c - 段错误(核心转储)错误

Question

我正在编写一个程序，用于计算每个单词在文本文件中出现的次数。我收到一个运行时错误:段错误(核心已转储)。我知道这与尝试访问尚未分配的内存有关。

另外，我收到关于我对 getline 的争论的警告，我不确定我是否正确使用它。任何建议表示赞赏。

我的代码是:

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

#define MAXWORDS 5000
#define MAXLINE 1000
#define MAXWORDLEN 100


int count = 0;
struct wordcount *wordPtr[MAXWORDS];

typedef struct wordcount *wordcountptr;

typedef struct wordcount {
    char word[50];
    int count;
} wordcount_t;


main()
{

    int wordfound = 0;
    int len;
    char line[MAXLINE];
    int printcount;

    while ((len = getline(line, MAXLINE, stdin))> 0)
    {
        int i = 0;
        int j = 0;

        for( ; i<len; i++)
        {
            if(line[i] != isalnum(line[i]) && line[i] != 32)
                line[i] = 32;
            else
                line[i] = tolower(line[i]);
        }

        for( ; j<len; j++)
        {

            char currentword[MAXWORDLEN];

            if(line[j] != 32)
            {
                for(i=0; line[j] != 32; i++)
                    currentword[i] = line[j];
            }
            if(line[j] == 32)
            {
                for(i=0;i<MAXWORDS; i++)
                {
                    if(strcmp(currentword, (*wordPtr[i]).word) == 0)
                    {
                        (*wordPtr[i]).count++;
                        wordfound = 1;
                    }
                }

                if(wordfound == 0)
                {
                    wordPtr[i] = (wordcount_t*)malloc(sizeof(wordcount_t));
                    strcpy((*wordPtr[i]).word, currentword);
                    (*wordPtr[i]).count = 1;
                    count++;
                }
            }
            wordfound = 0;
        }
    }

    for(printcount = 0; printcount < count; printcount++)
        printf("There are %d occurances of the word %s\n", (*wordPtr[printcount]).count, (*wordPtr[printcount]).word);

    for(printcount = 0; printcount < MAXWORDS; printcount++)
    {
        free((void*)wordPtr[printcount]);
        wordPtr[printcount]= NULL;
    }
}

Answer 1

getline() 期望第一个参数是 char ** 类型，因此您应该这样调用它:

getline(&line, MAXLINE, stdin)

因为line是一个char数组，所以相当于char *而不是需要的char **。

引自this SO answer使用 char ** 而不是 char * 的原因是:

You need to pass in a char** (ie a pointer to a pointer to a char) so that the function is able to update the value of the char* that it points to.