sizeof, ptrs, lint, portability

[Kevin Martin]

In article <8121 at brl-tgr.ARPA> cottrell at nbs-vms.ARPA writes:
>-) I apologize for calling (presumably someone's favorite) machines `weird'
>   or `braindamaged'. Let's say `less capable'.
Let's say 'capable of doing things other than you want done'.
I doubt that a pianist would like being called 'weird', 'braindamaged',
or even 'less capable' just because you happen to want to hear her play a
trombone.

>   Allowing any other value to actually be stored breaks this. Besides,
>   SHOW ME A C THAT USES ANYTHING OTHER THAN ZERO ON ANY MACHINE!!!
>   K&R says of pointer to integer conversions: "The mapping funxion is
>   also machine dependent, but is intended to be unsurprising to those
>   who know the machine." I would be surprised at nonzero null ptrs.
Then you obviously don't know the machine.
A Honeywell DPS8, running CP-6, uses the bit pattern 06014 (36 bits)
as the null pointer (byte offset zero in segment number 014).
The pointer to int casts (and back) are accomplished by ex-oring
with this value.
The value 0 CAN'T be used, since this is a valid pointer.

>-) How many of you port what percentage of programs? I thought the
>   intent of the standard was to not break existing programs.
I don't think it does break programs (except those which use =<op>
and initializers without the '='). Your programs will continue
to run on systems on which they previously ran. You may get
more warnings when you compile them, though.

                     Kevin Martin, UofW Software Development Group