c - 链表 C 程序导致段错误 :11

Question

我有一个程序，我正在为一项任务而工作。这必须是一个链表，它从文件中逐个字符地读取，然后创建单词，然后将这些单词写入输出文件。我能够在没有错误的情况下编译代码。当我尝试使用 input.txt 和 output.txt 运行程序时，程序运行，然后终端生成第一行，即 file opened 后跟 segmentation fault:11 我不知道如何解决这个问题或解决它以修复它。

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

typedef struct s_words {
    char *str;
    int count;
    struct s_words* next;  
}
words;

words *create_words(char *word) {
    //allocate space for the structure
    words *newWord = malloc(15);
    if (NULL != newWord) {
        //allocate space for storing the new word in "str"
        //if str was array of fixed size, storage would be wasted
        newWord->str = (char *)malloc(strlen(word));
        strcpy(newWord->str, word); //copy word into newWord->str
        newWord->str[strlen(word)] = '\0';
        newWord->count = 1;   //initialize count to 1;
        newWord->next = NULL; //initialize next;
    }
    return newWord;
}

words *add_word(words *wordList, char *word) {
    int found = 0;
    words *temp = wordList;
    // search if word exists in the list; if so, make found=1
    while (temp != NULL) {
        if (strcmp(temp, word)) {  //use strcmp command
            found = 1;
            wordList->count++; //increment count;
            return wordList;
        } else {
            temp = temp->next;  //update temp
        }
    }
    if (found == 0) {  //new word
        words *newWord = create_words(word); 
        if (NULL != newWord) {
            wordList = newWord;
            newWord->next = temp;
            //??  Insert new word at the head of the list
        }
        return newWord;
    }
}

int main(int argc, char *argv[]) {
    words *mywords;  //head of linked list containing words
    mywords = NULL;

    FILE *myFile;
    myFile = fopen(argv[0], "r");  //first parameter is input file
    if (myFile == 0) {
        printf("file not opened\n");
        return 1;
    } else {
        printf("file opened \n");
    }

    //start reading file character by character;
    //when word has been detected; call the add_word function
    int ch, word = 0, k = 0;
    char thisword[100];
    while ((ch = fgetc(myFile)) != EOF) {
        if (ch == ' ') { //detect new word? Check if ch is a delimiter
            if (word == 1) { //make sure previous character was not delimiter
                printf("hi");
                word = 0;
                thisword[k] = '\0'; //make the kth character of thisword as \0

                add_word(mywords, thisword);   //now call add_word to add thisword into the list
                mywords = NULL;
                k = 0;
            }
        } else {
            word = 1;
            thisword[k] = ch; //make the kth character of thisword equal to ch
            k++;
        }
    }
    fclose(myFile); 

    words *currword;
    printf("printing list\n");

    words *temp;
    //Traverse list and print each word and its count to outputfile
    //output file is second parameter being passed

    FILE *outputFile;
    outputFile = fopen(argv[1], "w");
    if (outputFile == 0) {
        printf("file not opened\n");
        return 1;
    } else {
        printf("file opened \n");
    }

    currword = mywords;

    while (currword != NULL) {
        fprintf(outputFile, "HI");
        fprintf(outputFile, "%s %d" , currword, currword->count);
        temp = currword;
        currword = temp->next;
    }
    return 0;
}

任何帮助将不胜感激

编辑这是更新后的代码:CODE

新的输出现在是这样的:这是文件 test.txt results.txt 文件打开hihihihihihihihihihihihihihi打印列表文件未打开中止陷阱:6

Answer 1

您在 word 结构中分配字符串的方式不正确:

        newWord->str = (char *)malloc(strlen(word));
        strcpy(newWord->str, word); //copy word into newWord->str
        newWord->str[strlen(word)]='\0';

您必须为 '\0' 终止符再分配一个字节:

        newWord->str = malloc(strlen(word) + 1);
        strcpy(newWord->str, word);

您可以通过一次调用 strdup() 来简化此过程:

        newWord->str = strdup(word);

此外，您调用strcmp(temp, word) 将单词与当前条目的字符串进行比较，这是不正确的，编译器必须针对此错误发出警告。你应该改为写:

    if (strcmp(temp->str, word)) {

在 main() 中，您错误地调用了 add_word():

    add_word(mywords, thisword);   //now call add_word to add thisword into the list
    mywords = NULL;

你应该写:

    mywords = add_word(mywords, thisword);   //now call add_word to add thisword into the list

在打印循环中，您将 currword 传递给 printf for %s 而不是 currword->str .您也不需要额外的 temp 变量:

while (currword != NULL) {
    fprintf(outputFile, "HI");
    fprintf(outputFile, "%s %d" , currword->str, currword->count);
    currword = currword->next;
}

编辑:您的函数 add_word 并不总是向调用者返回一个值，并且它没有在列表的开头正确插入 newWord。

修改后的版本:

words *add_word(words *wordList, char *word) {
    // search if word exists in the list; if update count and return
    for (words *temp = wordList; temp != NULL; temp = temp->next) {
        if (strcmp(temp, word)) {  //use strcmp command
            wordList->count++; //increment count;
            return wordList;
        }
    }
    words *newWord = create_words(word); 
    if (newWord != NULL) {
        // Insert new word at the head of the list
        newWord->next = wordList;
        wordList = newWord;
    }
    return newWord;
}

最后，出现段错误的原因可能是您在从输入文件中读取时向数组添加字符时没有检查数组大小。您可能想知道为什么，因为输入文件中可能包含小字……但是您没有读取作为第一个命令行参数传递的输入文件，而是在读取可执行文件本身时执行此操作:

myFile = fopen(argv[0], "r");  //first parameter is input file

argv[0] 是执行程序的名称。

您还应该更改其他 fopen，否则您将覆盖您的 input.txt 文件:

myFile = fopen(argv[1], "r");  //first parameter is input file
...
outputFile = fopen(argv[2], "w"); // second parameter is output file