我正在尝试在数组中执行循环缓冲区。我将数据保存在结构中,并通过push,pop等方法来管理它。该程序或多或少具有功能并且行为与预期相同,但是我在valgrind测试中遇到了错误。而且我无法找出我的代码出了什么问题。虽然看起来像通过指针在我的结构中管理数据是至关重要的问题。如果有人能指出我正确的方向,我会非常感激,因为我现在真的迷失了。从结构“无效读/写”中的指针获取数据
这是我的结构看起来像:
typedef struct queue_t{
int* data;
int* end;
int* head;
int* tail;
int max_length;
int cur_length;
} queue_t;
这里是我的方法来管理缓冲区操作:
(注释代码产生几乎同样的错误作为的memcpy)
int* increase(int* point, queue_t* queue){
if(point != queue->end){
point = point + sizeof(int*);
return point;
}else{
return queue->data;
}
}
queue_t* create_queue(int capacity){
queue_t* fifo;
fifo = malloc(sizeof(queue_t));
fifo->data = malloc((capacity) * sizeof(int*));
fifo->end = fifo->data + (capacity*sizeof(int*));
fifo->head = fifo->data;
fifo->tail = fifo->data;
fifo->cur_length = 0;
fifo->max_length = capacity;
return fifo;
}
void delete_queue(queue_t *queue){
free(queue->data);
free(queue);
}
bool push_to_queue(queue_t *queue, void *data){
int *temp = (int*) data;
//*(queue->tail) = *temp;
memcpy(queue->tail, temp, sizeof(int));
free(data);
if(queue->max_length != queue->cur_length){
queue->cur_length++;
}
queue->tail = increase(queue->tail, queue);
if(queue->tail == queue->head){
queue->head = increase(queue->head, queue);
}
return true;
}
void* pop_from_queue(queue_t *queue){
if(queue->cur_length == 0){
return NULL;
}
int *item = malloc(sizeof(int*));
//*item = *(queue->head);
memcpy(item, queue->head, sizeof(int));
queue->head = increase(queue->head, queue);
queue->cur_length--;
return item;
}
这是我测试提到的缓冲区操作的功能性的主要方法:
(queue.h是我的功能而定义的)
#include "queue.h"
void print_int(void* p){
if(p != NULL){
printf("%d\n", *((int*)p));
} else {
printf("NULL\n");
}
}
int main(){
int n = 2;
int max = 10;
queue_t *q;
q = create_queue(n);
for(int i = 0; i<max;i++){
int* p = malloc(sizeof(int));
*p = i;
if(!push_to_queue(q, (void*)p)){
free(p);
exit(101);
}
}
for(int i = 0;i<max;i++){
void* p = pop_from_queue(q);
print_int(p);
free(p);
}
delete_queue(q);
return 0;
}
最后,这是我的valgrind输出:代码
==20293== HEAP SUMMARY:
==20293== in use at exit: 0 bytes in 0 blocks
==20293== total heap usage: 15 allocs, 15 frees, 1,136 bytes allocated
==20293==
==20293== All heap blocks were freed -- no leaks are possible
==20293==
==20293== ERROR SUMMARY: 7 errors from 2 contexts (suppressed: 0 from 0)
==20293==
==20293== 1 errors in context 1 of 2:
==20293== Invalid read of size 4
==20293== at 0x40097C: pop_from_queue (queue.c:72)
==20293== by 0x400713: main (main.c:30)
==20293== Address 0x52030f0 is 16 bytes before a block of size 4 free'd
==20293== at 0x4C2EDEB: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==20293== by 0x4008B8: push_to_queue (queue.c:51)
==20293== by 0x4006D5: main (main.c:23)
==20293== Block was alloc'd at
==20293== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==20293== by 0x4006B5: main (main.c:21)
==20293==
==20293==
==20293== 6 errors in context 2 of 2:
==20293== Invalid write of size 4
==20293== at 0x4008AB: push_to_queue (queue.c:50)
==20293== by 0x4006D5: main (main.c:23)
==20293== Address 0x52030d0 is 16 bytes after a block of size 16 alloc'd
==20293== at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==20293== by 0x4007FB: create_queue (queue.c:33)
==20293== by 0x40069E: main (main.c:18)
==20293==
==20293== ERROR SUMMARY: 7 errors from 2 contexts (suppressed: 0 from 0)
尖线有:
72: memcpy(item, queue->head, sizeof(int));
50: memcpy(queue->tail, temp, sizeof(int));
非常感谢,我希望有人能够告诉我,我在这里做的那个坏习惯是什么:/
也许不是根本原因,但仍然会出现在我眼前:这个int * item = malloc(sizeof(int *));'没有任何意义。 'item'指向一个'int',所以它指向的字节数应该是int的大小,而不是int *的大小。所以你想仔细检查指针,如何分配给它们以及它们最终复制到它们指向的内容。 – alk
非常感谢,纠正了,但错误仍然存在......我也会在其他分配中检查这个 – shade254