RE: [lwip-users] alignment problems

[Pettinato, Jim]

I've never seen a compiler that supported 8 bit chars that couldn't
address each of them individually. The processor may not address them
individually, but you should be able to access each char independently
at the higher level. That's what higher level languages do - hide the
details of the hardware.

Access to individual char values on a word-based bus may result in the
compiler generating a read+shift or read+mask, but you still can
typically load/store even and odd addressed characters at the 'C' level.


-----Original Message-----
From: address@hidden
[mailto:address@hidden On Behalf
Of Kieran Mansley
Sent: Thursday, November 08, 2007 6:27 AM
To: Mailing list for lwIP users
Subject: Re: [lwip-users] alignment problems

On Thu, 2007-11-08 at 11:08 +0000, Jonathan Larmour wrote:

> I'm concerned that you say that "two addresses" are only used with 
> long, and one for both char and int. Does this mean that for:
> char foo[4];
> that: &foo[0] == &foo[1] ?
> 
> If that is the case, I think you may have an uphill struggle.

Yeah, that confused me.  Sounds like it would be sensible to think of it
as having 16-bit bytes rather than worrying about the word size.  If
that's the case I think there may be problems for you in lwIP where
we've confused bytes with octets (i.e. 8 bits).

Kieran



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