malloc返回地址的对齐问题

http://man7.org/linux/man-pages/man3/malloc.3.html

RETURN VALUE         top

       The malloc() and calloc() functions return a pointer to the allocated
       memory, which is suitably aligned for any built-in type.

因为占内存最多的变量类型为double和int64，都是8字节。

那么，malloc返回的地址都是8字节对齐的吗？

对于lwip的mem_alloc()也是都是8字节对齐吗？

https://stackoverflow.com/questions/8752546/how-does-malloc-understand-alignment