c - C中使用指针的动态字符串数组

Question

我是 C 语言的新手。我使用动态字符串数组。我想将文本文件中的所有单词加载到一个字符串数组中。我动态地将项目添加到数组中。它几乎可以工作，但是当我想将它们打印出来时，我重复了单词。我认为问题出在 dictionary = (char **)realloc(dictionary, sizeof(char *) * (idx)); 复制原始数据后数组应该增加 1。

int main() {

    FILE *fr;
    int i = 0;
    int c;
    const char *path = "..../sample.txt";
    char *word;
    char **dictionary;
    word = (char *)malloc(sizeof(char));
    dictionary = (char **)malloc(sizeof(char *));

    int idx = 0;    // index of word
    int widx = 0;   // index of char in word

    fr = fopen(path, "r");
    while((c = getc(fr)) != EOF){
        if( c == ' '){
            widx++;
            word = (char *)realloc(word, sizeof(char) * (widx));
            *(word + widx-1) = '\0';
            idx++;
            dictionary = (char **)realloc(dictionary, sizeof(char *) * (idx));
            *(dictionary+idx-1) = word;
            widx = 0;
            word = (char *)realloc(word, 0);
        }
        else if( c == '.' || c == ',' || c == '?' || c == '!' ){
            // skip
        }
        else{
            widx++;
            word = (char *)realloc(word, sizeof(char) * (widx));
            *(word + widx-1) = (char)c;
        }
    }
    fclose(fr);

    // print words
    int n = idx;
    for(i = 0; i < n; i++){
        printf("%d - %s \n", i, *(dictionary+i));
    }
    return 0;
}

输出:

0 - shellbly 
1 -  
2 - shellbly 
3 - Bourne-derived 
4 - shellbly 
5 - Bourne-derived 
6 - shellbly 
7 - Bourne-derived 

预期:

1 - The 
2 - original 
3 - Bourne 
4 - shell 
5 - distributed 
6 - with 
7 - V7 
8 - Unix 

我一定做错了什么。感谢您的任何反馈。

Answer 1

realloc(word, 0) 等同于free(word)。但是该指针 word 与您刚刚存储为 dictionary 元素的指针相同，这意味着访问 dictionary 的指针元素不再有效>.

除了word = realloc(word, 0);，你可以只做word = NULL;。这将导致下一个 realloc 分配新的存储空间，并将指针单独留在 dictionary 中。

如果您担心正确清理您分配的内存，您稍后可以释放 dictionary 中的所有有效指针。