我有2个结构:wires和wireLLN(wires的链表节点)。这个想法是,findWire() 函数在链表中查找具有与给定导线 (wireName) 相同名称的导线的节点。添加第一条连线时,不会出现任何问题,因为头节点为空,因此会创建一个新节点,并将该连线作为节点的“wire”属性。 addNode 中的 printf 调用显示了这一点。然而,在第二次运行 findWire() 时,尝试访问头节点的“wire”属性会导致段错误。 (我已经评论了代码中出现段错误的位置)
typedef struct wires {
bool value;
char* name;
} Wire;
typedef struct wireLLN {
Wire wire;
struct wireLLN * nextNode;
} WireLLN;
//head of the linked list
WireLLN * headWire = NULL;
// adds a node to the linked list
void addNode(WireLLN* head, WireLLN* node){
if (headWire == NULL){
headWire = node;
printf("Head node was null. Adding node with wire name: %s\n", headWire->wire.name); //this prints no problem
}
else if (head->nextNode == NULL)
head->nextNode = node;
else
addNode(head->nextNode, node);
}
//finds if a wire with a given name already exists, if not returns null
Wire * findWire(char wireName[], WireLLN * head){
if (headWire != NULL){
puts("head wasnt null");
printf("HEAD NODE ADDRESS: %s\n", head);
printf("HEAD WIRE: %s\n", head->wire); //SEG FAULT HERE
if (strcmp(head->wire.name, wireName) == 0){
puts("1");
return &head->wire;
} else if (head->nextNode == NULL){
puts("2");
return NULL;
} else {
puts("3");
return findWire(wireName, head->nextNode);
}
} else return NULL;
}
// assigns a wire to a gate if it exists, otherwise creates a new one then assigns it
Wire assignWire(char wireName[]){
Wire * result = findWire(wireName, headWire);
if (result == NULL){
Wire wire = makeWire(wireName);
WireLLN node;
node.wire = wire;
addNode(headWire, &node);
return wire;
} else {
return *result;
}
}
感谢您的宝贵时间。
最佳答案
您遇到内存释放问题。你忘记了,一旦该功能停止运行,你的内存就会被删除。 这发生在 allocateWireFunction 中。
您可能想将其更改为:
Wire assignWire(char wireName[]){
Wire * result = findWire(wireName, headWire);
if (result == NULL){
//to prevent the data being lost after the function returns
WireLLN* node = (WireLLN*)malloc(sizeof(WireLLN));
node->wire = makeWire(wireName);
addNode(headWire, node);
return node->wire;
} else {
return *result;
}
}
您的 NULL 检查之所以没有警告您,是因为一旦函数返回,您给 addNode 的指针就停止分配内存。 然后您访问该内存(地址相同),但它不是允许您写入任何内容的内存。
关于C - 赋值后访问结构体属性会导致段错误,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/49469185/