Re: [lwip-devel] recent 32-bit alignment patch in HEAD and requirement for libc

[Leon Woestenberg]

Hello,

Atte Kojo wrote:

> On Thu, 2004-04-29 at 02:14, Leon Woestenberg wrote:
>
> > reviewing some lwIP code, I noticed that the new 32-bit alignment
> > patch (now in HEAD) relies on a standard C library function:
> >
> >     if (!memcmp(ipaddr, &arp_table[i].ipaddr, sizeof(struct ip_addr))) {
> >
> > As far as I know, lwIP did not require the C library before.
> >
> > Can other developers confirm this? If true, we may need to remove this
> > requirement again.
>
>
> There is a macro called ip_addr_cmp() in ip_addr.h. I think it should be
> used instead of memcmp().
Yes, it used that function before. It was replaced by a memcmp() as 
ip_addr_cmp() operates on pointers to 32-bit IP address values which 
will not work if the address is unaligned.

So, we either need to change ip_addr_cmp() or make sure that what it
gets are aligned values.

I would choose for the second approach using a temporary variable.

Regards,

Leon.