RE: [lwip-devel] recent 32-bit alignment patch in HEAD and requirementfor libc

[Mountifield, Tony]

Hi Leon,

> 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.

I agree, and should have thought of it before. I'm just testing a new patch
against today's CVS that will do this, change the use of memcmp() back to
ip_addr_cmp() and include a couple of other slight fixes I found were needed.
I'll post it to the existing bug #8708 shortly.

Cheers,
Tony


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