Segmentation Fault 11，C

Question

我一直試圖在C中實現一個LinkedList以實際實現我在C中學到的理論。我一直得到一個Segmentation fault: 11.任何有關如何解決這個問題的幫助將不勝感激。這裏是我的代碼：

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

struct Element { 
    int value; 
    struct Element *nextElement; 
}; 

struct LinkedList { 
    struct Element *firstElement; 
}; 

void add(struct LinkedList *list, int value) { 
    if(list->firstElement == NULL) { 
     struct Element *newElement; 
     newElement = malloc(sizeof(struct Element)); 

     newElement->value = value; 

     list->firstElement = newElement; 
    } else { 
     struct Element *lastElement; 

     lastElement = list->firstElement; 

     while(lastElement->nextElement != NULL) { 
      lastElement = lastElement->nextElement; 
     } 

     struct Element *newElement; 
     newElement = malloc(sizeof(struct Element)); 

     newElement->value = value; 

     lastElement->nextElement = newElement; 
    } 
} 

void showAllElements(struct LinkedList *list) { 
    struct Element *lastElement = list->firstElement; 

    while(lastElement != NULL) { 
     printf("%d\n", lastElement->value); 
     lastElement = lastElement->nextElement; 
    } 
} 

int main() 
{ 
    struct LinkedList list; 
    add(&list, 5); 
    add(&list, 10); 
    add(&list, 15); 
    showAllElements(&list); 

    return 0; 
} 

Answer 1

所以，你的代碼有幾個問題。 struct LinkedList list未分配。當你做list->firstElement時它會出錯。與

struct LinkedList list = {NULL}

而且newElement初始化它不會給nextElement。您還需要將其設置爲NULL，否則在訪問時會出錯。

struct Element *newElement; 
    newElement = malloc(sizeof(struct Element)); 

    newElement->value = value; 
    newElement->nextElement = NULL;