内存分配

遇到内存分配为NULL的问题

发布于 2022-04-28 21:14:36 浏览：489 订阅该版

在调试发布版4.1.0的时候，遇到问题：

调用RT_KERNEL_MALLOC
```c
object = (struct rt_object *)RT_KERNEL_MALLOC(information->object_size);
    if (object == RT_NULL)
    {
        /* no memory can be allocated */
        return RT_NULL;
    }
```
发现object为空，最后确定是_MEM_MALLOC(_size) 这个宏返回为空，source insight打开发现下面_MEM_MALLOC定义处的宏开关貌似都没有打开

```c
#if defined(RT_USING_SMALL_MEM_AS_HEAP)
static rt_smem_t system_heap;
rt_inline void _smem_info(rt_size_t *total,
    rt_size_t *used, rt_size_t *max_used)
{
    if (total)
        *total = system_heap->total;
    if (used)
        *used = system_heap->used;
    if (max_used)
        *max_used = system_heap->max;
}
#define _MEM_INIT(_name, _start, _size) \
    system_heap = rt_smem_init(_name, _start, _size)
#define _MEM_MALLOC(_size)  \
    rt_smem_alloc(system_heap, _size)
#define _MEM_REALLOC(_ptr, _newsize)\
    rt_smem_realloc(system_heap, _ptr, _newsize)
#define _MEM_FREE(_ptr) \
    rt_smem_free(_ptr)
#define _MEM_INFO(_total, _used, _max)  \
    _smem_info(_total, _used, _max)
#elif defined(RT_USING_MEMHEAP_AS_HEAP)
static struct rt_memheap system_heap;
void *_memheap_alloc(struct rt_memheap *heap, rt_size_t size);
void _memheap_free(void *rmem);
void *_memheap_realloc(struct rt_memheap *heap, void *rmem, rt_size_t newsize);
#define _MEM_INIT(_name, _start, _size) \
    rt_memheap_init(&system_heap, _name, _start, _size)
#define _MEM_MALLOC(_size)  \
    _memheap_alloc(&system_heap, _size)
#define _MEM_REALLOC(_ptr, _newsize)    \
    _memheap_realloc(&system_heap, _ptr, _newsize)
#define _MEM_FREE(_ptr)   \
    _memheap_free(_ptr)
#define _MEM_INFO(_total, _used, _max)   \
    rt_memheap_info(&system_heap, _total, _used, _max)
#elif defined(RT_USING_SLAB_AS_HEAP)
static rt_slab_t system_heap;
rt_inline void _slab_info(rt_size_t *total,
    rt_size_t *used, rt_size_t *max_used)
{
    if (total)
        *total = system_heap->total;
    if (used)
        *used = system_heap->used;
    if (max_used)
        *max_used = system_heap->max;
}
#define _MEM_INIT(_name, _start, _size) \
    system_heap = rt_slab_init(_name, _start, _size)
#define _MEM_MALLOC(_size)  \
    rt_slab_alloc(system_heap, _size)
#define _MEM_REALLOC(_ptr, _newsize)    \
    rt_slab_realloc(system_heap, _ptr, _newsize)
#define _MEM_FREE(_ptr) \
    rt_slab_free(system_heap, _ptr)
#define _MEM_INFO       _slab_info
#else
#define _MEM_INIT(...)
#define _MEM_MALLOC(...)     RT_NULL
#define _MEM_REALLOC(...)    RT_NULL
#define _MEM_FREE(...)
#define _MEM_INFO(...)
#endif
```

- RT_USING_SMALL_MEM_AS_HEAP
- RT_USING_MEMHEAP_AS_HEAP
- RT_USING_SLAB_AS_HEAP

应该是宏`#define _MEM_MALLOC(...)     RT_NULL`最终这样被定义为NULL的原因吧。
上面那几个宏在哪里定义，应该选哪个定义？