better code
Posted Jun 2, 2003 6:13 UTC (Mon) by
eru (subscriber, #2753)
In reply to:
better code by tjc
Parent article:
strlcpy()
>> Pointer comparison is undefined if the pointers are not within the same
>> object, so this is not portable standard C.
>
> I've heard of this, but I have never read a good explanation. I just
> assumed that this restiction has something to do with pointer aliasing. If
> you understand this, now is the time to show off! ;-)
I always assumed the restriction in the C standard exists mainly because
in segmented memory management, the numeric values of pointers do not
necessarily correspond to their relative arrangement in memory.
Comparison is meaningful only for pointers that have the same segment
part. Since Linux does not use segmentation, at least not in an
user-visible way, there is no need to worry about this. (Few operating
systems use segments these days, but I happen to work with one that does,
even though it runs on the 32-bit versions of x86. Yes, 48-bit pointers!)
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