[Bug libstdc++/43802] New: Tanh Returns Incorrect Value

["tomdean at speakeasy dot org" <gcc-bugzilla at gcc dot gnu dot org>]

In c and c++, tanh<complex> returns a different incorrect value.

test-tanh.c:  gcc test-tanh.c -o test-tanh-c-lm
test-tanh.cc: g++ test-tanh.cc -o test-tanh-cc
./test-tanh-c 711
libc version 2.10.1
libc release stable
arg        = 7.110000e+02 + 7.110000e+02 * i
sinh (arg) = inf + inf * i
cosh (arg) = inf + inf * i
s/c         = nan + nan * i   (should be 1 + 0 * i)
tanh (arg) = 0.000000e+00 + 0.000000e+00 * i   (should be 1 + 0 * i)

./test-tanh-cc 711
libc version 2.10.1
arg       (711,711)
sinh(arg) (1.64037e+308,2.55507e+308)
cosh(arg) (1.64037e+308,2.55507e+308)
s/c       (1,0)
tanh(arg) (1,4.93127e-618)

==== test-tanh.c ============================
#include <math.h>
#include <complex.h>
#include <stdio.h>
#define _GNU_SOURCE
#include <gnu/libc-version.h>

int main (int argc, char **argv)
{
  long double complex arg = 1 + _Complex_I;
  long double complex s, c, r, t;
  long mult;
  if (argc == 2) {
        mult = atol(argv[1]);
  } else {
        mult = 50000L;
  }

  arg *= mult;

  s = csinh (arg);
  c = ccosh (arg);
  r = s / c;
  t = ctanh (arg);

  printf ("libc version %s\n", gnu_get_libc_version ());
  printf ("libc release %s\n", gnu_get_libc_release ());
  printf ("arg        = %e + %e * i\n", creal (arg), cimag
                  (arg));
  printf ("sinh (arg) = %e + %e * i\n",
                  creal (s), cimag (s));
  printf ("cosh (arg) = %e + %e * i\n",
                  creal (c), cimag (c));
  printf("s/c         = %e + %e * i   (should be 1 + 0 * i)\n",
                 creal (r), cimag (r));
  printf ("tanh (arg) = %e + %e * i   (should be 1 + 0 * i)\n",
                  creal (t), cimag (t));
  return 0;
}

==== test-tanh.c ============================
#include <iostream>
#include <complex>
#include <gnu/libc-version.h>
#include <stdlib.h> // atol

using namespace std;

int main(int argc, char **argv) {
  long mult;
  if (argc == 2) {
        mult = atol(argv[1]);
  } else {
        mult = 50000L;
  }
  complex<long double> arg(1,1);

  arg *= mult;

  complex<long double> s,c,r,t;

  s=sinh(arg);
  c=cosh(arg);
  r=s/c;
  t=tanh(arg);

  cout << "libc version " << gnu_get_libc_version() << endl;
  cout << "arg       " << arg << endl;
  cout << "sinh(arg) " << s << endl;
  cout << "cosh(arg) " << c << endl;
  cout << "s/c       " << r << endl;
  cout << "tanh(arg) " << t << endl;

  return 0;
}


-- 
           Summary: Tanh Returns Incorrect Value
           Product: gcc
           Version: 4.4.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tomdean at speakeasy dot org
 GCC build triplet: Ubuntu 9.10 Distribution
  GCC host triplet: ubuntu 9.10
GCC target triplet: i686


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43802