Re: PDP-10 backend for gcc

[Michael Meissner <meissner at cygnus dot com>]

On Wed, Sep 06, 2000 at 11:18:00AM +0200, lars brinkhoff wrote:
> Andrew Morton <andrewm@uow.edu.au> writes:
> > Michael Meissner wrote:
> > > Given this byte pointer-ness has been in the compiler
> > > since its inception, I suspect you will find
> > > undocumented assumptions rife throughout the compiler.
> > 
> > You suspect correctly.  I once ported gcc/g++ 2.5.8 to a
> > bit-addressable machine.  A machine where you have to add
> > 8 to an address register to advance it by a byte.
> > 
> > I found thirty or forty instances of this byte == 1
> > assumption, and basically the only way of tracking
> > them down was working backwards from incorrect
> > code generation.
> 
> Isn't it about time gcc was enhanced to support "weird" pointers?

Sure I do.  FYI, since I wrote a (non GCC) C compiler front end for a machine
with weird pointers (Data General MV/Eclipse, RIP) and supported it for 5
years, I can certainly agree that it is needed.  However, I tend to have much
more on my plate than I can code....

I'm just warning you that it is a big job.  Even after you are done, be
prepapred to find that a lot of net code will fail due to many C programmers
being unable to figure out that logically each different type of pointer can
potentially have a different size or layout, other than the char * == void *,
and all struct/union pointers must have the same size and layout requirements
that are in the C standards.

-- 
Michael Meissner, Red Hat, Inc.
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