From: Achim Gratz <Stromeko@nexgo.de>
To: cygwin@cygwin.com
Subject: Re: gcc 11.1.0: printf("%.43f\n", 0x1.52f8a8e32e982p-140): printed value is incorrectly rounded
Date: Sun, 13 Jun 2021 11:42:38 +0200 [thread overview]
Message-ID: <87o8caumlt.fsf@Rainer.invalid> (raw)
In-Reply-To: <CAL9Mx1uMOz2wfqbMpD_xfA=D9JkpFzVz6AR_DKHK34AvrGOP6w@mail.gmail.com> (Pavel M. via Cygwin's message of "Sat, 12 Jun 2021 23:45:54 +0300")
Pavel M via Cygwin writes:
> Sample code (t903.c):
> #include <stdio.h>
> int main(void)
> {
> printf("%.43f\n", 0x1.52f8a8e32e982p-140);
> return 0;
> }
>
> Invocations:
> # gcc on Windows 10 (Cygwin)
> $ gcc t903.c -Wall -Wextra -std=c11 -pedantic -Wfatal-errors && ./a.exe
> 0.0000000000000000000000000000000000000000010
You will want to report this against newlib, I'd think. If I remember
correctly, newlib uses a single guard digit for the conversion and for
such an algorithm the result you see is expected and correct. Whether
any later C standard would mandate to use an algorithm that uses higher
precision (in terms of guard digits you'd end up with 15 for your
example before you get the expected result I think) I have no idea.
Regards,
Achim.
--
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+
SD adaptation for Waldorf rackAttack V1.04R1:
http://Synth.Stromeko.net/Downloads.html#WaldorfSDada
next prev parent reply other threads:[~2021-06-13 9:42 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-12 20:45 Pavel M
2021-06-13 9:42 ` Achim Gratz [this message]
2021-06-13 19:19 ` Brian Inglis
2021-11-03 21:07 ` Pavel M
2021-11-03 21:09 ` Pavel M
[not found] ` <CAL9Mx1utCxXFPy3vOK0ZOkX2qzt8ntQ0LEyD4WvLpCRRbTLYeQ@mail.gmail.com>
2021-11-03 21:32 ` Pavel M
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