[Bug libc/16623] New: cos change of behavior in 2.19 causes scipy testfailures

["jtaylor.debian at googlemail dot com" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=16623

            Bug ID: 16623
           Summary: cos change of behavior in 2.19 causes scipy
                    testfailures
           Product: glibc
           Version: 2.19
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: jtaylor.debian at googlemail dot com
                CC: drepper.fsp at gmail dot com

#include <math.h>
#include <stdio.h>
int main()
{
  double x= 4831921577.4601803;
  printf("%.15g\n", sin(x));
  printf("%.15g\n", cos(x));
}


in glibc 2.18:

gcc test.c -lm && ./a.out 
-0.918193578775631
-0.396131987972694

while 2.19 has the sign of the cosinus has changed:
gcc test.c -lm && ./a.out 
-0.918193578775631
0.396131987972694

I can't judge if that is within the allowed accuracy of libc but it is causing
wrong results in funpack used for special functions in python-scipy.

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