Question

我在C中有一个纸牌游戏（我必须在C，类项目中制作）。我创建了一种方法，用于将Structs从一个动态数组移动到另一个动态数组。不幸的是，该方法最初工作，但后来当我在程序中调用它时，它开始抛出malloc（）错误。 Deck是包含int size和动态分配Card *deck的结构，Card是用于保存单张卡的结构。有什么我缺少的，或者必须以另一种方式定义？

void moveCard(Deck *src, Deck *dest, int n){
    Card *tmpCards = NULL;
    Card tmp = (*src).deck[n];                          // get card to be copied
    int newSize = dest->size + 1;                       //increase dest size by 1
    tmpCards = (Card *) malloc(sizeof(Card) * newSize); // allocate new memory area
    memmove(&(tmpCards[0]), &(dest->deck[0]), sizeof(Card) * (newSize - 1)); 
        // copy all the cards from old memory area to new area
    dest->deck = tmpCards;  // reassign old pointer to new memory area
    dest->size = newSize;   // reevaluate size
    dest->deck[newSize - 1] = tmp; // copy card to end of new area


    tmpCards = NULL; // empty out pointer (no functionality, just for easier reading)
    newSize = src->size; // reevaluate newSize 
    tmpCards = (Card *) malloc(sizeof(Card) * (newSize - 1));
                     // allocate smaller mem area by 1
    memmove(&(tmpCards[0]),&(src->deck[0]), sizeof(Card) * (n));
                     // copy all cards up to the n-th point 
    memmove(&(tmpCards[n]),&(src->deck[n+1]), sizeof(Card) * (newSize - n));
                     // copy all cards from the n+1 -th point

    src->size = newSize -1; // reevaluate size
    src->deck = tmpCards;     // reassign pointer

    // since all input parameters were pointers, no return is necessary
}

编辑：，因为我不会释放记忆这一事实。原始代码中包含2个免费命令（free(dest->deck)和free(src->deck)）。但只有其中一个有效。另一个因为一些奇怪的原因再次创建了内存损坏，所以我发现它更好，而不是把它们放到这个例子中。

Answer 1

我认为你的内存耗尽，因为你没有释放任何内存。你只是在分配新的内存。

void moveCard(Deck *src, Deck *dest, int n){
    Card *tmpCards = NULL;
    Card tmp = (*src).deck[n];                          // get card to be copied
    int newSize = dest->size + 1;                       //increase dest size by 1
    tmpCards = (Card *) malloc(sizeof(Card) * newSize); // allocate new memory area
    memmove(&(tmpCards[0]), &(dest->deck[0]), sizeof(Card) * (newSize - 1)); 
        // copy all the cards from old memory area to new area

    // **** CORRECTION ****
    // Free previously allocated memory for dest->deck
    free(dest->deck);

    dest->deck = tmpCards;  // reassign old pointer to new memory area
    dest->size = newSize;   // reevaluate size
    dest->deck[newSize - 1] = tmp; // copy card to end of new area


    tmpCards = NULL; // empty out pointer (no functionality, just for easier reading)
    newSize = src->size; // reevaluate newSize 
    tmpCards = (Card *) malloc(sizeof(Card) * (newSize - 1));
                     // allocate smaller mem area by 1
    memmove(&(tmpCards[0]),&(src->deck[0]), sizeof(Card) * (n));
                     // copy all cards up to the n-th point 
    memmove(&(tmpCards[n]),&(src->deck[n+1]), sizeof(Card) * (newSize - n));
                     // copy all cards from the n+1 -th point

    src->size = newSize -1; // reevaluate size

    // **** CORRECTION ****
    // Free previously allocated memory for src->deck
    free(src->deck);

    src->deck = tmpCards;     // reassign pointer

    // since all input parameters were pointers, no return is necessary
}

PS 您应该使用memcpy代替memmove。如果源和目标重叠，memmove是正确的函数。如果源和目标不重叠，memcpy是正确的函数。

用于在动态数组之间移动结构的C方法

1 个答案: