Bug#388852: libc6: csqrt(): non-principal root on -i (per upstream)

[Kevin Ryde <user42@zip.com.au>]

Package: libc6
Version: 2.3.6.ds1-4
Severity: normal
Tags: patch

When given a negative imaginary number, csqrt() returns a negative
real part, whereas the principal root should be the one with positive
real part.  Sample program below.

I believe this was fixed upstream last year.  It'd be nice to have the
same in debian.

    http://sources.redhat.com/cgi-bin/cvsweb.cgi/libc/sysdeps/generic/Attic/s_csqrt.c.diff?r1=1.2&r2=1.3&cvsroot=glibc&hideattic=0

(The s_csqrt.c file moved to under /math, hence this diff being from
the attic.)


-- System Information:
Debian Release: testing/unstable
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: i386 (i586)
Shell:  /bin/sh linked to /bin/dash
Kernel: Linux 2.6.15-1-486
Locale: LANG=en_AU, LC_CTYPE=en_AU (charmap=ISO-8859-1)

Versions of packages libc6 depends on:
ii  tzdata                        2006l-1    Time Zone and Daylight Saving Time

libc6 recommends no packages.

-- no debconf information

#include <complex.h>
#include <stdio.h>

volatile complex double z = - _Complex_I;

int
main (void)
{
  z = csqrt (z);
  printf ("re=%g im=%g\n", creal (z), cimag (z));
  return 0;
}