From: Markus Wichmann <nullplan@gmx.net>
To: musl@lists.openwall.com
Subject: Re: [musl] Minor style patch to exit.c
Date: Sun, 19 Jan 2020 15:24:01 +0100 [thread overview]
Message-ID: <20200119142401.GG2020@voyager> (raw)
In-Reply-To: <8299f261-7870-57a6-37cf-d4ce482ad81e@openwall.com>
On Sun, Jan 19, 2020 at 04:33:47PM +0300, Alexander Cherepanov wrote:
> Couldn't _start defined as an array? Then separate values could be accessed
> simply as elements of this array. And casts to integers could be limited to
> calculating the number of elements, the terminating value or something.
>
That reminds me of something I read in the C standard: Two pointers must
compare equal if, among other possibilities, one is a pointer to
one-past its underlying array, and the other is a pointer to the start
of its array, and the arrays happen to lie behind one another in address
space.
Therefore, if _start and _end were arrays, even the GCC devs must agree
that there might be an integer i such that _start + i == _end. For the C
language, _start and _end would be arrays that happen to lie adjacent in
address space.
And if we have guarantees from the outside attesting to that, then
_end - _start is no longer an undefined expression, right?
Ciao,
Markus
next prev parent reply other threads:[~2020-01-19 14:24 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-19 11:07 Markus Wichmann
2020-01-19 11:12 ` Markus Wichmann
2020-01-19 11:31 ` Szabolcs Nagy
2020-01-19 12:17 ` Markus Wichmann
2020-01-19 13:33 ` Alexander Cherepanov
2020-01-19 14:24 ` Markus Wichmann [this message]
2020-01-19 14:49 ` Pascal Cuoq
2020-01-19 15:53 ` Alexander Cherepanov
2020-01-19 16:22 ` Rich Felker
2020-01-19 21:02 ` Alexander Cherepanov
2020-01-19 14:46 ` Alexander Monakov
2020-01-19 16:18 ` Rich Felker
2020-01-19 17:11 ` Alexander Monakov
2020-01-19 17:17 ` Alexander Monakov
2020-01-19 17:19 ` Rich Felker
2020-01-19 17:32 ` Alexander Monakov
2020-01-19 17:38 ` Rich Felker
2020-01-19 19:13 ` Alexander Monakov
2020-01-19 16:33 ` Alexander Cherepanov
2020-01-19 16:39 ` Rich Felker
2020-01-19 21:34 ` Alexander Cherepanov
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