Fix ctan, ctanh missing underflows (bug 18595).

Similar to various other bugs in this area, ctan and ctanh can fail to
raise the underflow exception for some cases of results that are tiny
and inexact.  This patch forces the exception in a similar way to
previous fixes.

Tested for x86_64 and x86.

	[BZ #18595]
	* math/s_ctan.c (__ctan): Force underflow exception for results
	whose real or imaginary part has small absolute value.
	* math/s_ctanf.c (__ctanf): Likewise.
	* math/s_ctanh.c (__ctanh): Likewise.
	* math/s_ctanhf.c (__ctanhf): Likewise.
	* math/s_ctanhl.c (__ctanhl): Likewise.
	* math/s_ctanl.c (__ctanl): Likewise.
	* math/auto-libm-test-in: Do not allow missing underflow for ctan
	and ctanh.  Add more tests of ctan and ctanh.

ChangeLog

@@ -1,5 +1,16 @@
 2015-09-15  Joseph Myers  <joseph@codesourcery.com>
 
+	[BZ #18595]
+	* math/s_ctan.c (__ctan): Force underflow exception for results
+	whose real or imaginary part has small absolute value.
+	* math/s_ctanf.c (__ctanf): Likewise.
+	* math/s_ctanh.c (__ctanh): Likewise.
+	* math/s_ctanhf.c (__ctanhf): Likewise.
+	* math/s_ctanhl.c (__ctanhl): Likewise.
+	* math/s_ctanl.c (__ctanl): Likewise.
+	* math/auto-libm-test-in: Do not allow missing underflow for ctan
+	and ctanh.  Add more tests of ctan and ctanh.
+
 	[BZ #15918]
 	* sysdeps/ieee754/flt-32/e_hypotf.c (__ieee754_hypotf): Simplify
 	handling of cases where one argument is an infinity.

NEWS

@@ -11,10 +11,10 @@ Version 2.23
 
   2542, 2543, 2558, 2898, 14341, 14912, 15786, 15918, 16141, 16517, 16519,
   16520, 16521, 16734, 16973, 16985, 17787, 17905, 18084, 18086, 18240,
-  18265, 18370, 18421, 18480, 18525, 18610, 18618, 18647, 18661, 18674,
-  18675, 18681, 18757, 18778, 18781, 18787, 18789, 18790, 18795, 18796,
-  18820, 18823, 18824, 18863, 18870, 18873, 18875, 18887, 18921, 18952,
-  18961, 18966.
+  18265, 18370, 18421, 18480, 18525, 18595, 18610, 18618, 18647, 18661,
+  18674, 18675, 18681, 18757, 18778, 18781, 18787, 18789, 18790, 18795,
+  18796, 18820, 18823, 18824, 18863, 18870, 18873, 18875, 18887, 18921,
+  18952, 18961, 18966.
 
 * The obsolete header <regexp.h> has been removed.  Programs that require
   this header must be updated to use <regex.h> instead.

math/auto-libm-test-in

@@ -1245,11 +1245,14 @@ ctan 0x1.921fb6p+0 0x1p-149
 ctan 0x1.921fb54442d18p+0 0x1p-1074
 ctan 0x1.921fb54442d1846ap+0 0x1p-16445
 
-# Bug 18595: underflow exception may be missing
-ctan min 0 missing-underflow
-ctan -min 0 missing-underflow
-ctan min_subnorm 0 missing-underflow
-ctan -min_subnorm 0 missing-underflow
+ctan min 0
+ctan -min 0
+ctan min_subnorm 0
+ctan -min_subnorm 0
+ctan 0 min
+ctan 0 -min
+ctan 0 min_subnorm
+ctan 0 -min_subnorm
 
 ctanh 0 0
 ctanh 0 -0
@@ -1285,11 +1288,14 @@ ctanh 0x1p-149 0x1.921fb6p+0
 ctanh 0x1p-1074 0x1.921fb54442d18p+0
 ctanh 0x1p-16445 0x1.921fb54442d1846ap+0
 
-# Bug 18595: underflow exception may be missing
-ctanh 0 min missing-underflow
-ctanh 0 -min missing-underflow
-ctanh 0 min_subnorm missing-underflow
-ctanh 0 -min_subnorm missing-underflow
+ctanh 0 min
+ctanh 0 -min
+ctanh 0 min_subnorm
+ctanh 0 -min_subnorm
+ctanh min 0
+ctanh -min 0
+ctanh min_subnorm 0
+ctanh -min_subnorm 0
 
 erf 0
 erf -0

math/s_ctan.c

@@ -110,6 +110,16 @@ __ctan (__complex__ double x)
 	  __real__ res = sinrx * cosrx / den;
 	  __imag__ res = sinhix * coshix / den;
 	}
+      if (fabs (__real__ res) < DBL_MIN)
+	{
+	  double force_underflow = __real__ res * __real__ res;
+	  math_force_eval (force_underflow);
+	}
+      if (fabs (__imag__ res) < DBL_MIN)
+	{
+	  double force_underflow = __imag__ res * __imag__ res;
+	  math_force_eval (force_underflow);
+	}
     }
 
   return res;

math/s_ctanf.c

@@ -110,6 +110,16 @@ __ctanf (__complex__ float x)
 	  __real__ res = sinrx * cosrx / den;
 	  __imag__ res = sinhix * coshix / den;
 	}
+      if (fabsf (__real__ res) < FLT_MIN)
+	{
+	  float force_underflow = __real__ res * __real__ res;
+	  math_force_eval (force_underflow);
+	}
+      if (fabsf (__imag__ res) < FLT_MIN)
+	{
+	  float force_underflow = __imag__ res * __imag__ res;
+	  math_force_eval (force_underflow);
+	}
     }
 
   return res;

math/s_ctanh.c

@@ -110,6 +110,16 @@ __ctanh (__complex__ double x)
 	  __real__ res = sinhrx * coshrx / den;
 	  __imag__ res = sinix * cosix / den;
 	}
+      if (fabs (__real__ res) < DBL_MIN)
+	{
+	  double force_underflow = __real__ res * __real__ res;
+	  math_force_eval (force_underflow);
+	}
+      if (fabs (__imag__ res) < DBL_MIN)
+	{
+	  double force_underflow = __imag__ res * __imag__ res;
+	  math_force_eval (force_underflow);
+	}
     }
 
   return res;

math/s_ctanhf.c

@@ -110,6 +110,16 @@ __ctanhf (__complex__ float x)
 	  __real__ res = sinhrx * coshrx / den;
 	  __imag__ res = sinix * cosix / den;
 	}
+      if (fabsf (__real__ res) < FLT_MIN)
+	{
+	  float force_underflow = __real__ res * __real__ res;
+	  math_force_eval (force_underflow);
+	}
+      if (fabsf (__imag__ res) < FLT_MIN)
+	{
+	  float force_underflow = __imag__ res * __imag__ res;
+	  math_force_eval (force_underflow);
+	}
     }
 
   return res;

math/s_ctanhl.c

@@ -117,6 +117,16 @@ __ctanhl (__complex__ long double x)
 	  __real__ res = sinhrx * coshrx / den;
 	  __imag__ res = sinix * cosix / den;
 	}
+      if (fabsl (__real__ res) < LDBL_MIN)
+	{
+	  long double force_underflow = __real__ res * __real__ res;
+	  math_force_eval (force_underflow);
+	}
+      if (fabsl (__imag__ res) < LDBL_MIN)
+	{
+	  long double force_underflow = __imag__ res * __imag__ res;
+	  math_force_eval (force_underflow);
+	}
     }
 
   return res;

math/s_ctanl.c

@@ -117,6 +117,16 @@ __ctanl (__complex__ long double x)
 	  __real__ res = sinrx * cosrx / den;
 	  __imag__ res = sinhix * coshix / den;
 	}
+      if (fabsl (__real__ res) < LDBL_MIN)
+	{
+	  long double force_underflow = __real__ res * __real__ res;
+	  math_force_eval (force_underflow);
+	}
+      if (fabsl (__imag__ res) < LDBL_MIN)
+	{
+	  long double force_underflow = __imag__ res * __imag__ res;
+	  math_force_eval (force_underflow);
+	}
     }
 
   return res;