From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: possible snprintf() regression in 3.3.2
Date: Wed, 17 Nov 2021 13:27:55 +0100 [thread overview]
Message-ID: <YZT1S8wDnaBuYf5u@calimero.vinschen.de> (raw)
In-Reply-To: <20211117182108.b38599f5e13071bf269a0d48@nifty.ne.jp>
On Nov 17 18:21, Takashi Yano via Cygwin wrote:
> On Wed, 17 Nov 2021 11:37:18 +1100
> Tony Cook wrote:
> > This came up from regression testing perl.
> >
> > Regression testing of perl @4a1b9dd524007193213d3919d6a331109608b90c
> > used (from uname):
> > [...]
> I found the caused by the commit:
> commit 4d90e5335914551862831de3e02f6c102b78435b
> Author: Corinna Vinschen <corinna@vinschen.de>
> Date: Thu Nov 4 11:30:44 2021 +0100
>
> ldtoa: fix dropping too many digits from output
>
> ldtoa cuts the number of digits it returns based on a computation of
> number of supported bits (144) divide by log10(2). Not only is the
> integer approximation of log10(2) ~= 8/27 missing a digit here, it
> also fails to take really small double and long double values into
> account.
>
> Allow for the full potential precision of long double values. At the
> same time, change the local string array allocation to request only as
> much bytes as necessary to support the caller-requested number of
> digits, to keep the stack size low on small targets.
>
> In the long run a better fix would be to switch to gdtoa, as the BSD
> variants, as well as Mingw64 do.
>
> Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
>
> Reverting this commit solves the problem.
>
> Corinna, could you please have a look?
I don't have a good solution. The old ldtoa code is lacking, for
switching newlib to gdtoa I simply don't have the time. On the newlib
list was a short discussion starting at
https://sourceware.org/pipermail/newlib/2021/018626.html but nothing
came out of it yet.
Patches gratefully accepted (except just reverting the above change).
Corinna
next prev parent reply other threads:[~2021-11-17 12:27 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-17 0:37 Tony Cook
2021-11-17 9:21 ` Takashi Yano
2021-11-17 12:27 ` Corinna Vinschen [this message]
2021-11-18 0:06 ` Tony Cook
2021-11-18 11:35 ` Takashi Yano
2021-11-18 13:19 ` Corinna Vinschen
2021-11-18 14:11 ` Noel Grandin
2021-11-18 14:27 ` Corinna Vinschen
2021-11-18 21:08 ` Sam Edge
2021-11-21 0:16 ` Tony Cook
2021-11-22 10:34 ` Corinna Vinschen
2021-11-22 13:04 ` Corinna Vinschen
2021-11-22 23:23 ` Tony Cook
2021-11-23 8:34 ` Takashi Yano
2021-11-23 9:48 ` Corinna Vinschen
2021-11-24 3:40 ` Takashi Yano
2021-11-24 8:48 ` Corinna Vinschen
2021-11-24 8:52 ` Takashi Yano
2021-11-24 9:14 ` Takashi Yano
2021-11-24 9:28 ` Corinna Vinschen
2021-11-24 12:29 ` Lemke, Michael SF/HZA-ZI2E
2021-11-25 12:02 ` Takashi Yano
2021-11-25 12:45 ` Corinna Vinschen
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