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From: "sgk at troutmask dot apl.washington.edu" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/107753] gfortran returns NaN in complex divisions
 (x+x*I)/(x+x*I) and (x+x*I)/(x-x*I)
Date: Sat, 19 Nov 2022 00:25:28 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107753

--- Comment #9 from Steve Kargl <sgk at troutmask dot apl.washington.edu> -=
--
On Fri, Nov 18, 2022 at 11:24:29PM +0000, sgk at troutmask dot
apl.washington.edu wrote:
>=20
> Does anyone know what is meant by "Fortran rules"?  F66 does not
> have any particular algorithm specified.  I'll look at F77 shortly.
>=20

Well, I hunted down the origins of -fcx-fortran-rules.

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D29549

So, it appears to be an optimization, where Smith's algorithm
will fail for extreme values of the real and imaginary parts
of the complex number.=