malloc的突然失效 [英] malloc fails catastrophically
问题描述
我想实现一个队列C.从Java和其它托管语言的到来,我真的内存管理挣扎。这里是排队()
功能:
I am trying to implement a Queue in C. Coming from Java and other managed languages, I am really struggling with memory management. Here is the enqueue()
function:
int enqueue(Queue q, int value) {
Node newNode = malloc(sizeof(Node));
/*newNode->value = value;
if (q->size == 0)
q->head = newNode;
else
q->head->next = &newNode;
q->size++;*/
}
我得到这个错误:
I am getting this error :
malloc.c:3096: sYSMALLOc: Assertion `(old_top == (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) >= (unsigned long)((((__builtin_offsetof (struct malloc_chunk, fd_nextsize))+((2 * (sizeof(size_t))) - 1)) & ~((2 * (sizeof(size_t))) - 1))) && ((old_top)->size & 0x1) && ((unsigned long)old_end & pagemask) == 0)' failed.
FWIW,这里的code的其余部分(这是甚至对不对?):
FWIW, here's the rest of the code (is this even right?):
typedef struct NodeStruct *Node;
struct NodeStruct {
Node* prev;
Node* next;
int value;
};
typedef struct QueueStruct *Queue;
struct QueueStruct {
Node* head;
Node* tail;
int size;
int capacity;
};
Queue newQueue(int size) {
Queue q = malloc(sizeof(Queue));
q->capacity = size;
q->size = 0;
q->head = NULL;
q->tail = NULL;
return q;
}
void printQueue(Queue q) {
printf("Queue of size %d, capacity %d", q->size, q->capacity);
}
int main() {
Queue myQ = newQueue(10);
// this seems to work
printQueue(myQ);
// epic fail
enqueue(myQ, 5);
return 0;
}
为什么会出现这种情况?
Why is this happening?
推荐答案
下面的行可能给你的悲伤:
The following line is probably giving you grief:
Node newNode = malloc(sizeof(Node));
节点
为指针类型,所以你只分配足够的空间容纳一个指针,而不是一个完整的 NodeStruct
。我想你想要做的是:
Node
is a pointer type, so you're only allocating enough space to hold a pointer, not an entire NodeStruct
. I think what you want to do is:
Node newNode = malloc(sizeof(*newNode));
或
Node newNode = malloc(sizeof(NodeStruct));
存在同样的问题队列
,你只分配了空间容纳一个指针,而不是一个 QueueStruct
。别的,我只是刚刚注意到,就是在你的 NodeStruct
和 QueueStruct
,您使用的类型节点*
,这实际上是 NodeStruct **
,这可能不是你想要的,因为节点
已经是一个指针。
The same issue exists for Queue
, you're only allocated space to hold a pointer, not a QueueStruct
. Something else that I only just noticed, is that in your NodeStruct
and QueueStruct
, you are using the type Node*
, which is actually NodeStruct **
, which is probably not what you want, since Node
is already a pointer.
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