Question

我需要修改现有的API，基本上，我唯一的选择就是通过函数参数返回指向不规则数组的指针（这通常不是我的个人喜好）。我无法全力以赴，并在此部分代码中不断遇到分段错误：

void getMxByArg(int ***pppX) {
    *pppX = m_ppMx; // SEGMENTATION FAULT HERE
}

我在下面提供了一个示例，该示例没有任何外部依赖关系，并封装了问题。

#include <stdint.h>
#include <iostream>

using namespace std;


class Mx {
public:
    Mx() {
        int *buff01 = (int*)malloc(3 * sizeof(int));
        int *buff02 = (int*)malloc(3 * sizeof(int));

        buff01[0] = 0;
        buff01[1] = 1;
        buff01[2] = 3;

        buff02[0] = 4;
        buff02[1] = 5;
        buff02[2] = 6;

        m_n = 2;
        m_ppMx = (int**)malloc(m_n * sizeof(int*));
        m_ppMx[0] = buff01;
        m_ppMx[1] = buff02;
    }

    ~Mx() {
        for (int i=0; i<m_n; ++i) {
            free(m_ppMx[i]);
        }
        free(m_ppMx);
    }

    int** getMx() {
        return m_ppMx;
    }

    void getMxByArg(int ***pppX) {
        *pppX = m_ppMx; // SEGMENTATION FAULT HERE
    }

private:
    int **m_ppMx;
    int m_n;
};

int main()
{
    Mx mx;

    // SUCCESS
    int **ppX = mx.getMx();

    // FAILURE, Results in segmentation fault in getMxByArg
    int ***pppX;
    mx.getMxByArg(pppX);

    return 0;
}

Answer 1

在发布的代码中，您要取消引用未初始化的指针。这是导致行为不确定的原因。

解决方案是：

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将该变量的地址传递给函数。

int**

另一种选择是将参数类型更改为int **ppX2; mx.getMxByArg(&ppX2);。

int**&

然后，您可以使用：

void getMxByArg(int**& ppX) {
    ppX = m_ppMx;
}

如何通过函数参数返回指向粗糙数组的指针？

1 个答案: