c - 在结构中对 char* 进行排序 - 获取垃圾

Question

我制作了一个 Node 结构数组，并尝试根据名为“word”的 char* 变量按字母顺序对节点进行排序。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "memwatch.h"
#include "concord.h"

#define BUFFSIZE 1000

int main(int argc, char** argv)
{
  Node** list;
  printf("%s%s\n","The file name is ",  argv[1]);
  readInputFile(argv[1], list);
  return 0;
}

int compareWords(const void* nodeA, const void* nodeB)
{
  Node* nodeAA = (Node *) nodeA;
  Node* nodeBB = (Node *) nodeB;
  puts("now here\n");
  printf("%s\n", nodeAA->word);
  printf("%s\n", nodeBB->word);
  return strcmp(nodeAA->word, nodeBB->word);
}

void readInputFile(char* filename, Node** wordList)
{
  FILE* file;
  file = fopen(filename, "r");
  wordList = calloc(BUFFSIZE, sizeof(Node*));

  char* currentWord;
  currentWord = (char*) malloc(sizeof(char) *BUFFSIZE);
  int i;
  i = 0;
  while(fscanf(file, "%s", currentWord)  == 1)
  {
    wordList[i] = (Node*) malloc(sizeof(Node));
    wordList[i]->word = strdup(currentWord);
    puts(wordList[i]->word);
  }
  fclose(file);
  qsort(wordList, i, sizeof(Node), compareWords);
}

在我尝试打印比较函数中的单词时打印出垃圾之前，现在看起来该函数甚至都没有被调用。

Answer 1

now it looks like the function is not even being called.

这是因为要对 0 元素的列表进行排序，您永远不需要比较两个元素:

  // ...
  int i;
  i = 0;    // --- set to 0
  while(fscanf(file, "%s", currentWord)  == 1)
  {
    // i not changed ... causes other problems, too
    // (contents omited)
  }
  fclose(file);
  // i is still 0
  qsort(wordList, i, sizeof(Node), compareWords);
  // ...

除此之外，您对“输出参数”的使用是错误的，正如 David C. Rankin 在评论中指出的那样。在这种情况下，我还建议只使用返回值。

此外，我将该函数拆分为多个函数:

// Does the file opening and closing, calls readInput
Node * readInputFile(char const *);
// The actual reading
Node * readInput(FILE *)
// Probably do the sorting outside of these functions