通过指针访问数组时出现分段错误

Question

我有一个全局数组声明为

int Team1[12][8];

当我调用函数时

int readLineupB(int teamNr){

      int (*teamToRead)[12][8];
      teamToRead = &Team1;

      for (int currentPlayersNumber = 1; currentPlayersNumber<11; currentPlayersNumber++) {
        for (int otherNumber = 1; otherNumber<7; otherNumber++) {
            *teamToRead[currentPlayersNumber][otherNumber] = 20;
        }
    } 
    return 1;
}

它填充数组直到位置 [10]，[3]，然后似乎对于 [10]，[4] 我得到了一个分段错误，我不明白为什么。

Answer 1

检查数据类型。

teamToRead 是指向 int [12][8] 数组的指针。

由于 operator precedence，下标运算符的绑定高于取消引用。

所以，如果

  *teamToRead[currentPlayersNumber][otherNumber] = 20;

你想说的是

  *(* ( teamToRead + currentPlayersNumber ) ) [otherNumber] = 20;

其中，指针运算变得非法，因为它们遵循指针类型并因此冒险越界。

要解决这个问题，您需要通过显式括号强制取消引用的优先级，例如

 (*teamToRead)[currentPlayersNumber][otherNumber] = 20;

Answer 2

另一种选择是放弃指向二维数组的指针，而只使用指向一维数组（数组的第一个）的指针：

int Team1[12][8];

int readLineupB(int teamNr){
    // declare teamToRead as a pointer to array of 8 ints
    int (*teamToRead)[8];

    // Team1 is of type int x[12][8] that readily decays 
    // to int (*x)[8]
    teamToRead = Team1;

    for (int currentPlayersNumber = 1; currentPlayersNumber<11; currentPlayersNumber++) {
        for (int otherNumber = 1; otherNumber<7; otherNumber++) {
            // no dereference here.
            teamToRead[currentPlayersNumber][otherNumber] = 20;
        }
    }
    return 0;
}

通过指针访问数组时出现分段错误

Segmentation fault when accessing array via pointer

c

arrays

pointers

operator-precedence