c++ - Visual Studio 抛出异常 : write acces violation. q_deck->p_deck 为 0x110112。 C语言

Question

我遇到了奇怪的错误，并且不知道该怎么办。我试图找到解决方案，但找不到适合我的解决方案。这是纸牌游戏，当我尝试将纸牌添加到我的列表(即一副纸牌)时，会显示错误。这是我的完整代码，以充分理解我的想法。它是用 c 编写的，但我使用的是 c++ 中的 cin/cout，这就是为什么我有“使用命名空间 std;”谢谢您的帮助:)

#define SIZE 52
#define HALF_SIZE 26

using namespace std;

typedef enum Suit { Diamonds, Hearts, Spades, Clubs } Suit_t;
typedef enum Power { Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten, Jack, Queen, King, Ace } Power_t;

typedef struct card {
    Suit_t suit;
    Power_t power;
}cards;

typedef struct deck {
    cards* p_deck;
    int size;
}decks;

void Deck_Creator(cards* deck) {
    for (int i = 0; i < SIZE; i++) {
        deck[i].suit = (Suit)(i / 13);
        deck[i].power = (Power)(i % 13);
    }

}

void Display_Deck(cards* deck) {
    for (int i = 0; i < SIZE; i++) {

        if (deck[i].suit == 0) {
            cout << "Diamond ";
        }
        else if (deck[i].suit == 1) {
            cout << "Heart ";
        }
        else if (deck[i].suit == 2) {
            cout << "Spade ";
        }
        else {
            cout << "Club ";
        }
        cout << " " << deck[i].power << endl;
        cout << endl;
    }
}

void Deck_Shuffler(cards* deck) {
    int changer = 0;               // Index of changed card
    cards temp = {};             // Temporary holding place for changing
    srand(time(NULL));            // Function to get random numbers with current time
    for (int i = 0; i < SIZE; i++) {
        changer = rand() % SIZE;   // Generating random number from 0 to 51
        temp = deck[i];
        deck[i] = deck[changer];  // if changer = i
        deck[changer] = temp;
    }
}

void Deck1_Creator(cards* deck, cards* deck1, decks* q_deck1) {
    for (int i = 0; i < HALF_SIZE; i++) {
        memcpy(&deck1[i], &deck[i], sizeof(cards));  // Copying content using memcpy function
    }
    q_deck1->p_deck = deck1;
    q_deck1->size = HALF_SIZE;
}

void Deck2_Creator(cards* deck, cards* deck2, decks* q_deck2) {
    int i = HALF_SIZE;
    for (int i = 26; i < SIZE; i++) {
        deck2[i - HALF_SIZE] = deck[i];   // Simple copying struct array content into another array
    }
    q_deck2->p_deck = deck2;
    q_deck2->size = HALF_SIZE;
}

void table_creator(decks* q_deck) {
    q_deck->p_deck = {};
    q_deck->size = 0;
}

void enqueue(decks* q_deck, cards card) {
    // I TRIED THAT TOO
    //int n;
    //n = q_deck->size;
    q_deck->p_deck[q_deck->size] = card;
    q_deck->size++;
}

cards* dequeue(decks* q_deck) {
    cards tmp_card;

    tmp_card = q_deck->p_deck[0];
    for (int i = 0; i < q_deck->size - 1; i++) {
        q_deck->p_deck[i] = q_deck->p_deck[i + 1];
    }
    q_deck->size--;

    return &tmp_card;
}

void disp_queue(decks* q_deck) {
    for (int i = 0; i < q_deck->size; i++) {
        cout << q_deck->p_deck[i].suit <<" ";
        cout << q_deck->p_deck[i].power << endl;
    }
}

int main() {                   
    cards deck[SIZE];
    cards deck1[SIZE];
    cards deck2[SIZE];
    cards table1[HALF_SIZE];
    cards table2[HALF_SIZE];
    decks q_deck1;
    decks q_deck2;
    decks q_table1;
    decks q_table2;
    char choice;

    table_creator(&q_table1);
    table_creator(&q_table2);

    for(; ;) {  //Never ending loop
        cin >> choice;
        switch (choice) {
        case '1':
            cout << endl << "Unshuffled deck: " << endl;
            Deck_Creator(deck);
            Display_Deck(deck);
            break;
        case '2':
            cout << endl << "Shuffled deck: " << endl;
            Deck_Shuffler(deck);
            Display_Deck(deck);
            break;
        case '3':
            cout << endl << "Hand 1:" << endl;
            Deck1_Creator(deck, deck1, &q_deck1);
            disp_queue(&q_deck1);
            break;
        case '4':
            cout << endl << "Hand 2:" << endl;
            Deck2_Creator(deck, deck2, &q_deck2);
            disp_queue(&q_deck2);
            break;
        case '5':
            cards tmp_card = *dequeue(&q_deck1);
            enqueue(&q_table1, tmp_card);
            tmp_card = *dequeue(&q_deck2);
            enqueue(&q_table2, tmp_card);
            disp_queue(&q_table1);
            disp_queue(&q_table2);
            break;
        case '6':
            disp_queue(&q_deck1);
            break;
        }
    }
    return 0;
}

ERROR 仅当我在 switch 函数中按下 case 5 时才会弹出。其余的都运作良好。此函数中出现错误:

cards* dequeue(decks* q_deck) {
    cards tmp_card;

    tmp_card = q_deck->p_deck[0];              // EXACTLY IN THIS LINE RED X OCCURS
    for (int i = 0; i < q_deck->size - 1; i++) {
        q_deck->p_deck[i] = q_deck->p_deck[i + 1];
    }
    q_deck->size--;

    return &tmp_card;
}

请帮助我理解这个错误，以便我完全知道为什么以及这个错误是如何工作的:(谢谢您的宝贵时间，我知道代码很长。

Answer 1

Yano 关于分配给 p_d​​eck 的内存不足的说法是正确的。我有点惊讶其他人竟然在工作(你似乎根本没有为这里的卡片分配任何空间，相反，你只是将卡片值写入指针旁边的区域，这在技术上并不重要属于您的指针，并且不保证保持不变)。

由于您使用的是 C++，因此您可以通过向处理分配内存的结构添加构造函数/析构函数来解决此问题。

typedef struct deck {
    cards* p_deck;
    int size;

    //constructor
    deck() : size(SIZE) //this sets the size to your size constant
    { 
        p_deck = malloc(size * sizeof(*p_deck)); //this gives p_deck memory space
    } 

    //destructor
    ~deck()
    {
        if(p_deck) delete[] p_deck; //this clears up the memory assigned to p_deck
        p_deck = nullptr;
    }

}deck; //edited so it matches the actual struct name

要使用构造函数，请在创建对象时使用 deck varName = Deck(); 而不是 deck varName;。

当对象超出范围时(在 main() 或其本地函数的末尾)，会自动调用析构函数。如果您出于某种原因想要释放内存(例如，如果您想重新创建一个全新的牌组)，也可以使用 varName.~deck();

手动调用它