而是叫5倍的析構函數，爲什麼呢？

來源

2017-09-15 Victor S

'pthread_key_t'沒有析構函數。這很簡單c。 – user0042

我回滾到C++標記，因爲代碼顯然是C++。這種語言的東西應該先清除。如果這是爲了解決C問題，請提供C代碼。但看着它，我會認爲這不是一個語言問題，而是一個關於'pthread_key_t'如何工作的問題。 –

爲什麼不使用std :: threads？ – 2017-09-15 09:09:18

The documentation holds the answer：

調用從一個特定的線程的數據析例程pthread_setspecific()可能會導致無論是在丟失的存儲（在後破壞至少PTHREAD_DESTRUCTOR_ITERATIONS嘗試）或無限循環。

來源

2017-09-15 09:37:33

爲什麼pthread_key_create析構函數被多次調用？

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