我知道分段错误(核心转储)错误是因为我试图访问我无权访问的内存,但我不明白为什么它会对我的程序造成影响。我确定问题出在printList(node *head)函数上,但我不明白为什么。
在这段代码中,我必须接受用户输入并以链接列表的形式创建字典。这是完整的代码:
#include<stdio.h>
#include<stdlib.h>
#include<ctype.h>
#include<string.h>
//To count the number of times an element was added to the dictionary
static int countWords=0;
typedef struct node{
char string[255]; //store the data
struct node *next; //pointer to the next structure -> this is a pointer
}node;
//Prints the list
void printList(node *head){
node *p = head;
do{
for(int i=0; i<255; i++)
printf("%c", p->string[i]);
p = p -> next;
}
while(p->next != NULL);
}
//Inserts the word in alphabetical order in the list
node *insert_dictionary_order(char *pWord, node *dictionary){
node *head = dictionary; //head of the first node
node *temp = NULL; //Node that will be placed in the linked list
node *p = NULL; //iterator
//creating individual isolated nodes -> not attached to a list
temp = (node*)malloc(sizeof(node));
//This stores the values that pointer gives us in an array
char word[255];
for(int i=0; i<5; i++)
word[i] = *(pWord + i);
//instantiating the node member
temp->next = NULL;
for(int i=0; i<5; i++)
temp -> string[i] = word[i];
//LinkedList is still empty
if(head == NULL){
printf("\nWe get here4!!\n");
head = temp;
printList(head); //THIS DOESNT WORK
printf("\nWe get here5!!\n");
}
else{
printf("\nWe get here6!!\n");
p = head;
//Comparing temp to words in the dictionnary
//To know if we are at the first iteration (changing the head)
do{
printf("New word: %s\nDictionary Word: %s\n", temp -> string, p->string);
if(strcmp(temp->string, p->string) < 0 && countWords ==0){ //Special case for the head
temp -> next = p;
head = temp;
countWords++;
}
//Checking if we are at inserting position
else if(strcmp(temp->string, p->string) > 0 && strcmp(temp->string, (p->next)->string) < 0){
temp->next = p->next;
p->next = temp;
countWords++;
}
p = p->next;
}
while(p->next != NULL);
}
printList(head);
return head;
}
//To check if a certain character is a letter
int isALetter(char c){
if((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
c == '\0')
return 1;
else
return 0;
}
int main(){
node *dictionary = NULL;
//Prompting the user to enter strings
printf("Please enter some strings.\n");
//To store the strings that the user enters
char string[10000];
fgets(string, 10000, stdin);
//Putting the string to lower case for easy manipulations
for(int i=0; i<10000; i++)
string[i] = tolower(string[i]);
//To put the word in an array
char word[255];
//looping through the strings
int i=0;
//looping through the word
int j = 0;
//Checking the strings to put the words in the dictionnary
do{
//Checking if we need to escape the loop
if(i>0 && ((string[i] == '.' && string[i-1]== ' ' )|| string[i] == 0))
break;
//Checking if a letter
if(isALetter(string[i]) == 0){
i++;
continue;
}
//Checking if end of the word
if(isALetter(string[i+1]) == 0)
{
word[j] = string[i];
printf("\n");
char *pWord;
pWord = word;
printf("\nWe get here1!!\n");
//Adding word to the dictionary
dictionary = insert_dictionary_order(pWord, dictionary);
//***trying stuff
printf("\nWe get here2!!\n");
//***Printing the updated linked list
//printList(dictionary);
//***trying stuff
printf("\nWe get here3!!\n");
//reseting the word array
memset(word, 0, 255);
j = 0;
i++;
continue;
}
word[j] = string[i];
j++;
i++;
}
while(i != 10000);
//Printing the list
printf("\n\nPrinting the list..\n\n");
printList(dictionary);
return 0;
}
这是输出:
Please enter some strings.
zz aa
We get here1!!
We get here4!!
Segmentation fault (core dumped)
我们可以清楚地看到问题出在printList(node *head)带有此输出的方法上,因为“我们到这里了!” 数字2、3、5和6不会出现(它们全都在调用此方法之后)。
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请使用调试器。如果这样做,您会看到以下内容:
Please enter some strings.
aa zz
We get here1!!
We get here4!!
Program received signal SIGSEGV, Segmentation fault.
0x0000555555555334 in printList (head=0x612000000040) at t.c:26
26 while(p->next != NULL);
(gdb) p p
$1 = (node *) 0x0