在VSCode中编写C语言Hangman游戏时while循环出现Segmentation Fault

直接触发段错误的原因 #

代码最开头的while (fgets(buf, LEN, fp))完全是多余的，而且此时buf和fp都还没定义——这两个变量是在这个循环体内部才声明的。未初始化的fp是野指针，直接调用fgets会访问非法内存，立刻触发段错误，直接删掉这行外层循环即可。

其他潜在问题及修复要点 #

• 必须检查文件打开结果：fopen可能因为文件不存在、权限问题返回NULL，后续操作野指针必然崩溃，添加检查：

  FILE *fp = fopen("dictionary.txt", "r");
  if (fp == NULL) {
      perror("Failed to open dictionary");
      return NULL;
  }
  

• 扩容逻辑错误：原代码判断dictionary->nval > dictionary->max才扩容，当nval等于max时数组已经满了，再添加元素会越界，改成dictionary->nval >= dictionary->max。
• strtok使用隐患：strtok会修改原字符串，而且如果行尾没有换行符会返回整个buf，改用strcspn更安全地去除换行：

  buf[strcspn(buf, "\n")] = '\0';
  

• nval计数错误：循环结束后dictionary->nval--完全没必要，每次循环nval已经正确自增，减1会导致少统计一个单词，直接删掉这行。
• 初始值优化：dictionary->nval初始设为0更合理，和实际添加的单词数同步。

修复后的完整代码示例 #

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

#define LEN 100
#define INIT 1
#define GROW 2

struct diction_t {
    int nval;
    int max;
    char **words;
};

struct diction_t *load_dictionary() {
    char buf[LEN];
    FILE *fp = fopen("dictionary.txt", "r");
    if (fp == NULL) {
        perror("Failed to open dictionary");
        return NULL;
    }

    struct diction_t *dictionary = malloc(sizeof(struct diction_t));
    assert(dictionary);

    dictionary->nval = 0;
    dictionary->max = INIT;
    dictionary->words = malloc(sizeof(char *) * dictionary->max);
    assert(dictionary->words);

    int i = 0;
    while (fgets(buf, LEN, fp)) {
        buf[strcspn(buf, "\n")] = '\0';
        
        if (dictionary->nval >= dictionary->max) {
            size_t new_capacity = GROW * dictionary->max;
            char **temp = realloc(dictionary->words, new_capacity * sizeof(char *));
            assert(temp);
            dictionary->words = temp;
            dictionary->max = new_capacity;
        }

        dictionary->words[i] = malloc(strlen(buf) + 1);
        assert(dictionary->words[i]);
        strcpy(dictionary->words[i], buf);

        i++;
        dictionary->nval++;
    }

    fclose(fp);
    return dictionary;
}

内容的提问来源于stack exchange，提问作者IV6IX