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Date: Thu, 03 Jun 2021 13:25:07 +0200
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From: Paul Zimmermann <Paul.Zimmermann@inria.fr>
To: Marco Atzeri <marco.atzeri@gmail.com>
Cc: newlib@sourceware.org
In-Reply-To: <2f8796f4-f164-5734-16ca-9a392e788beb@gmail.com> (message from
 Marco Atzeri on Wed, 2 Jun 2021 21:07:45 +0200)
Subject: Re: incorrectly rounded square root
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       Dear Marco,

> current Cygwin produces for both i686 and X86_64
> 
>   $ gcc -DNEWLIB -fno-builtin test_sqrt.c  -lm
> 
>   $ ./a.exe
> RNDN: 0x1.ff83fp+63
> RNDZ: 0x1.ff83fp+63
> RNDU: 0x1.ff83fp+63
> RNDD: 0x1.ff83fp+63

make sure you are using the Newlib fenv.h (or print the values of FE_TONEAREST,
FE_TOWARDZERO, FE_UPWARD, FE_DOWNWARD). Cf my previous mail.

Paul