小内存管理法里面heap_mem 初始化问题

    heap_ptr = (rt_uint8_t *)begin_align;
    RT_DEBUG_LOG(RT_DEBUG_MEM, ("mem init, heap begin address 0x%x, size %d\n",
                                (rt_ubase_t)heap_ptr, mem_size_aligned));
    /* initialize the start of the heap */
    mem        = (struct heap_mem *)heap_ptr;
    mem->magic = HEAP_MAGIC;
    mem->next  = mem_size_aligned + SIZEOF_STRUCT_MEM;
    mem->prev  = 0;
    mem->used  = 0;

 mem->next  = mem_size_aligned + SIZEOF_STRUCT_MEM;

mem->next  = heap_ptr + mem_size_aligned + SIZEOF_STRUCT_MEM;