如何檢查 C 中的 memory 泄漏？

Question

這是我第一次使用動態 memory 分配，我不知道如何在我的代碼中檢查 memory 泄漏

總的來說，我如何在 Visual Studio 中檢查 memory 泄漏？ 我不知道如何跟蹤堆和堆棧，所以我主要是在黑暗中拍攝。

我應該提到我使用了 windows 10 並且據我所知 Valgrind 不提供對 W10 的支持

Dictionary* createDic(Dictionary* dics, int* size) {
    Dictionary* temp = NULL;
    //some extra code for the variables below which arent al that important for the question
    temp = malloc(++*size * sizeof(Dictionary));
    if (temp==NULL)
    {
        printf("\nThe creation of the dictionary has failed!");
        *size+=-1;
        freeArray(splitReciever,count);
        return dics;
    }
    for (int i = 0; i < (*size - 1); i++)
    {
        temp[i] = dics[i];
    }
    temp[*size - 1].languages = splitReciever;
    temp[*size - 1].numOfLanguages = count;
    temp[*size - 1].wordList = NULL;
    dics = temp;
    return dics;
}

我還想知道這段代碼是否會再次起作用，而不會導致 memory 泄漏？

Dictionary* createDic(Dictionary* dics, int* size) {
    Dictionary* temp = NULL;
    //some extra code for the variables below which arent al that important for the question
    temp = realloc(dics , ++*size * sizeof(Dictionary));
    if (temp==NULL)
    {
        printf("\nThe creation of the dictionary has failed!");
        *size+=-1;
        freeArray(splitReciever,count);
        return dics;
    }
    temp[*size - 1].languages = splitReciever;
    temp[*size - 1].numOfLanguages = count;
    temp[*size - 1].wordList = NULL;
    dics = temp;
    return dics;
}

Answer 1

To check for memory leaks tools like valgrind can be used – while these cannot give you guarantees of (in-)existence of memory leaks or for finding any location of a memory leak – there are false positives and negatives possible – their results still provide pretty關於你應該在哪里再次檢查你的代碼的有價值的提示。

監控 memory 的消耗也可以給你進一步的提示； 如果它超出合理限制，那么您可能有 memory 泄漏。

對於您的具體示例：

第一個變體可能會產生 memory 泄漏，但不一定：

Dictionary d1 = ...;
Dictionary d2 = createDic(d1, &n);

// now you could use both of d1 and d2
// however risk of double deletion if re-allocation failed;
// need to compare d1 and d2 for equality before freeing them

Dictionary d3 = ...;    // assume this is the sole pointer to d3
d3 = createDic(d3, &n); // if re-allocation succeeded last reference to
                        // old dictionary is lost -> memory leak

第二種變體避免了這種情況，但有另一個缺點：

Dictionary d1 = ...;
Dictionary d2 = createDic(d1, &n);

如果成功，指針d1會失效，讀取它會導致未定義的行為。 因此，您還必須將其更新為新值。

總之，第二個變體應該會帶來更少的麻煩，所以我更喜歡它。 順便說一句：如果您修改該變體以在成功返回之前刪除舊字典，則相當於第一個變體......