c中結構指標內的雙陣列

為什么這個雙映射陣列幾乎可以作業，但不行？

我的代碼如下：

#include <stdlib.h>
#include <stdio.h>

typedef struct {
    double mapping [3][3];
} CoordinateMapperStr;
typedef CoordinateMapperStr * CoordinateMapper;

CoordinateMapper CoordinateMapper_Constructor(void)
{
    CoordinateMapper this = (CoordinateMapper) calloc (1, sizeof(CoordinateMapper));
    //return this; // <- I was missing this return, but still the rest worked the same
}

void CoordinateMapper_Initialize(CoordinateMapper this, double numb)
{
    for (int i=0; i < 3; i=i 1) {
        for (int j=0; j < 3; j=j 1) {
            this->mapping[i][j] = numb;
            printf("mapping(%d, %d) = %f\n", i, j, this->mapping[i][j]);
        }
    }
}

void CoordinateMapper_Print(CoordinateMapper this)
{
    for (int i=0; i < 3; i=i 1) {
        for (int j=0; j < 3; j=j 1) {
            printf("mapping(%d, %d) = %f\n", i, j, this->mapping[i][j]);
        }
    }
}

int main()
{
    CoordinateMapper mapper_1 = CoordinateMapper_Constructor();
    CoordinateMapper_Initialize(mapper_1, 1);
    printf("Init 1 done\n");

    CoordinateMapper_Print(mapper_1);
    printf("Print 1 done\n");

    CoordinateMapper mapper_2 = CoordinateMapper_Constructor();
    CoordinateMapper_Initialize(mapper_2, 2);
    printf("Init 2 done\n");

    CoordinateMapper_Print(mapper_1);
    printf("Second print 1 done\n");

    CoordinateMapper_Print(mapper_2);
    printf("Print 2 done\n");
}

// Here is the corresponding output
user:~/path$ gcc src/test_3.c -o test_3
user:~/path$ ./test_3
mapping(0, 0) = 1.000000
mapping(0, 1) = 1.000000
mapping(0, 2) = 1.000000
mapping(1, 0) = 1.000000
mapping(1, 1) = 1.000000
mapping(1, 2) = 1.000000
mapping(2, 0) = 1.000000
mapping(2, 1) = 1.000000
mapping(2, 2) = 1.000000
Init 1 done
mapping(0, 0) = 1.000000
mapping(0, 1) = 1.000000
mapping(0, 2) = 1.000000
mapping(1, 0) = 1.000000
mapping(1, 1) = 0.000000 // This is not correct
mapping(1, 2) = 0.000000 // This is not correct
mapping(2, 0) = 0.000000 // This is not correct
mapping(2, 1) = 1.000000
mapping(2, 2) = 1.000000
Print 1 done
mapping(0, 0) = 2.000000
mapping(0, 1) = 2.000000
mapping(0, 2) = 2.000000
mapping(1, 0) = 2.000000
mapping(1, 1) = 2.000000
mapping(1, 2) = 2.000000
mapping(2, 0) = 2.000000
mapping(2, 1) = 2.000000
mapping(2, 2) = 2.000000
Init 2 done
mapping(0, 0) = 1.000000
mapping(0, 1) = 1.000000
mapping(0, 2) = 1.000000
mapping(1, 0) = 1.000000
mapping(1, 1) = 0.000000 // This is not correct
mapping(1, 2) = 0.000000 // This is not correct
mapping(2, 0) = 0.000000 // This is not correct
mapping(2, 1) = 1.000000
mapping(2, 2) = 1.000000
Second print 1 done
mapping(0, 0) = 2.000000
mapping(0, 1) = 2.000000
mapping(0, 2) = 2.000000
mapping(1, 0) = 2.000000
mapping(1, 1) = 2.000000
mapping(1, 2) = 2.000000
mapping(2, 0) = 2.000000
mapping(2, 1) = 2.000000
mapping(2, 2) = 2.000000
Print 2 done

1. 在結構指標中設定雙陣列的正確方法是什么？
2. 為什么每個結構指標似乎都成為自己的新陣列，但它們仍然有點不穩定？
3. 我gcc可以使用哪些編譯器標志來幫助我查看此類錯誤以及return this;建構式中的缺失？

uj5u.com熱心網友回復：

問題在于，無論您是否return this這樣做，在任何一種情況下都會出現未定義的行為。

當您不這樣做時，return this您的非 void 函式不會回傳值——因此您的代碼使用了一些垃圾值（這可能恰好是 的回傳值calloc）。

如果您return this- 您回傳分配的sizeof(CoordinateMapper)，這只是單個指標的大小。這小于您的 struct sizeof(CoordinateMapperStr)，并且您的其他代碼讀取/寫入超出分配的記憶體。這又是未定義的行為。

uj5u.com熱心網友回復：

@YakovGalka 發現了我的錯誤。我想在這里補充一點，valgrind 確實是一個可以檢測此類編程錯誤的工具。通過添加-Wall并-g以gcc如編譯器標志和運行與應用程式valgrind ./compiled_app，然后很容易被檢測到這些型別的錯誤。

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