我根本找不到的C內存泄漏

Question

因此，該程序一切正常，但我遇到了非常煩人的內存泄漏。 我在電腦前坐了幾個小時，可以弄清楚。

我們有兩個很簡單的實現方式，一個結構是一個雙鏈表，一個是存儲該雙鏈表的哈希表。

現在，我將關鍵字和數據插入到雙向鏈接列表中，這里是函數。

void htable_insert(htable* ht, int key, int data) {
    // TODO: Insert a new entry with the given key and data
    // Overwrite the old data if the key already exists, duplicate keys are not allowed
    ht_entry *new_node;
    ht_entry *head;
    ht_entry *it;
    int sameKey;
    int bucketPosition;

    new_node = (ht_entry*)malloc(1*sizeof(ht_entry));
    bucketPosition = key % ht->size;
    sameKey = 0;

    for(it = ht->entries[bucketPosition]; it != NULL; it = it->next)
    {
      if(it->key == key) {
        it->data = data;
        sameKey = 1;
        free(new_node);
        new_node = NULL;
        break;

      }
    }

    if(!sameKey && new_node) {
      head = ht->entries[bucketPosition];
      if (head == NULL) {
        new_node->key = key;
        new_node->data = data;
        new_node->next = head;
        new_node->prev = NULL;
        ht->entries[bucketPosition] = new_node;
        new_node = NULL;

      } else {
        new_node->key = key;
        new_node->data = data;
        new_node->next = head;
        // new_node->prev = head;
        head->prev = new_node;
        head = new_node;
        ht->entries[bucketPosition] = head;

      }
    }
    // free(new_node);
    new_node = NULL;
    printf("%s\n %d", "INSERT:", key);
    for(it = ht->entries[bucketPosition]; it != NULL; it = it->next){
      printf("it->key: %d\nit->data: %d\n", it->key, it->data);
    }


    printf("%s\n", "-------------------------------");


}

這是我的valgrind消息：

==10692== Memcheck, a memory error detector
==10692== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==10692== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==10692== Command: ./chain_hash_table.out
==10692== 
==10692== 
==10692== HEAP SUMMARY:
==10692==     in use at exit: 72 bytes in 3 blocks
==10692==   total heap usage: 10 allocs, 7 frees, 376 bytes allocated
==10692== 
==10692== 24 bytes in 1 blocks are definitely lost in loss record 2 of 3
==10692==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10692==    by 0x4007EE: htable_insert (htable.c:53)
==10692==    by 0x400BD2: main (main.c:14)
==10692== 
==10692== 48 (24 direct, 24 indirect) bytes in 1 blocks are definitely lost in loss record 3 of 3
==10692==    at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10692==    by 0x4007EE: htable_insert (htable.c:53)
==10692==    by 0x400C25: main (main.c:18)
==10692== 
==10692== LEAK SUMMARY:
==10692==    definitely lost: 48 bytes in 2 blocks
==10692==    indirectly lost: 24 bytes in 1 blocks
==10692==      possibly lost: 0 bytes in 0 blocks
==10692==    still reachable: 0 bytes in 0 blocks
==10692==         suppressed: 0 bytes in 0 blocks
==10692== 
==10692== For counts of detected and suppressed errors, rerun with: -v
==10692== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)

我所知道的始終是第一次插入表，這就是為什么它在第一次插入后在main（18）行上顯示其余內容的原因。

謝謝你們的時間和幫助:)

Answer 1

檢查循環中的break語句，它在第一次迭代時中斷，並且不取消分配節點。

中斷應放在for循環內。

Answer 2

如果要在C程序中分配空間，除非最后釋放所有內容，否則最終將導致內存泄漏。

對於您當前的程序，我假設您最終無法正確釋放。 因此，問題不在htable_insert函數之內，而在您的釋放/清除函數之內。

如果您在htable_insert釋放鏈表節點，那么您將無法在程序的其余部分中訪問它們，並且會遇到段錯誤。