[英]C EXC_BAD_ACCESS Crash in Linked List
I am building a linked list in C which stores strings and allows you to search the linked list to see if an element exists. 我正在C中建立一个链表,该链表存储字符串,并允许您搜索链表以查看元素是否存在。 For some reason, every 2-3 times that I run the following code with a linked list containing around 6,000 elements, I get an EXC_BAD_ACCESS
error on the following line: 出于某种原因,我每隔2-3次运行以下代码并使用包含约6,000个元素的EXC_BAD_ACCESS
,就会在以下行中收到EXC_BAD_ACCESS
错误:
if (strcmp(list->value, value) == 0) return true;
This EXC_BAD_ACCESS
error is due to it accessing list->value. 这个EXC_BAD_ACCESS
错误是由于它访问list-> value。 I don't understand why this could be since I never have a string larger than my LINE_BUFFER
and I allocate my memory on to the heap before setting the value pointer. 我不明白为什么会这样,因为我从来没有一个大于LINE_BUFFER
的字符串,并且在设置值指针之前我将内存分配给了堆。 That means that that memory should never be deallocated, correct? 这意味着内存永远都不会被释放,对吗?
My line buffer declaration: 我的行缓冲区声明:
#define LINE_BUFFER 81
Here's the linked list Node
struct: 这是链接列表Node
结构:
struct Node {
struct Node *next;
char *value;
};
typedef struct Node Node;
Here's the linked list code: 这是链接列表代码:
Node * create_node(Node *list, char *value) {
Node *node = malloc(sizeof(Node));
node->value = strcpy(malloc(sizeof(char) * LINE_BUFFER), value); // make sure value is on the heap
// find the end of the list
Node *end = NULL;
while (list) {
end = list;
list = list->next;
}
// add this node to the end if necessary
if (end) {
end->next = node;
}
return node;
}
Node * init_list(char *value) {
Node *node = create_node(NULL, value);
return node;
}
Node * add_list(Node *list, char *value) {
Node *node = create_node(list, value);
return node;
}
bool search_list(Node *list, char *value) {
while (list) {
if (strcmp(list->value, value) == 0) return true;
list = list->next;
}
return false;
}
void free_list(Node *list) {
if (!list) return;
Node *next = list->next;
free(list->value);
free(list);
free_list(next);
}
It appears that you never initialize node->next
to NULL
in create_node
. 看来您永远不会在create_node
中将node->next
初始化为NULL
。 So walking the list will dereference uninitialized memory, and eventually crash when it contains invalid pointers. 因此,遍历该列表将取消引用未初始化的内存,并最终在包含无效指针时崩溃。
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