From: Michael Welsh Duggan <md5i@md5i.com>
To: Jim Meyering <jim@meyering.net>
Cc: David Kastrup <dak@gnu.org>, emacs-devel@gnu.org
Subject: Re: oops? read/write vs type of length parameter
Date: Thu, 14 Apr 2011 16:57:43 -0400 [thread overview]
Message-ID: <87aafsh7p4.fsf@maru.md5i.com> (raw)
In-Reply-To: <87wrj0fo8x.fsf@rho.meyering.net> (Jim Meyering's message of "Mon, 11 Apr 2011 23:54:06 +0200")
Jim Meyering <jim@meyering.net> writes:
> David Kastrup wrote:
>> Jim Meyering <jim@meyering.net> writes:
>>
>>> What about when EMACS_INT is defined to "int"?
>>>
>>> Someone will inevitably call your write-like function
>>> with a length of type size_t -- many existing uses do just that --
>>> and by using a signed type, you will have converted their long
>>> yet valid (2-4GiB), buffer length, into a negative number.
>>
>> Resulting in an error or nothing happening. In contrast, if a negative
>> number is turned into a long yet valid (2-4GiB) number, it is very
>> likely that unintended memory areas will get stomped over.
>
> Since someone mentioned a goal of being able to edit a 2GiB
> file, I thought people here would be sensitive to an API policy
> that renders that goal unreachable on some systems.
>
> Of course the extra bit doesn't matter when you start with 64,
> but starting with only 32, using an unsigned "length" would
> avoid that unnecessary limit.
Forgive me if this is already known, but I believe the POSIX standard
says that "If the value of nbyte is greater than {SSIZE_MAX}, the result
is implementation-defined." This implies that there is no guarantee
that the extra bit would ever be reliably used anyway.
--
Michael Welsh Duggan
(md5i@md5i.com)
next prev parent reply other threads:[~2011-04-14 20:57 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-11 8:55 oops? read/write vs type of length parameter Jim Meyering
2011-04-11 9:44 ` Eli Zaretskii
2011-04-11 11:08 ` Jim Meyering
2011-04-11 11:28 ` David Kastrup
2011-04-11 11:52 ` Eli Zaretskii
2011-04-11 12:27 ` Jim Meyering
2011-04-11 12:31 ` David Kastrup
2011-04-11 21:54 ` Jim Meyering
2011-04-12 4:44 ` Eli Zaretskii
2011-04-12 13:24 ` Ted Zlatanov
2011-04-12 13:29 ` Eli Zaretskii
2011-04-12 14:47 ` Ted Zlatanov
2011-04-12 17:00 ` Large file support (was: oops? read/write vs type of length parameter) Eli Zaretskii
2011-04-14 20:57 ` Michael Welsh Duggan [this message]
2011-04-11 14:02 ` oops? read/write vs type of length parameter Eli Zaretskii
2011-04-11 11:40 ` Stephen J. Turnbull
2011-04-11 13:58 ` Eli Zaretskii
2011-04-12 1:16 ` Paul Eggert
2011-04-12 3:01 ` Eli Zaretskii
2011-04-12 5:06 ` Paul Eggert
2011-04-12 5:46 ` Eli Zaretskii
2011-04-12 8:19 ` Paul Eggert
2011-04-12 9:41 ` Eli Zaretskii
2011-04-12 15:53 ` Paul Eggert
2011-04-12 16:56 ` Eli Zaretskii
2011-04-12 23:55 ` Juanma Barranquero
2011-04-13 5:14 ` Paul Eggert
2011-04-13 6:31 ` Jim Meyering
2011-04-13 6:37 ` Eli Zaretskii
2011-04-13 8:15 ` Paul Eggert
2011-04-13 9:46 ` Eli Zaretskii
2011-04-13 16:06 ` Paul Eggert
2011-04-13 17:22 ` Eli Zaretskii
2011-04-13 19:31 ` Paul Eggert
2011-04-13 19:59 ` PJ Weisberg
2011-04-14 4:49 ` Eli Zaretskii
2011-04-13 20:02 ` Paul Eggert
2011-04-13 6:49 ` Eli Zaretskii
2011-04-13 14:35 ` Ted Zlatanov
2011-04-15 13:13 ` Ted Zlatanov
2011-04-15 16:34 ` Paul Eggert
2011-04-15 18:20 ` Ted Zlatanov
2011-04-15 1:29 ` Stefan Monnier
2011-04-15 8:55 ` Paul Eggert
2011-04-15 9:41 ` Eli Zaretskii
2011-04-15 10:24 ` Paul Eggert
2011-04-12 12:32 ` Davis Herring
2011-04-12 13:38 ` Eli Zaretskii
2011-04-12 15:43 ` Paul Eggert
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