C 中的段错误（在 for 循环中间）

Question

我正在尝试通过编写记忆型纸牌游戏来练习C。该游戏由 gcc 在 ARMv8 上编译。用户在参数行中输入一个数字“users_N”，然后创建一副纸牌大小：2N x 2N。

程序在数字为 1 或 2 时运行良好。但如果数字为 3 或更大，我在尝试初始化电路板时遇到分段错误。我认为这意味着它是堆栈溢出，但我在我的 SSH 上将堆栈大小增加到无限，但问题没有解决。我不认为这是指针或尝试越界访问数组的问题，因为它运行得很好，直到将 10 张卡片添加到数组中。

打印语句只是为了确定段错误发生的确切时间。See image of for loop segfault

编辑：添加更多上下文...我知道它有点乱，抱歉！

int main(int argc, char *argv[]) {
    if (argc < 3){          //Checking user's command line input.
        printf("Missing argument. Exiting...    \n");
            return 0;
    }   
    users_N = atoi(argv[2]);
    srand(time(NULL));   //Initialize random number generator.
    int ***board = (int ***)malloc(2 * users_N * sizeof(int));  //Dynamic array to store the board values
    for (int i = 0; i < 2 * users_N; i++){
        board[i] = (int **)malloc(2 * users_N * sizeof(int)); /*Array of pointers (rows) filled with
                                                              an array (columns). */
        for (int j = 0; j < 2 * users_N; j++){
            board[i][j] = (int *)malloc(2 * sizeof(int)); //3rd dimension to show/hide cards.
        }
    }
    initialize(board);  
}

 /*
 * Function initialize sets up the board. It takes the 3D  board array. A card deck is created the
 * size of 2N^2, then shuffled and added to the board. The 3rd dimension is initialized
 * completely to 1, so all cards are shown. There is no return. 
 */
void initialize(int*** board){
    int* cards = (int *)malloc(2 * users_N * users_N * sizeof(int)); //Create an array of cards.
    printf("Cards created\n");

    for (int c = 0; c < (2 * users_N * users_N); c++){
        printf("card: %d\n",c);
        cards[c]=c;
    }
    int half = 0;
    
    while (half < 2){   //Divide up into 2 halves of the board, to repeat shuffle and card placement.
        shuffle(cards);
        int cardsNum = 0;
        for (int j = 0; j < users_N; j++){  //For each row in the current half:
            printf("\n row = %d ", j);
            for (int k = 0; k < (users_N * 2); k++){    //For each column:
                printf("col = %d ",k);


                board[j + (half * users_N)][k][0] = cards[cardsNum];  /* Assign appropriate
                                              card to each board 
                                              position. */
                printf("set to: %d ", board[j + (half * users_N)][k][0]);
                board[j + (half * users_N)][k][1] = 1;
                cardsNum++;
                printf("Card num: %d \n", cardsNum);
            }
        }
        half++;     //Moves to next half to repeat.
    }
}
/*
 * Function shuffle takes the array of cards as a parameter. It will then randomly mix array.
 * Numbers are not repeated and will not exceed 2N*N-1. No return values.
 */
void shuffle(int *cards){
    int j;
    for (int k = 0; k < (2 * users_N * users_N) - 2; k++){
        j = randomNum(k, (2 * users_N * users_N) - 1); //Assign a random number between k and 2N*N-1.
        swap(cards, k, j);
        printf("cards swapped: %d,%d\n",k,j);
    }   
}

/*
 * Function swap takes the array of cards, two index integers. The index integers indicate the positions of
 * the elements (cards) to switch. No return values.
 */
void swap(int *cards, int i, int j){
    int temp = cards[i];    //Value of position i stored in temp.
    cards[i] = cards[j];    //value of card j assigned to card i.
    cards[j] = temp;        //Value of temp assigned to card j.
}

Answer 1

你的板子分配错误：

int ***board = (int ***)malloc(2 * users_N * sizeof(int));
                                             ^^^^^^^^^^^
                                             wrong size


for (int i = 0; i < 2 * users_N; i++){
    board[i] = (int **)malloc(2 * users_N * sizeof(int));
                                             ^^^^^^^^^^^
                                             wrong size
    ...

}

当您将 board 作为 int *** 时，您不希望在第一次分配期间使用 int 的大小。您想要 int ** 的大小。喜欢

int ***board = malloc(2 * users_N * sizeof(int**));

更好的方法是使用变量名——例如：

int ***board = malloc(2 * users_N * sizeof *board);
                                           ^^^^^^
                                          Better approach
                                          to get correct size

下一个也一样malloc

C 中的段错误（在 for 循环中间）

Segfault in C (during middle of for loops)

c

gcc

segmentation-fault

nested-for-loop