From: Alejandro Colomar <alx@kernel.org>
To: libc-alpha@sourceware.org, Eric Blake <eblake@redhat.com>
Cc: linux-man@vger.kernel.org
Subject: LINE_MAX
Date: Mon, 20 May 2024 23:49:13 +0200 [thread overview]
Message-ID: <qjp55g4oisyltajr4hckjgqjfbfwx7w5jwfgpeuqhdghppxrft@khoxlratj7kl> (raw)
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Hi Eric!
I think I found a bug in POSIX.1-2017 (and probably, previous ones too,
but didn't check).
<https://pubs.opengroup.org/onlinepubs/009695399/basedefs/limits.h.html>:
{LINE_MAX}
Unless otherwise noted, the maximum length, in bytes, of a
utility’s input line (either standard input or another
file), when the utility is described as processing text
files. The length includes room for the trailing <newline>.
Minimum Acceptable Value: {_POSIX2_LINE_MAX}
It doesn't say anything about the trailing null byte for the buffer that
holds it, but I assume it doesn't include it, from the context.
However:
<https://pubs.opengroup.org/onlinepubs/009695399/functions/fgets.html>:
The following sections are informative.
EXAMPLES
Reading Input
The following example uses fgets() to read each line of input. {LINE_MAX}, which defines the maximum size of the input line, is defined in the <limits.h> header.
#include <stdio.h>
...
char line[LINE_MAX];
...
while (fgets(line, LINE_MAX, fp) != NULL) {
...
}
...
This example seems to contradict my understanding of what limits.h says.
So, either limits.h should be explicit that the trailing null byte is
also included in LINE_MAX, or the example is bogus and should be fixed.
I guess it's the latter, although I wish it was the former, so we can
avoid a +1 in the code.
In any case, could you please forward this to the Austin group?
Have a lovely night!
Alex
--
<https://www.alejandro-colomar.es/>
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next reply other threads:[~2024-05-20 21:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-20 21:49 Alejandro Colomar [this message]
2024-05-20 22:26 ` LINE_MAX Vincent Lefevre
2024-05-21 10:08 ` LINE_MAX Alejandro Colomar
2024-05-21 11:40 ` LINE_MAX Vincent Lefevre
2024-05-20 22:35 ` LINE_MAX Lennart Jablonka
2024-05-21 10:14 ` LINE_MAX Alejandro Colomar
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