排列在结构中并填充他 [英] array in a struct and populate him

问题描述

目前，我有一个研究项目，而我和一个朋友真的不知道如何部分解决问题.

at the moment i have a project for the studies and me and a friend don't really know on how resolve the problem on a part of this.

所以，这是一个C项目.我有2个结构:

So, it's a C project. I have 2 struct :

struct Lib {
    char letter; 
    int capacity;
    int size; 
    char** words[200000];
};
typedef struct Lib Library;
struct Program {
    char* loadedFileName[50];
    FILE* f;
    Library* dictionary;
    int totalwords;
};

typedef struct Program Program;

此功能:

void fillDicoFromFile(Program* startup){
    rewind(startup->f);
    while(!feof(startup->f) && !ferror(startup->f)){
        char* word = malloc(sizeof(char) * 30);
        fscanf(startup->f, "%s", word);
        int indexLib = word[0] - 97;
        int sizeLib = startup->dictionary[indexLib].size;
        startup->dictionary[indexLib].words[sizeLib] = (char*)malloc(sizeof(char) * (strlen(word)+1));
        startup->dictionary[indexLib].words[sizeLib] = word;
        startup->dictionary[indexLib].size++;
        free(word);
    }
    CountTotalWords(startup);
}

startup-> dictionary是一个由26个Library组成的数组，当我从文件中得到一个单词时，我检查他的第一个字母并选择好的Library(startup-> dictionary [0]表示'a'...)然后将该单词放在该结构的数组单词"上，但是当我想要printf一些单词时，它就是错误的字符串或错误的字符串.我很确定我们在指针上做错了，但是在哪里...

startup->dictionary is a array of 26 Library, and when i get a word from the file, i check his first letter and select the good Library (startup->dictionary[0] for 'a' ...) and then put the word on the array "word" of the struct, but when i want printf some words, it's bugged strings or wrongs one. I'm pretty sure we're doing wrong on pointers but where ...

我们在做什么错了?

推荐答案

此:

    startup->dictionary[indexLib].words[sizeLib] = (char*)malloc(sizeof(char) * (strlen(word)+1));
    startup->dictionary[indexLib].words[sizeLib] = word;

...没有按照您的想法做.您正在分配空间(使用malloc，第一行)，但是没有使用它.而是在word(第二行)中存储指向先前分配的空间的指针.需要明确的是，语句startup->dictionary[indexLib].words[sizeLib] = word不会复制字符串；它会复制字符串.它只是分配一个指针.

... doesn't do what you think it does. You are allocating space (using malloc, the first line), but you are not using it; instead, you are storing a pointer to the previously allocated space in word (the second line). To be clear, the statement startup->dictionary[indexLib].words[sizeLib] = word will not copy a string; it is just assigning a pointer.

然后，您释放该空间:

    free(word);

词典现在包含一个悬挂指针-指向不再分配的区域的指针.解决方法很简单:

The dictionary now contains a dangling pointer - a pointer to an area that is no longer allocated. The fix is easy:

1. 删除上面的第一行(使用malloc)；您不需要为已经分配了空间的单词分配空间
2. 删除free(word)行；您不希望取消分配此空间，因为它是由字典结构引用的.

1. Remove the first line above (which uses malloc); you don't need to allocate space for a word that you've already allocated space for
2. Remove the free(word) line; you don't want to deallocate this space, since it is being referred to by the dictionary structure.

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