Fix ctanh (0 + i NaN), ctanh (0 + i Inf) (bug 22568, DR#471).

As per C11 DR#471, ctanh (0 + i NaN) and ctanh (0 + i Inf) should
return 0 + i NaN (with "invalid" exception in the second case but not
the first), not NaN + i NaN.  This has corresponding implications for
ctan since its special cases are defined by ctan (z) = -i ctanh (iz).
This patch implements these cases for ctanh and ctan, updating
tests accordingly.

Tested for x86_64.

	[BZ #22568]
	* math/s_ctan_template.c (M_DECL_FUNC (__ctan)): Set imaginary
	part of result to imaginary part of argument if it is zero and the
	real part of the argument is not finite.
	* math/s_ctanh_template.c (M_DECL_FUNC (__ctanh)): Set real part
	of result to real part of argument if it is zero and the imaginary
	part of the argument is not finite.

4 files changed, 20 insertions, 14 deletions

diff --git a/math/libm-test-ctan.inc b/math/libm-test-ctan.inc
index e485828b8c..0c2c584c3a 100644
--- a/math/libm-test-ctan.inc
+++ b/math/libm-test-ctan.inc
@@ -90,13 +90,13 @@ static const struct test_c_c_data ctan_test_data[] =
     TEST_c_c (ctan, -0x1.2p16383L, minus_infty, 0.0, -1.0),
 #endif
 
-    TEST_c_c (ctan, plus_infty, 0, qnan_value, qnan_value, INVALID_EXCEPTION),
+    TEST_c_c (ctan, plus_infty, 0, qnan_value, 0, INVALID_EXCEPTION),
     TEST_c_c (ctan, plus_infty, 2, qnan_value, qnan_value, INVALID_EXCEPTION),
-    TEST_c_c (ctan, minus_infty, 0, qnan_value, qnan_value, INVALID_EXCEPTION),
+    TEST_c_c (ctan, minus_infty, 0, qnan_value, 0, INVALID_EXCEPTION),
     TEST_c_c (ctan, minus_infty, 2, qnan_value, qnan_value, INVALID_EXCEPTION),
-    TEST_c_c (ctan, plus_infty, minus_zero, qnan_value, qnan_value, INVALID_EXCEPTION),
+    TEST_c_c (ctan, plus_infty, minus_zero, qnan_value, minus_zero, INVALID_EXCEPTION),
     TEST_c_c (ctan, plus_infty, -2, qnan_value, qnan_value, INVALID_EXCEPTION),
-    TEST_c_c (ctan, minus_infty, minus_zero, qnan_value, qnan_value, INVALID_EXCEPTION),
+    TEST_c_c (ctan, minus_infty, minus_zero, qnan_value, minus_zero, INVALID_EXCEPTION),
     TEST_c_c (ctan, minus_infty, -2, qnan_value, qnan_value, INVALID_EXCEPTION),
 
     TEST_c_c (ctan, qnan_value, plus_infty, 0.0, 1.0, IGNORE_ZERO_INF_SIGN),
@@ -112,9 +112,9 @@ static const struct test_c_c_data ctan_test_data[] =
     TEST_c_c (ctan, 0.5, qnan_value, qnan_value, qnan_value, INVALID_EXCEPTION_OK),
     TEST_c_c (ctan, -4.5, qnan_value, qnan_value, qnan_value, INVALID_EXCEPTION_OK),
 
-    TEST_c_c (ctan, qnan_value, 0, qnan_value, qnan_value, INVALID_EXCEPTION_OK),
+    TEST_c_c (ctan, qnan_value, 0, qnan_value, 0),
     TEST_c_c (ctan, qnan_value, 5, qnan_value, qnan_value, INVALID_EXCEPTION_OK),
-    TEST_c_c (ctan, qnan_value, minus_zero, qnan_value, qnan_value, INVALID_EXCEPTION_OK),
+    TEST_c_c (ctan, qnan_value, minus_zero, qnan_value, minus_zero),
     TEST_c_c (ctan, qnan_value, -0.25, qnan_value, qnan_value, INVALID_EXCEPTION_OK),
 
     TEST_c_c (ctan, qnan_value, qnan_value, qnan_value, qnan_value),
diff --git a/math/libm-test-ctanh.inc b/math/libm-test-ctanh.inc
index 6ddeb0d361..8a8148248a 100644
--- a/math/libm-test-ctanh.inc
+++ b/math/libm-test-ctanh.inc
@@ -89,13 +89,13 @@ static const struct test_c_c_data ctanh_test_data[] =
     TEST_c_c (ctanh, minus_infty, -0x1.2p16383L, -1.0, 0.0),
 #endif
 
-    TEST_c_c (ctanh, 0, plus_infty, qnan_value, qnan_value, INVALID_EXCEPTION),
+    TEST_c_c (ctanh, 0, plus_infty, 0, qnan_value, INVALID_EXCEPTION),
     TEST_c_c (ctanh, 2, plus_infty, qnan_value, qnan_value, INVALID_EXCEPTION),
-    TEST_c_c (ctanh, 0, minus_infty, qnan_value, qnan_value, INVALID_EXCEPTION),
+    TEST_c_c (ctanh, 0, minus_infty, 0, qnan_value, INVALID_EXCEPTION),
     TEST_c_c (ctanh, 2, minus_infty, qnan_value, qnan_value, INVALID_EXCEPTION),
-    TEST_c_c (ctanh, minus_zero, plus_infty, qnan_value, qnan_value, INVALID_EXCEPTION),
+    TEST_c_c (ctanh, minus_zero, plus_infty, minus_zero, qnan_value, INVALID_EXCEPTION),
     TEST_c_c (ctanh, -2, plus_infty, qnan_value, qnan_value, INVALID_EXCEPTION),
-    TEST_c_c (ctanh, minus_zero, minus_infty, qnan_value, qnan_value, INVALID_EXCEPTION),
+    TEST_c_c (ctanh, minus_zero, minus_infty, minus_zero, qnan_value, INVALID_EXCEPTION),
     TEST_c_c (ctanh, -2, minus_infty, qnan_value, qnan_value, INVALID_EXCEPTION),
 
     TEST_c_c (ctanh, plus_infty, qnan_value, 1.0, 0.0, IGNORE_ZERO_INF_SIGN),
@@ -111,9 +111,9 @@ static const struct test_c_c_data ctanh_test_data[] =
     TEST_c_c (ctanh, qnan_value, 0.5, qnan_value, qnan_value, INVALID_EXCEPTION_OK),
     TEST_c_c (ctanh, qnan_value, -4.5, qnan_value, qnan_value, INVALID_EXCEPTION_OK),
 
-    TEST_c_c (ctanh, 0, qnan_value, qnan_value, qnan_value, INVALID_EXCEPTION_OK),
+    TEST_c_c (ctanh, 0, qnan_value, 0, qnan_value),
     TEST_c_c (ctanh, 5, qnan_value, qnan_value, qnan_value, INVALID_EXCEPTION_OK),
-    TEST_c_c (ctanh, minus_zero, qnan_value, qnan_value, qnan_value, INVALID_EXCEPTION_OK),
+    TEST_c_c (ctanh, minus_zero, qnan_value, minus_zero, qnan_value),
     TEST_c_c (ctanh, -0.25, qnan_value, qnan_value, qnan_value, INVALID_EXCEPTION_OK),
 
     TEST_c_c (ctanh, qnan_value, qnan_value, qnan_value, qnan_value),
diff --git a/math/s_ctan_template.c b/math/s_ctan_template.c
index 723156eed4..644d7e696d 100644
--- a/math/s_ctan_template.c
+++ b/math/s_ctan_template.c
@@ -49,7 +49,10 @@ M_DECL_FUNC (__ctan) (CFLOAT x)
       else
 	{
 	  __real__ res = M_NAN;
-	  __imag__ res = M_NAN;
+	  if (__imag__ x == 0)
+	    __imag__ res = __imag__ x;
+	  else
+	    __imag__ res = M_NAN;
 
 	  if (isinf (__real__ x))
 	    feraiseexcept (FE_INVALID);
diff --git a/math/s_ctanh_template.c b/math/s_ctanh_template.c
index 96873dd0a3..f237e81511 100644
--- a/math/s_ctanh_template.c
+++ b/math/s_ctanh_template.c
@@ -48,7 +48,10 @@ M_DECL_FUNC (__ctanh) (CFLOAT x)
 	}
       else
 	{
-	  __real__ res = M_NAN;
+	  if (__real__ x == 0)
+	    __real__ res = __real__ x;
+	  else
+	    __real__ res = M_NAN;
 	  __imag__ res = M_NAN;
 
 	  if (isinf (__imag__ x))