使用指针访问结构成员的垃圾数据

Question

struct _StoryElement_ { 
char *title_of_chapter_; 
struct _StoryElement_ *path_a_; 
struct _StoryElement_ *path_b_; 
char *content_of_chapter_; 
}; 
typedef struct _StoryElement_ StoryElement; 

因此，我创建了一个Tree，其中每个Structs都包含不同的值。我初始化它们都使用以下功能：

StoryElement *insertIntoStoryElement(StoryElement* root, char* title_of_chapter, char* content_of_chapter) 
{ 
    if(root == NULL) 
    { 
    root = makeNewStoryElement(root, title_of_chapter, content_of_chapter); 
    } 
    else if (root->path_a_ == NULL) 
    { 
    root->path_a_ = makeNewStoryElement(root, title_of_chapter, content_of_chapter); 
    } 
    else if (root->path_b_ == NULL) 
    { 
    root->path_b_ = makeNewStoryElement(root, title_of_chapter, content_of_chapter); 
    } 

    return root; 
} 

StoryElement *makeNewStoryElement(StoryElement* root, char* title_of_chapter, 
            char* content_of_chapter) 
{ 
    root = (StoryElement*) malloc(sizeof(StoryElement)); 

    root->title_of_chapter_ = 
    (char*)malloc(sizeof(char*)*(strlen(title_of_chapter) + 1)); 
    root->content_of_chapter_ = 
    (char*)malloc(sizeof(char*)*(strlen(title_of_chapter) + 1)); 

    //strcpy(NewStoryElement->title_of_chapter_, title_of_chapter); 
    //strcpy(NewStoryElement->content_of_chapter_, content_of_chapter); 
    title_of_chapter = root->title_of_chapter_; 
    content_of_chapter = root->content_of_chapter_; 

    root->path_a_ = NULL; 
    root->path_b_ = NULL; 

    return root; 
} 

此功能就是为我提供了我转嫁给insertIntoStoryElement（）的字符串值：

StoryElement *createStoryTree (StoryElement *root, char *storage) 
{ 

    char* pos = storage; 
    pos = strchr(pos, '\n'); 
    *pos = '\0'; 
    int size = strlen(storage); 
    char* title = malloc(size + 1); 
    strcpy(title, storage); 

    char* ptr_path_a = pos + 1; 
    pos = strchr(ptr_path_a, '\n'); 
    *pos = '\0'; 
    size = strlen(ptr_path_a); 
    char* path_a = malloc(size + 1); 
    strcpy(path_a, ptr_path_a); 

    char* ptr_path_b = pos + 1; 
    pos = strchr(ptr_path_b, '\n'); 
    *pos = '\0'; 
    size = strlen(ptr_path_b); 
    char* path_b = malloc(size + 1); 
    strcpy(path_b, ptr_path_b); 

    char* ptr_text = pos + 1; 
    pos = strchr(pos + 1, '\0'); 
    *pos = '\0'; 
    size = strlen(ptr_text); 
    char* text = malloc(size + 1); 
    strcpy(text, ptr_text); 

    root = insertIntoStoryElement(root, title, text); 

/* if(strcmp(path_a, "-")!=0 && strcmp(path_b, "-")!=0) 
    {*/ 
    root->path_a_ = readStoryFromFile(root->path_a_, path_a); 
    root->path_a_ = readStoryFromFile(root->path_b_, path_b); 
    //} 

    return root; 
} 

这是最终调用的函数主：

StoryElement *readStoryFromFile (StoryElement *root, char *filename) 
{ 
    if(strcmp(filename, "-") == 0) 
    { 
    //printf("End reached\n"); 
    return 0; 
    } 
    FILE *file = fopen(filename, "r"); 

    if(!file) 
    { 
    printf("[ERR] Could not read file %s.\n", filename); 
    return 0; 
    } 

    long fsize = getFileSize(file); 

    char* storage = malloc(fsize + 1); 
    if(!storage) 
    { 
    printf("[ERR] Out of memory.\n"); 
    return 0; 
    } 

    fread(storage, fsize, 1, file); 
    storage[fsize] = '\0'; 
    fclose(file); 

    root = createStoryTree(root, storage); 

    free(storage); 

    return root; 
} 

这是我的主要它使用另一种功能，仅高于2是相关的这个问题，我认为：

int main (int argc, char *argv[]) 
{ 
    if (argc != 2) /* argc should be 2 for correct execution */ 
    { 
    printf("Usage: ./ass2 [file-name]\n"); 
    return (1); 
    } 

    StoryElement *root = NULL; 

    root = readStoryFromFile(root, argv[1]); 
    if(!root) 
    return 3; 

    printf("%p\n", root); 
    printf("%s\n", root->title_of_chapter_); 

    //printStoryTree(root); 
    freeStoryTree(root); 

    root = NULL; 

    return 0; 
} 

最后我的问题是，2个printfs输出后，在主函数返回以下内容： First pointer Address is ok I think, but the second printf should be "Kapitel_1.txt" 我为什么在这里得到一个垃圾的价值？这是分段错误吗？

Answer 1

在您的函数makeNewStoryElement中malloc为root->title_of_chapter指定的空间，但是您不会将给定的title_of_chapter的内容放入其中。这意味着root->title_of_chapter将包含您从malloc返回的位置中的任何垃圾数据。
做一些类似于 strcpy(root->title_of_chapter, title_of_chapter);
printf将会很好。
该代码还有其他一些问题和你不应该做的事情，但是这应该解决你所问的问题。