From 865c17fb28f8c3275fd94da6ee4ac51472ec874a Mon Sep 17 00:00:00 2001
From: Benjamin Peterson <benjamin@python.org>
Date: Wed, 12 Sep 2018 06:51:18 -0700
Subject: closes bpo-34640: Remove the TANH_PRESERVES_ZERO_SIGN configure
 check. (GH-9206)

---
 Lib/test/test_cmath.py |  2 --
 Lib/test/test_math.py  |  2 --
 configure              | 47 -----------------------------------------------
 configure.ac           | 27 ---------------------------
 pyconfig.h.in          |  3 ---
 5 files changed, 81 deletions(-)

diff --git a/Lib/test/test_cmath.py b/Lib/test/test_cmath.py
index 0451fb0..43a074b 100644
--- a/Lib/test/test_cmath.py
+++ b/Lib/test/test_cmath.py
@@ -577,8 +577,6 @@ class CMathTests(unittest.TestCase):
         self.assertTrue(cmath.isinf(complex(INF, NAN)))
 
     @requires_IEEE_754
-    @unittest.skipIf(sysconfig.get_config_var('TANH_PRESERVES_ZERO_SIGN') == 0,
-                     "system tanh() function doesn't copy the sign")
     def testTanhSign(self):
         for z in complex_zeros:
             self.assertComplexIdentical(cmath.tanh(z), z)
diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py
index 608789f..9b2f55e 100644
--- a/Lib/test/test_math.py
+++ b/Lib/test/test_math.py
@@ -1355,8 +1355,6 @@ class MathTests(unittest.TestCase):
         self.assertTrue(math.isnan(math.tanh(NAN)))
 
     @requires_IEEE_754
-    @unittest.skipIf(sysconfig.get_config_var('TANH_PRESERVES_ZERO_SIGN') == 0,
-                     "system tanh() function doesn't copy the sign")
     def testTanhSign(self):
         # check that tanh(-0.) == -0. on IEEE 754 systems
         self.assertEqual(math.tanh(-0.), -0.)
diff --git a/configure b/configure
index 9520446..fe642c4 100755
--- a/configure
+++ b/configure
@@ -14163,53 +14163,6 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF
 
 
-# On FreeBSD 6.2, it appears that tanh(-0.) returns 0. instead of
-# -0. on some architectures.
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether tanh preserves the sign of zero" >&5
-$as_echo_n "checking whether tanh preserves the sign of zero... " >&6; }
-if ${ac_cv_tanh_preserves_zero_sign+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-
-if test "$cross_compiling" = yes; then :
-  ac_cv_tanh_preserves_zero_sign=no
-else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-
-#include <math.h>
-#include <stdlib.h>
-int main() {
-    /* return 0 if either negative zeros don't exist
-       on this platform or if negative zeros exist
-       and tanh(-0.) == -0. */
-  if (atan2(0., -1.) == atan2(-0., -1.) ||
-      atan2(tanh(-0.), -1.) == atan2(-0., -1.)) exit(0);
-  else exit(1);
-}
-
-_ACEOF
-if ac_fn_c_try_run "$LINENO"; then :
-  ac_cv_tanh_preserves_zero_sign=yes
-else
-  ac_cv_tanh_preserves_zero_sign=no
-fi
-rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
-  conftest.$ac_objext conftest.beam conftest.$ac_ext
-fi
-
-fi
-
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_tanh_preserves_zero_sign" >&5
-$as_echo "$ac_cv_tanh_preserves_zero_sign" >&6; }
-if test "$ac_cv_tanh_preserves_zero_sign" = yes
-then
-
-$as_echo "#define TANH_PRESERVES_ZERO_SIGN 1" >>confdefs.h
-
-fi
-LIBS=$LIBS_SAVE
-
 # For multiprocessing module, check that sem_open
 # actually works.  For FreeBSD versions <= 7.2,
 # the kernel module that provides POSIX semaphores
diff --git a/configure.ac b/configure.ac
index 4b34bad..a985ec2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4359,33 +4359,6 @@ AC_CHECK_FUNCS([acosh asinh atanh copysign erf erfc expm1 finite gamma])
 AC_CHECK_FUNCS([hypot lgamma log1p log2 round tgamma])
 AC_CHECK_DECLS([isinf, isnan, isfinite], [], [], [[#include <math.h>]])
 
-# On FreeBSD 6.2, it appears that tanh(-0.) returns 0. instead of
-# -0. on some architectures.
-AC_MSG_CHECKING(whether tanh preserves the sign of zero)
-AC_CACHE_VAL(ac_cv_tanh_preserves_zero_sign, [
-AC_RUN_IFELSE([AC_LANG_SOURCE([[
-#include <math.h>
-#include <stdlib.h>
-int main() {
-    /* return 0 if either negative zeros don't exist
-       on this platform or if negative zeros exist
-       and tanh(-0.) == -0. */
-  if (atan2(0., -1.) == atan2(-0., -1.) ||
-      atan2(tanh(-0.), -1.) == atan2(-0., -1.)) exit(0);
-  else exit(1);
-}
-]])],
-[ac_cv_tanh_preserves_zero_sign=yes],
-[ac_cv_tanh_preserves_zero_sign=no],
-[ac_cv_tanh_preserves_zero_sign=no])])
-AC_MSG_RESULT($ac_cv_tanh_preserves_zero_sign)
-if test "$ac_cv_tanh_preserves_zero_sign" = yes
-then
-  AC_DEFINE(TANH_PRESERVES_ZERO_SIGN, 1,
-  [Define if tanh(-0.) is -0., or if platform doesn't have signed zeros])
-fi
-LIBS=$LIBS_SAVE
-
 # For multiprocessing module, check that sem_open
 # actually works.  For FreeBSD versions <= 7.2,
 # the kernel module that provides POSIX semaphores
diff --git a/pyconfig.h.in b/pyconfig.h.in
index 51e9213..360f799 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -1419,9 +1419,6 @@
    (which you can't on SCO ODT 3.0). */
 #undef SYS_SELECT_WITH_SYS_TIME
 
-/* Define if tanh(-0.) is -0., or if platform doesn't have signed zeros */
-#undef TANH_PRESERVES_ZERO_SIGN
-
 /* Library needed by timemodule.c: librt may be needed for clock_gettime() */
 #undef TIMEMODULE_LIB
 
-- 
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