Free（）如何与堆栈上包含在堆上制造的阵列的结构进行交互？

发布于 2025-02-03 04:24:23 字数 780 浏览 2 评论 0原文

假设我想创建一个包含图像数据的新结构

struct Image {
    int *pxl_arr;
    int pxl_arr_len;
    int img_wdt, img_hgt;
};

，并且我还具有单独的函数，该功能打开图像文件并将文件的内容复制到使用Malloc（）上在堆上制造的整数中可以解析该数据并将其与struct Image一起使用，

int *freadarr (char *fpath) {
    FILE *fptr;
    long len;
    int *buf;

 /* code to open file here */

    buf = (int *) malloc(len);

 /* code to read from file here */ 

    return buf;
}

然后在main（）函数的内部，我要这样做：

int main() {
    struct Image img;
    img.pxl_arr = freadarr(/* whatever the file path is */);
    free(img);
    return 0;
}

什么将free（）使用结构图像？

编辑：img.pxl_arr，不是img-＆gt; pxl_arr

原文

Say I want to create a new struct that contains image data

struct Image {
    int *pxl_arr;
    int pxl_arr_len;
    int img_wdt, img_hgt;
};

And I also had a separate function that opened an image file and copied the contents of the file into an array of integers made on the heap using malloc(), so that some other function could parse that data and use it with the struct Image

int *freadarr (char *fpath) {
    FILE *fptr;
    long len;
    int *buf;

 /* code to open file here */

    buf = (int *) malloc(len);

 /* code to read from file here */ 

    return buf;
}

Then inside of the main() function, I were to do this:

int main() {
    struct Image img;
    img.pxl_arr = freadarr(/* whatever the file path is */);
    free(img);
    return 0;
}

What would free() do with the struct Image?

EDIT: img.pxl_arr, not img->pxl_arr

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趴在窗边数星星i 2025-02-10 04:24:23

free（）对结构图像做什么？

没什么，因为您只能传递到免费从malloc返回的任何指针值（或calloc/realloc），或null。在您的（略有缺陷）示例中，这将是结构的pxl_arr持有的值。

也许任何，因为传递任何其他值是不确定的行为< /a>，但是您的编译器应大声投诉free（img）;：

main.c:12:10: error: incompatible type for argument 1 of ‘free’
   12 |     free(img);
      |          ^~~
      |          |
      |          struct Image

将指针值传递给免费完成后：

struct Image img;
img.pxl_arr = freadarr(/* whatever the file path is */);
/* ... do stuff .. */
free(img.pxl_arr);

请注意，请注意- ＆gt;用于通过指针访问结构的成员。 img不是指针，因此请使用。操作员。请参阅：成员访问操作员

What would free() do with the struct Image?

Nothing, as you should only pass to free any pointer value returned from malloc (or calloc / realloc), or NULL. In your (slightly flawed) example, that would be the value held by the pxl_arr member of the structure.

Or maybe anything, as passing any other value is Undefined Behaviour, but your compiler should complain loudly about free(img);:

main.c:12:10: error: incompatible type for argument 1 of ‘free’
   12 |     free(img);
      |          ^~~
      |          |
      |          struct Image

Pass the pointer value to free when you are done with it:

struct Image img;
img.pxl_arr = freadarr(/* whatever the file path is */);
/* ... do stuff .. */
free(img.pxl_arr);

Note that -> is for accessing the members of a structure via a pointer. img is not a pointer, so use the . operator. See: Member access operators

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