DMARC-Filter: OpenDMARC Filter v1.4.2 delorie.com 4B9BmgPT796447
Authentication-Results: delorie.com; dmarc=pass (p=none dis=none) header.from=cygwin.com
Authentication-Results: delorie.com; spf=pass smtp.mailfrom=cygwin.com
DKIM-Filter: OpenDKIM Filter v2.11.0 delorie.com 4B9BmgPT796447
Authentication-Results: delorie.com;
	dkim=pass (1024-bit key, unprotected) header.d=cygwin.com header.i=@cygwin.com header.a=rsa-sha256 header.s=default header.b=vpGErSoR
X-Recipient: archive-cygwin AT delorie DOT com
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org D00313858416
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1733744921;
	bh=SRWtsy9DycHTd0nj7DHLpWqvZ9CdYmvWdaQkNKIIgnU=;
	h=Date:To:Subject:References:In-Reply-To:List-Id:List-Unsubscribe:
	 List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc:
	 From;
	b=vpGErSoRHQEAHC1QiRFry6fPzw0BkHcJNaLZEntzrS6vDBswnxFASt3l936JVy2nf
	 PSbo8BC1MnieyCQmwq5FIvaKKJrVDZJgEZheCJEms4oyd4dZ6PvxGAu4qO0OkTrilB
	 XTX2DCrGVTuxiPTqNAdKHh2ztoqCsM2iE4aqDOIg=
X-Original-To: cygwin AT cygwin DOT com
Delivered-To: cygwin AT cygwin DOT com
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org DA0133858CDB
Date: Mon, 9 Dec 2024 12:48:14 +0100
To: cygwin AT cygwin DOT com
Subject: Re: Bug in handling of "1$", "2$" in printf format
Message-ID: <Z1bY_pHnT4TTdKCb@calimero.vinschen.de>
Mail-Followup-To: cygwin AT cygwin DOT com
References: <CAAHpriPTSi-ji2xqX_yhNbtkdX_BxBr=tzchN=Gxk4dXg3kbAw AT mail DOT gmail DOT com>
 <295c1185-c839-40df-80a7-2a59a4d742ca AT dronecode DOT org DOT uk>
MIME-Version: 1.0
Content-Disposition: inline
In-Reply-To: <295c1185-c839-40df-80a7-2a59a4d742ca@dronecode.org.uk>
X-BeenThere: cygwin AT cygwin DOT com
X-Mailman-Version: 2.1.30
Precedence: list
List-Id: General Cygwin discussions and problem reports <cygwin.cygwin.com>
List-Unsubscribe: <https://cygwin.com/mailman/options/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=unsubscribe>
List-Archive: <https://cygwin.com/pipermail/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-request AT cygwin DOT com?subject=help>
List-Subscribe: <https://cygwin.com/mailman/listinfo/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=subscribe>
From: Corinna Vinschen via Cygwin <cygwin AT cygwin DOT com>
Reply-To: cygwin AT cygwin DOT com
Cc: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Errors-To: cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com
Sender: "Cygwin" <cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com>

On Dec  7 16:33, Jon Turney via Cygwin wrote:
> On 07/12/2024 05:26, Keith Thompson via Cygwin wrote:
> > Brian Inglis wrote:
> > > On 2024-12-06 19:16, Keith Thompson via Cygwin wrote:
> > > > The use of "1$", "2$" et al in printf format specifiers is a
> > > > POSIX-specific feature.
> > > > 
> > > > On Cygwin (newlib) this is handled correctly in most cases, but one
> > > > example I tried misbehaves.
> > > > The output is correct on other implementations, including glibc and
> > > > musl on Ubuntu.
> > > > 
> > > > This C program:
> > > > 
> > > > #include <stdio.h>
> > > > int main(void) {
> > > >       long long a = 123456789876543210;
> > > >       double b=1.0/3;
> > > >       printf("a:%2$8.8lld b:%1$10.2g\n", b, a);
> > > > }
> > > > 
> > > > should produce this output:
> > > > 
> > > > a:123456789876543210 b:      0.33
> > > > 
> > > > Under Cygwin (fully updated), with "gcc c.c -o c && ./c", the output is:
> > > > 
> > > > a:140732550844138 b:  7.1e-315
> > > > 
> > > 
> > > Confirmed with gcc 12.4 and minor tweaks to constant data types: printf is
> > > ignoring arg positions:
> > [SNIP]
> > 
> > It's not always ignoring arg positions. I think there's an interaction
> > between the "1$" / "2$" position specification and relatively complex
> > format specifiers.  The following case works correctly:
> > 
> > $ cat c2.c
> > #include <stdio.h>
> > int main(void) {
> >      int a = 42;
> >      double b = 1.0/3.0;
> >      printf("a:%2$d b:%1$g\n", b, a);
> >      printf("a:%1$d b:%2$g\n", a, b);
> >      printf("a:%d b:%g\n",     a, b);
> > }
> > $ gcc c2.c -o c2 && ./c2
> > a:42 b:0.333333
> > a:42 b:0.333333
> > a:42 b:0.333333
> > $
> > 
> > (And the version of gcc shouldn't matter.  printf is implemented in
> > newlib.  The code in question should be in newlib/libc/stdio/vfprintf.c.)
> 
> Not sure if this is the same/similar/different to the problem I reported at
> [1]
> 
> [1] https://sourceware.org/pipermail/newlib/2023/020374.html

Yeah, we might need a patch there...

Corinna

-- 
Problem reports:      https://cygwin.com/problems.html
FAQ:                  https://cygwin.com/faq/
Documentation:        https://cygwin.com/docs.html
Unsubscribe info:     https://cygwin.com/ml/#unsubscribe-simple