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To: cygwin AT cygwin DOT com
Subject: Re: sqrtl behavior inconsistent with sqrt and sqrtf
Date: Tue, 27 Oct 2020 07:44:32 -0400
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References: <vriulffr2a1e DOT fsf AT mail DOT aol DOT com>
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From: airplanemath via Cygwin <cygwin AT cygwin DOT com>
Reply-To: airplanemath <airplanemath AT aol DOT com>
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airplanemath via Cygwin <cygwin AT cygwin DOT com> writes:

> Compiling and running the attached program with the command line below
> produces the output below:
>
> $ gcc -O0 -Og test_sqrt.c -o test_sqrt && ./test_sqrt
> Long double: -inf -inf
> Double:      -inf -nan
> Float:       -inf -nan
>
> I suspect the behavior for long double should be the same as for double
> and float (sqrt(-inf) = nan), but I'm not sure where to change that.
> I'm running a snapshot of Cygwin 3.2.0, if that's important.

The mail archive says I'm bad at attaching things.
Program source included below:

#include <math.h>
#include <stdio.h>

int main() {
  long double a, b;
  double c, d;
  float f, g;
  a = (long double) -INFINITY;
  c = (double) -INFINITY;
  f = (float) -INFINITY;
  b = sqrtl(a);
  d = sqrt(c);
  g = sqrtf(f);
  printf("Long double: %4Lf %4Lf\n", a, b);
  printf("Double:      %4lf %4lf\n", c, d);
  printf("Float:       %4f %4f\n", f, g);
  return 0;
}

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