Subject: printf(3) manpage: please document that %n can't include flags,
width or precision
Date: Thu, 31 Jul 2014 11:27:26 +0200
Package: manpages-dev
Version: 3.65-1
Severity: minor
The only place where flags for the n conversion are mentioned in
description of the 0 flag:
Except for n conversions, ...
This is a bit odd, because the other flags don't make sense for %n
either. In fact, the C99 standard says that if the n conversion
specification includes any flags, a field width, or a precision, the
behavior is undefined.
Please document this fact in the manual page.
--
Jakub Wilk
Subject: Re: Bug#756602: printf(3) manpage: please document that %n can't
include flags, width or precision
Date: Thu, 31 Jul 2014 12:42:25 +0200
tags 756602 fixed-upstream
thanks
Hello Jakub,
I've applied the patch below.
Cheers,
Michael
--- a/man3/printf.3
+++ b/man3/printf.3
@@ -332,9 +332,7 @@ For other conversions, the behavior is undefined.
.B \-
The converted value is to be left adjusted on the field boundary.
(The default is right justification.)
-Except for
-.B n
-conversions, the converted value is padded on the right with blanks, rather
+The converted value is padded on the right with blanks, rather
than on the left with blanks or zeros.
A
.B \-
@@ -788,10 +786,17 @@ or
.TP
.B n
The number of characters written so far is stored into the integer
-indicated by the
-.I "int\ *"
-(or variant) pointer argument.
+pointed to by the corresponding argument.
+That argument shall be an
+.I "int\ *",
+or variant, as specified by the
+.B l
+or
+.B ll
+length modifier.
No argument is converted.
+The behavior is undefined if the conversion specification includes
+any flags, a field width, or a precision.
.TP
.B m
(Glibc extension.)
Subject: Re: Bug#756602: printf(3) manpage: please document that %n can't
include flags, width or precision
Date: Thu, 31 Jul 2014 18:41:24 +0200
* Michael Kerrisk <[email protected]>, 2014-07-31, 12:42:
>I've applied the patch below.
Thanks!
>+That argument shall be an
>+.I "int\ *",
>+or variant, as specified by the
>+.B l
>+or
>+.B ll
>+length modifier.
Hmm. Why only l or ll?
According to the C99 standard, all the length modifiers that can be used
with integer conversions (hh, h, l, ll, j, z, t) can be also used with
%n.
--
Jakub Wilk
Subject: Re: Bug#756602: printf(3) manpage: please document that %n can't
include flags, width or precision
Date: Fri, 1 Aug 2014 08:55:19 +0200
On Thu, Jul 31, 2014 at 6:41 PM, Jakub Wilk <[email protected]> wrote:
> * Michael Kerrisk <[email protected]>, 2014-07-31, 12:42:
>
>> I've applied the patch below.
>
>
> Thanks!
>
>
>> +That argument shall be an
>> +.I "int\ *",
>> +or variant, as specified by the
>> +.B l
>> +or
>> +.B ll
>> +length modifier.
>
>
> Hmm. Why only l or ll?
>
> According to the C99 standard, all the length modifiers that can be used
> with integer conversions (hh, h, l, ll, j, z, t) can be also used with %n.
>
> --
> Jakub Wilk
Good point. How about:
[[
That argument shall be an
.I "int\ *",
or variant whose size matches the (optionally)
supplied integer length modifier.
]]
?
Cheers,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
Subject: Re: Bug#756602: printf(3) manpage: please document that %n can't
include flags, width or precision
Date: Fri, 1 Aug 2014 12:46:08 +0200
* Michael Kerrisk <[email protected]>, 2014-08-01, 08:55:
>[[
>That argument shall be an
>.I "int\ *",
>or variant whose size matches the (optionally)
>supplied integer length modifier.
>]]
Looks good to me, thanks!
Now I noticed that in the "The length modifier" subsection, the n
conversion is mentioned only in the descriptions of hh, h, l, and ll.
Could we make it more consistent?
--
Jakub Wilk
Subject: Re: Bug#756602: printf(3) manpage: please document that %n can't
include flags, width or precision
Date: Fri, 1 Aug 2014 15:08:06 +0200
On Fri, Aug 1, 2014 at 12:46 PM, Jakub Wilk <[email protected]> wrote:
> * Michael Kerrisk <[email protected]>, 2014-08-01, 08:55:
>
>> [[
>> That argument shall be an
>> .I "int\ *",
>> or variant whose size matches the (optionally)
>> supplied integer length modifier.
>> ]]
>
>
> Looks good to me, thanks!
>
> Now I noticed that in the "The length modifier" subsection, the n conversion
> is mentioned only in the descriptions of hh, h, l, and ll. Could we make it
> more consistent?
I applied the below.
Thanks,
Michael
diff --git a/man3/printf.3 b/man3/printf.3
index 47fdf2c..47fa149 100644
--- a/man3/printf.3
+++ b/man3/printf.3
@@ -527,6 +527,10 @@ A following integer conversion corresponds to an
.I intmax_t
or
.I uintmax_t
+argument, or a following
+.B n
+conversion corresponds to a pointer to an
+.I intmax_t
argument.
.TP
.B z
@@ -534,6 +538,10 @@ A following integer conversion corresponds to a
.I size_t
or
.I ssize_t
+argument, or a following
+.B n
+conversion corresponds to a pointer to a
+.I size_t
argument.
.\" (Linux libc5 has
.\" .B Z
@@ -543,6 +551,10 @@ argument.
.B t
A following integer conversion corresponds to a
.I ptrdiff_t
+argument, or a following
+.B n
+conversion corresponds to a pointer to a
+.I ptrdiff_t
argument.
.PP
SUSv2 knows about only the length modifiers
Source: manpages
Source-Version: 3.71-1
We believe that the bug you reported is fixed in the latest version of
manpages, which is due to be installed in the Debian FTP archive.
A summary of the changes between this version and the previous one is
attached.
Thank you for reporting the bug, which will now be closed. If you
have further comments please address them to [email protected],
and the maintainer will reopen the bug report if appropriate.
Debian distribution maintenance software
pp.
Simon Paillard <[email protected]> (supplier of updated manpages package)
(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing [email protected])
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
Format: 1.8
Date: Thu, 21 Aug 2014 23:05:57 +0200
Source: manpages
Binary: manpages manpages-dev
Architecture: source all
Version: 3.71-1
Distribution: unstable
Urgency: medium
Maintainer: Martin Schulze <[email protected]>
Changed-By: Simon Paillard <[email protected]>
Description:
manpages - Manual pages about using a GNU/Linux system
manpages-dev - Manual pages about using GNU/Linux for development
Closes: 708394728240729436745775746569748887754514756602
Changes:
manpages (3.71-1) unstable; urgency=medium
.
* Imported Upstream version 3.71 (Closes: #754514)
. getrusage.2: _GNU_SOURCE must be defined to obtain RUSAGE_THREAD
definition (Closes: #746569)
. strcasecmp.3: Explain why defined in both <string.h>
and <strings.h> (Closes: #729436)
. stat.2: Describe feature test macro requirements for file type test
macro (Closes: #728240)
. connect.2: ERRORS: Add EADDRNOTAVAIL for ephemeral port range exhaustion
(Closes: #745775)
. stdio.3: typo fix (Closes: #748887)
. connect.2: ERRORS: add EPROTOTYPE (Closes: #708394)
. printf.3: details of the %n conversion specifier (Closes: #756602)
. new manpages:
fanotify.7 fanotify_init.2 fanotify_mark.2 group_member.3
iconv.1 iconvconfig.8 isfdtype.3 localedef.1 procfs.5 renameat2.2
repertoiremap.5 sched.7 sched_getattr.2 sched_setattr.2 sched_setattr.2
sprof.1
* d/control: Take over iconv.1 localedef.1 iconvconfig.8 from libc-bin,
and sprof.1 from libc-dev-bin
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