GNU bug report logs - #13555
printf ignores length modifier

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: "Marcel Böhme" <hawkie <at> web.de>
To: bug-coreutils <at> gnu.org
Subject: printf ignores length modifier
Date: Sat, 26 Jan 2013 10:41:59 +0100 (CET)

Dear all,

I've been looking into the semantic changes introduced to printf with the commit 62e1d5259df82155ae52201678093381a35d898e (08.07.2004) and found besides a lot of progression (conformance to C99 etc.) the following oddities:

The tool printf ignores length modifiers (cf. http://linux.die.net/man/3/printf)
In fact, any (combination of) length modifier is substituted by "ll" as length modifier. Is this intended?

$old/printf "%hi\n" 0xFFFF
-1
$printf "%hi\n" 0xFFFF
65535

$old/printf  "%hi\n" 0xFFF
4095
$old/printf  "%hhLljtzllhi\n" 0xFFF
printf: %h: invalid directive
$printf  "%hhLljtzllhi\n" 0xFFF
4095


On the on hand the comment reads:
 332   /* Create a null-terminated copy of the % directive, with an
 333      intmax_t-wide length modifier substituted for any existing
 334      integer length modifier.  */

On the other hand the commit comment reads:
> Add support for C99 'j', 't', 'z' length modifiers (like Bash).

Best regards,
 Marcel


PS: http://git.savannah.gnu.org/gitweb/?p=coreutils.git;a=commitdiff;h=62e1d5259df82155ae52201678093381a35d898e

Message #8 received at 13555 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Marcel Böhme <hawkie <at> web.de>
Cc: 13555 <at> debbugs.gnu.org
Subject: Re: bug#13555: printf ignores length modifier
Date: Sat, 26 Jan 2013 08:37:42 -0800

On 01/26/2013 01:41 AM, Marcel Böhme wrote:
> $old/printf "%hi\n" 0xFFFF
> -1
> $printf "%hi\n" 0xFFFF
> 65535

None of these length modifiers are specified by POSIX,
so we're talking about what it's more useful for printf
to do, rather than whether this is a violation of
a standard.  coreutils printf should agree
with Bash printf, and Bash printf ignores the modifiers,
so if we change coreutils we should change Bash too.

I suppose that 'printf' could change its behavior, and
use (say) 32-bit int for '%li' on a x86 but 64-bit int
on x86-64, thus exposing the native machine widths to
the user.  However, for shell scripts I expect that more
people prefer portability to exposing the machine widths,
so the current behavior is better.

Message #11 received at 13555 <at> debbugs.gnu.org (full text, mbox):

From: Marcel Boehme <hawkie <at> web.de>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: "13555 <at> debbugs.gnu.org" <13555 <at> debbugs.gnu.org>
Subject: Re: bug#13555: printf ignores length modifier
Date: Sun, 27 Jan 2013 08:55:26 +0800

Dear Paul,

Then, I suppose, the observed semantic change for the mentioned version pair was _intended_. Found it odd that I didn't find documented that / why length modifiers are 'suddenly' ignored.

Thanks for your follow-up!

Best regards,
Marcel



On 27 Jan, 2013, at 12:37 AM, Paul Eggert <eggert <at> cs.ucla.edu> wrote:

> On 01/26/2013 01:41 AM, Marcel Böhme wrote:
>> $old/printf "%hi\n" 0xFFFF
>> -1
>> $printf "%hi\n" 0xFFFF
>> 65535
> 
> None of these length modifiers are specified by POSIX,
> so we're talking about what it's more useful for printf
> to do, rather than whether this is a violation of
> a standard.  coreutils printf should agree
> with Bash printf, and Bash printf ignores the modifiers,
> so if we change coreutils we should change Bash too.
> 
> I suppose that 'printf' could change its behavior, and
> use (say) 32-bit int for '%li' on a x86 but 64-bit int
> on x86-64, thus exposing the native machine widths to
> the user.  However, for shell scripts I expect that more
> people prefer portability to exposing the machine widths,
> so the current behavior is better.
> 

Message #14 received at 13555 <at> debbugs.gnu.org (full text, mbox):

From: Assaf Gordon <assafgordon <at> gmail.com>
To: Marcel Boehme <hawkie <at> web.de>, Paul Eggert <eggert <at> cs.ucla.edu>
Cc: "13555 <at> debbugs.gnu.org" <13555 <at> debbugs.gnu.org>
Subject: Re: bug#13555: printf ignores length modifier
Date: Thu, 18 Oct 2018 17:28:34 -0600

tags 13555 notabug
close 13555
stop

(triaging old bugs)

Hello,

> Paul Eggert <eggert <at> cs.ucla.edu> wrote:
>
>>  Marcel Böhme wrote:
>>> $old/printf "%hi\n" 0xFFFF
>>> -1
>>> $printf "%hi\n" 0xFFFF
>>> 65535
>>
>> None of these length modifiers are specified by POSIX,
>> so we're talking about what it's more useful for printf
>> to do, rather than whether this is a violation of
>> a standard.

On 26/01/13 05:55 PM, Marcel Boehme wrote:
> Then, I suppose, the observed semantic change for the mentioned version pair was _intended_. Found it odd that I didn't find documented that / why length modifiers are 'suddenly' ignored.
> 
> Thanks for your follow-up!

With no further comments in 5 years, I'm closing this bug.

-assaf

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