c - 基于字符串比较的单词翻译程序——堆内存断言失败

Question

我制作了一个程序，它从文件 english_dictionary.txt 中读取 200 个最常用的英语单词，然后在 foreign_dictionary.txt 中我将这些单词的翻译放入相应的外语单词。

.txt 文件的内容放在两个 char * 类型的 200 元素数组中。

然后程序从文件 text_to_translate.txt 中读取，该文件包含英文文本，如果找到匹配项(这发生在compute_text 函数)。但它不起作用，我对堆内存断言失败，所以我想我用 malloc 或类似的东西出了问题，但我不明白我错在哪里。

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>

void foreign_dictionary(char **foreign, FILE *fp){

    char *buffer = malloc(30 * sizeof(char));
    char *tok;
    int i;

    for (i = 0; i < 200; ++i){
        fgets(buffer, 29, fp);
        tok = strtok(buffer, "\n");
        foreign[i] = malloc(strlen(tok) + 1);
        strcpy(foreign[i], tok);
    }

    free(tok);
    free(buffer);
}

void dictionary(char **english, FILE *fp){

    int i;
    char *tok;

    char *buffer = malloc(30 * sizeof(char));

    for (i = 0; i < 200; ++i){
        fgets(buffer, 29, fp);
        tok = strtok(buffer, " \n");
        english[i] = malloc(strlen(tok) + 1);
        strcpy(english[i], tok);
    }
    free(buffer);
    free(tok);
}

void compute_text(char **text,FILE *fp){

    char *buffer;
    int i, j, flag = 0, words_number = 0, cnt_letters_word = 0;

    buffer = malloc(100 * sizeof(char));

    while (fgets(buffer, 100, fp) != NULL){
        for (i = 0; i < 100; ++i){
            if (buffer[i] == ' ' || buffer[i] == '\0'){
                text[words_number] = malloc((cnt_letters_word + 1)* sizeof(char));
                for (j = 0; j < cnt_letters_word; ++j){
                    if (isupper(buffer[flag + j]))
                        text[words_number][j] = tolower(buffer[flag + j]);
                    else
                        text[words_number][j] = buffer[flag + j];
                }
                text[words_number][cnt_letters_word] = '\0';
                flag = i + 1;
                cnt_letters_word = 0;
                ++words_number;
            }
            else if (buffer[i] == '\n' || buffer[i] == ',' || buffer[i] == '.' || buffer[i] == ';' || buffer[i] == ':')
                ;
            else
                ++cnt_letters_word;
        }
        flag = 0;
        cnt_letters_word = 0;
    }
    free(buffer);
}

int main(void){

    char *foreign[200], *english[200], *text[50];

    FILE *fp = fopen("foreign_dictionary.txt", "r");
    foreign_dictionary(foreign, fp);
    fclose(fp);
    fp = fopen("english_dictionary.txt", "r");
    dictionary(english, fp);
    fclose(fp);
    fp = fopen("text_to_translate.txt", "r");
    compute_text(text, fp);
    fclose(fp);

    return 0;
}

Answer 1

在您的代码中，tok 没有指向动态分配的内存。你不需要(也不可能)free() 它。移除

 free(tok);

来自代码。

来自man page of free()

The free(ptr) function frees the memory space pointed to by ptr, which must have been returned by a previous call to malloc(), calloc() or realloc(). Otherwise, or if free(ptr) has already been called before, undefined behaviour. occurs.

就是说，在使用返回的指针之前，始终检查 fopen() 和 malloc()(可能还有所有库函数)的返回值以确保成功。