Question

我的程序因与无效堆指针相关的错误而崩溃。在第一个函数中，我分配5个单元格并用“snake_head”指向列表中的第一个元素，“snake_tail”指向最后一个元素。在第二个函数中，我尝试从列表中释放最后一个元素，并将snake_tail移动到列表中的下一个单元格。解冻snake_tail时出了点问题。我不明白它是什么。

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

typedef struct pos_s {
    unsigned int x;
    unsigned int y;
}pos_t;


typedef struct snake_cell_s {
    pos_t pos;
    struct snake_cell_s* next;
    //    struct snake_cell_s* prev;
} snake_cell_t;



void init_snake(snake_cell_t** snake_head, snake_cell_t** snake_tail)
{
    int i;
    const int init_snake_size = 5;
    unsigned int init_snake_x = 5;
    unsigned int init_snake_y = 5;

    *snake_head = (snake_cell_t*)malloc(sizeof(snake_cell_t)*init_snake_size);
    snake_cell_t* snake_cell[init_snake_size];

    for (i = 0; i<init_snake_size; ++i) {
        snake_cell[i] = (*snake_head) + i;
        snake_cell[i]->pos.x = init_snake_x + i;
        snake_cell[i]->pos.y = init_snake_y;

        if (i<init_snake_size - 1) {
            snake_cell[i]->next = *snake_head + i + 1;
        }
        else {
            snake_cell[i]->next = NULL;
        }
    }
    *snake_tail = snake_cell[init_snake_size - 1];
    (*snake_tail)->next = NULL;
}




snake_cell_t* advance_snake_tail(snake_cell_t* snake_head, snake_cell_t* snake_tail)
{
    snake_cell_t* snake_new_tail;
    snake_cell_t* snake_cell = snake_head;

    while (snake_cell->next->next != NULL)
    {
        snake_cell = snake_cell->next;
    }

    snake_new_tail = snake_cell;
    snake_new_tail->next = NULL;
    free(snake_tail);      //  < ----   crash happens here
    return snake_new_tail;
}







int main()
{
    snake_cell_t* snake_head = NULL;
    snake_cell_t* snake_tail = NULL;
    init_snake(&snake_head, &snake_tail);     // create a 5 cell snake list
    snake_tail = advance_snake_tail(snake_head, snake_tail); // update snake tail- remove last cell and move pointer to previous cell
    return 0;
}

Answer 1

您{{}} free malloc未返回的指针。 - immibis

尝试释放链接列表的元素时出现CrtIsValidHeapPointer错误

1 个答案: