死机内存释放

5 free a bad data block导致机器死机问题咨询

发布于 2020-08-10 16:07:29 浏览：1638 订阅该版

4 个回答

liu2guang 认证专家 2020-08-12

This guy hasn't written anything yet

iamyhw 2020-08-12

This guy hasn't written anything yet

memtrace是一种办法,不过用起来不够直接,我介绍一个我经常用的办法,抛砖引玉,
下面以我调试rtgui为例说说怎么做的,
方法是直接改造malloc和free函数,先在头文件中,将malloc改成宏定义,

```c
#define TRACE_MEM

#ifdef TRACE_MEM
void* trace_rmalloc(rt_size_t n, const char *f, int line);
void* trace_realloc(void *ptr, rt_size_t size, const char *f, int line);
void trace_free(void *ptr, const char *f, int line);
struct mem_trace
{
    rt_list_t   list;
    rt_uint32_t total_alloc;
    rt_uint32_t total_realloc;
    rt_uint32_t total_free;
};
enum { MALLOC = 0, REALLOC = 1 };
struct mem_node
{
    rt_uint32_t *addr;
    rt_uint32_t len;
	rt_uint8_t  *f;
	rt_uint32_t line;
	rt_uint16_t type;
    rt_list_t   list;
};
#define rtgui_malloc(n)     trace_malloc(n, __FUNCTION__, __LINE__)
#define rtgui_realloc(p, n) trace_realloc(p, n, __FUNCTION__, __LINE__)
#define rtgui_free(p)       trace_free(p, __FUNCTION__, __LINE__)
#else
#define rtgui_malloc(n)     rt_malloc(n)
#define rtgui_realloc(p, n) rt_realloc(p, n)
#define rtgui_free(p)       rt_free(p)
#endif

#endif
然后改造malloc,free:

#ifdef TRACE_MEM
struct mem_trace trace_mm;
void trace_init(void)
{
    trace_mm.total_alloc = 0;
    trace_mm.total_realloc = 0;
    trace_mm.total_free = 0;
    rtgui_list_init(&trace_mm.list);
}

void *trace_malloc(rt_size_t n, const char *f, int line)
{
    void *p = NULL;
	//rt_kprintf("malloc %s()\n", f);
    p = malloc(n);
    if (p) {
        struct mem_node *m = rt_malloc(sizeof(struct mem_node));
        m->addr = p; 
        m->len = n;
		m->f = f;
		m->line = line;
		m->type = MALLOC;

rtgui_list_append(&trace_mm.list, &m->list);
        trace_mm.total_alloc += n; 
    }

return p;
}

void *trace_realloc(void *ptr, rt_size_t size, const char *f, int line)
{
	struct mem_node *m;
    void *p = NULL;
    p = realloc(ptr, size);

rtgui_list_t *node;
	rtgui_list_foreach(node, &trace_mm.list)
	{
		m = rtgui_list_entry(node, struct mem_node, list);
		if (m->addr == ptr) {
			trace_mm.total_alloc -= m->len;
			trace_mm.total_alloc += size;
			m->addr = p;
			m->len = size;
			m->f = f;
			m->line = line;
			m->type = REALLOC;
			break;
		}
	}

return p;
}

void trace_free(void *ptr, const char *f, int line)
{
    struct mem_node *m;
    rtgui_list_t *node;
    rtgui_list_foreach(node, &trace_mm.list)
    {
		m = rtgui_list_entry(node, struct mem_node, list);
        if (m->addr == ptr) {
            trace_mm.total_alloc -= m->len;
			rtgui_list_remove(&trace_mm.list, &m->list);
            break;
        }
    }

free(ptr);
}

void trace_list(void) {
	struct mem_node *m;
	rtgui_list_t *node;
	if (trace_mm.list.next != RT_NULL) {
		rt_kprintf("This memory may not have been freed: \n");
		rtgui_list_foreach(node, &trace_mm.list)
		{
			m = rtgui_list_entry(node, struct mem_node, list);
			trace_mm.total_alloc -= m->len;
			rtgui_list_remove(&trace_mm.list, &m->list);
			rt_kprintf("%8s 0x%08x, %s()%d, [%d bytes]\n", (m->type==0) ? "malloc" : "realloc", m->addr, m->f, m->line, m->len);

rtgui_list_remove(&trace_mm.list, &m->list);
		}
	}
}

#endif
```

应用时,
在程序最开始的地方调用:
trace_init();
在程序最后结束的地方调用:
trace_list();
这样就可以将泄漏的内存统统抓出来,
正常释放的在free中就移除了,剩下的都是未释放的.
缺点是trace本身也会占用一部分内存,解除泄漏后及时关闭它.