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Date: Sat, 29 Jun 2013 16:56:42 +0200
From: Jens Gustedt <jens.gustedt@...ia.fr>
To: musl@...ts.openwall.com
Subject: Re: Use of size_t and ssize_t in mseek
Am Samstag, den 29.06.2013, 10:17 -0400 schrieb Rich Felker:
> Just that this is one of a multitude of places that such a check could
> be made, and I question the value of doing it in one place but not
> others. Examples include snprintf, strnlen, memchr, and basically any
> interface that takes a size_t representing the size of an already
> existing object. I'm against adding checks to all these places since
> it adds bloat and potentially hurts performance and for most of them
> there's nothing they could do except crash if the check failed. So
> what I'm questioning is the value of adding such a check to the one
> interface you ran into trouble with, when there are plenty more widely
> used functions that won't be checked; this inconsistency does not make
> sense to me. I'd like to hear what others think, though.
I think C11 has indentified this sort of specification problems and
therefore introduces rsize_t and RSIZE_MAX in the not-loved-by-many
appendix K "bounds-checking intefaces". Interfaces that are specified
with this type are required to check that the value isn't too large
for any object.
If you'd want to go that road (of checking for the size) I'd suggest
that you'd define and use RSIZE_MAX for such a thing, and maybe even
change the interfaces to use rsize_t. Since this is only a typedef
such a change should still be compatible with size_t as in the current
and future standard(s), and it would clearly mark the intent of bounds
checking.
Jens
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