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Date: Mon, 31 Jul 2023 18:41:06 +0900
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Subject: Re: Probable bug
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From: Takashi Yano via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
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On Sun, 30 Jul 2023 20:37:35 +0900
Takashi Yano wrote:
> On Sun, 30 Jul 2023 07:29:10 -0400
> Eliot Moss wrote:
> > On 7/30/2023 5:38 AM, natan_b--- via Cygwin wrote:
> > > Hi Guys
> > > 
> > > very short.
> > > 
> > > prog.c
> > > 
> > > #include <stdio.h>
> > >   
> > > int main()
> > > {
> > > float a=1.283;
> > > while(1)
> > > printf( "%f", a );
> > > }
> > >   
> > > run with
> > > $ ./prog.exe >/dev/null
> > >   
> > > in windows monitor process the process increase it's memory it arrive to many  Gb.
> > > It's not a machine problem, other PC have same problem.
> > >   
> > > Same program in wsl and MSYS2 works well!
> > 
> > This probably has to do with output buffering, and may happen even without
> > the >/dev/null since there are no line ends in the output.  It may work with
> > stdbuf -o0 (as in: stdbuf -o0 ./prog.exe >/dev/null) but may cause the program
> > to run more slowly (each character is sent to the device, when then immediately
> > discards it).  It would seem you're hoping for the internal libraries to
> > recognize the case of writing to /dev/null ...
> 
> I also suspected that, however, it was not correct.
> 
> while (1) sprintf(buf, "%f\n", a);
> 
> has the same problem. :-(

I looked into this problem, and found the cause.
This is the serious bug in the commit:

commit a4705d387f7874f9a5de3ee67861773a17691643
Author: Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
Date:   Wed Dec 1 06:11:32 2021 +0900

    ldtoa: Import gdtoa from OpenBSD.

    - This patch uses gdtoa imported from OpenBSD if newlib configure
      option "--enable-newlib-use-gdtoa=no" is NOT specified.  gdtoa
      provides more accurate output and faster conversion than legacy
      ldtoa, while it requires more heap memory.

Please let me consider how to fix that.

-- 
Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>

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