malloc初始化二维数组时出现c分割错误

Question

我的程序由于分段错误而失败。使用gdb，我可以看到问题是在初始化函数中的2d数组时。

我的编译器标志是-Wall -Wpedantic -Wextra -Wconversion -std=gnu11

这是我正在使用的函数。第4行出现错误。我不明白为什么它会在那里坏掉，我对C.相当陌生

1 char ** get_categories_names(char * file_route, unsigned int maximum_categories) {
2     unsigned int category_counter = 0;
3
4     char ** categories_list = (char **)malloc(maximum_categories * sizeof(char *));
5     char * category = "";
6     FILE * categories_config;
7     categories_config = fopen(file_route, "r");
8
9     if (categories_config == NULL)
10    {
11            perror("Error while opening the file.n");
12            exit(EXIT_FAILURE);
13    }
14
15    while (fgets(category, 255, categories_config) && category_counter < maximum_categories) {
16            printf("%d", category_counter);
17            categories_list[category_counter] = malloc(100 * sizeof(char));
18            category[strcspn(category, "n")] = 0;
19            categories_list[category_counter] = category;
20            category_counter++;
21    }
22    fclose(categories_config);
23    return categories_list;

这是gdb的结果：

(gdb) step
11              char ** categories_list = (char **)malloc(maximum_categories * sizeof(char *));
(gdb) step
__GI___libc_malloc (bytes=40) at malloc.c:3028
3028    malloc.c: No existe el archivo o el directorio.

这是我读到的文本文件：

horror
mystery
FPS
memes
comedy

Answer 1

存在许多问题。我会尝试在你的代码中添加关于原因的注释。请注意，我没有编译，所以可能有一些打字错误

char ** get_categories_names(char * file_route, unsigned int maximum_categories) {
unsigned int category_counter = 0;
// don't cast the result of malloc
char ** categories_list = malloc(maximum_categories * sizeof(char *));
// declare category as array to provide memory for fgets()
char category[255];
FILE * categories_config;
categories_config = fopen(file_route, "r");
if (categories_config == NULL)
{
perror("Error while opening the file.n");
exit(EXIT_FAILURE);
}
// use sizeof array so you don't have to repeat array size
while (fgets(category, sizeof category, categories_config) && category_counter < maximum_categories) {
printf("%d", category_counter);

category[strcspn(category, "n")] = 0;
// alloc the right size -- sizeof( char ) is always 1 and can be omitted
categories_list[category_counter] = malloc(strlen(category)+1);
// copy strings w/ strcpy()
strcpy(categories_list[category_counter], category);
// the two commands above could be replaced by
//categories_list[category_counter] = strdup(category);
category_counter++;
}
fclose(categories_config);
return categories_list; 

此外，malloc()可以返回NULL。也应该检查一下

Answer 2

关于；

(gdb) step
11              char ** categories_list = (char **)malloc(maximum_categories * sizeof(char *));
(gdb) step
__GI___libc_malloc (bytes=40) at malloc.c:3028
3028    malloc.c: No existe el archivo o el directorio.

这并不是说发生了seg故障事件。

相反，它是说您没有gdb可见的malloc.c的源代码

为了避免这种问题，建议：

(gdb) step
11              char ** categories_list = (char **)malloc(maximum_categories * sizeof(char *));
(gdb) next

它将执行对malloc()的调用，但直到代码中的下一条语句才停止