Re: How to stop gcc padding structs???

[Grant Edwards <grante at visi dot com>]

> > > > > Relying on sizeof to do this is *very* non-portable.
> > > > 
> > > > It's a device driver for a specific board.  It doesn't really
> > > > need to be portable.
> > > 
> > > The fact that it is a device driver for a specific board means that
> > > you're not going to try to port it to a different board.  But
> > > well-written device drivers do get ported to different operating
> > > systems, or compiled with different compilers.  For example, one
> > > reason why you might want to port to a different compiler is that you
> > > might discover that the compiler you're using is buggy.  Note that
> > > even upgrading to a later version of the same compiler may expose you
> > > to some of the same portability issues.
> > 
> > True.  I suppose for maximum portability I should just use
> > pointer arithmatic with hard-wired offsets.  It's just so ugly.
> 
> Which of course will not work so well if your device is put into a non-x86 or
> non-ppc that traps when given an unaligned pointer (ie, a normal RISC
> machine).

If the board is redesigned with a different processor, then the
bus-interface logic that hooks up to the peripheral chip would
have to change.

I wasn't aware of any popular processors that had alignment
requirements for chars.  The variables I'm trying to get mapped
to specific addresses are chars.

-- 
Grant Edwards
grante@visi.com