Fix missing overflow exceptions from pow (bug 13873).

4 files changed, 19 insertions, 15 deletions

diff --git a/ChangeLog b/ChangeLog
index 6c4bd0732a..75a5ca8137 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
 2012-04-09  Joseph Myers  <joseph@codesourcery.com>
 
+	[BZ #13873]
+	* sysdeps/ieee754/dbl-64/e_pow.c (huge, tiny): New variables.
+	(__ieee754_pow): Generate overflow and underflow using huge*huge
+	and tiny*tiny rather than just returning constant infinity or zero
+	for large exponents.
+	* math/libm-test.inc (pow_test): Require overflow exceptions for
+	applicable cases of large exponents.
+
 	[BZ #706]
 	* sysdeps/i386/fpu/e_pow.S (p10): New object.
 	(__ieee754_pow): Use iterative multiplication algorithm only for
diff --git a/NEWS b/NEWS
index 5bd167709b..a17f611ff3 100644
--- a/NEWS
+++ b/NEWS
@@ -18,9 +18,9 @@ Version 2.16
   13533, 13547, 13551, 13552, 13553, 13555, 13559, 13566, 13583, 13592,
   13618, 13637, 13656, 13658, 13673, 13691, 13695, 13704, 13705, 13706,
   13726, 13738, 13760, 13761, 13786, 13792, 13806, 13824, 13840, 13841,
-  13844, 13846, 13851, 13852, 13854, 13871, 13879, 13883, 13892, 13895,
-  13908, 13910, 13911, 13912, 13913, 13915, 13916, 13917, 13918, 13919,
-  13920, 13921, 13926, 13928, 13938
+  13844, 13846, 13851, 13852, 13854, 13871, 13873, 13879, 13883, 13892,
+  13895, 13908, 13910, 13911, 13912, 13913, 13915, 13916, 13917, 13918,
+  13919, 13920, 13921, 13926, 13928, 13938
 
 * ISO C11 support:
 
diff --git a/math/libm-test.inc b/math/libm-test.inc
index b9ff9f3ad2..0533483749 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -5621,8 +5621,7 @@ pow_test (void)
 
   TEST_ff_f (pow, 0x1p72L, 0x1p72L, plus_infty, OVERFLOW_EXCEPTION);
   TEST_ff_f (pow, 10, -0x1p72L, 0);
-  /* Bug 13873: OVERFLOW exception may be missing.  */
-  TEST_ff_f (pow, max_value, max_value, plus_infty, OVERFLOW_EXCEPTION_OK);
+  TEST_ff_f (pow, max_value, max_value, plus_infty, OVERFLOW_EXCEPTION);
   /* Bug 13872: spurious OVERFLOW exception may be present.  */
   TEST_ff_f (pow, 10, -max_value, 0, OVERFLOW_EXCEPTION_OK);
 
@@ -5908,8 +5907,7 @@ pow_test (void)
   TEST_ff_f (pow, -2.0, 0x1.ffffffffffffffffffffffffffffp+113L, plus_infty, OVERFLOW_EXCEPTION);
 # endif
 #endif
-  /* Bug 13873: OVERFLOW exception may be missing.  */
-  TEST_ff_f (pow, -2.0, max_value, plus_infty, OVERFLOW_EXCEPTION_OK);
+  TEST_ff_f (pow, -2.0, max_value, plus_infty, OVERFLOW_EXCEPTION);
 
   TEST_ff_f (pow, -max_value, 0.5, nan_value, INVALID_EXCEPTION);
   TEST_ff_f (pow, -max_value, 1.5, nan_value, INVALID_EXCEPTION);
@@ -5962,8 +5960,7 @@ pow_test (void)
   TEST_ff_f (pow, -max_value, 0x1.ffffffffffffffffffffffffffffp+113L, plus_infty, OVERFLOW_EXCEPTION);
 # endif
 #endif
-  /* Bug 13873: OVERFLOW exception may be missing.  */
-  TEST_ff_f (pow, -max_value, max_value, plus_infty, OVERFLOW_EXCEPTION_OK);
+  TEST_ff_f (pow, -max_value, max_value, plus_infty, OVERFLOW_EXCEPTION);
 
   TEST_ff_f (pow, -0.5, 126, 0x1p-126);
   TEST_ff_f (pow, -0.5, 127, -0x1p-127);
@@ -5990,8 +5987,7 @@ pow_test (void)
   TEST_ff_f (pow, -0.5, -0x1.ffffffffffffffffffffffffffffp+113L, plus_infty, OVERFLOW_EXCEPTION);
 # endif
 #endif
-  /* Bug 13873: OVERFLOW exception may be missing.  */
-  TEST_ff_f (pow, -0.5, -max_value, plus_infty, OVERFLOW_EXCEPTION_OK);
+  TEST_ff_f (pow, -0.5, -max_value, plus_infty, OVERFLOW_EXCEPTION);
 
   TEST_ff_f (pow, -0.5, 0xffffff, minus_zero);
   TEST_ff_f (pow, -0.5, 0x1fffffe, plus_zero);
@@ -6044,8 +6040,7 @@ pow_test (void)
   TEST_ff_f (pow, -min_value, -0x1.ffffffffffffffffffffffffffffp+113L, plus_infty, OVERFLOW_EXCEPTION);
 # endif
 #endif
-  /* Bug 13873: OVERFLOW exception may be missing.  */
-  TEST_ff_f (pow, -min_value, -max_value, plus_infty, OVERFLOW_EXCEPTION_OK);
+  TEST_ff_f (pow, -min_value, -max_value, plus_infty, OVERFLOW_EXCEPTION);
 
   TEST_ff_f (pow, -min_value, 0xffffff, minus_zero);
   TEST_ff_f (pow, -min_value, 0x1fffffe, plus_zero);
diff --git a/sysdeps/ieee754/dbl-64/e_pow.c b/sysdeps/ieee754/dbl-64/e_pow.c
index 26ffaaddc6..6c41af93ba 100644
--- a/sysdeps/ieee754/dbl-64/e_pow.c
+++ b/sysdeps/ieee754/dbl-64/e_pow.c
@@ -47,6 +47,7 @@
 # define SECTION
 #endif
 
+static const double huge = 1.0e300, tiny = 1.0e-300;
 
 double __exp1(double x, double xx, double error);
 static double log1(double x, double *delta, double *error);
@@ -156,8 +157,8 @@ __ieee754_pow(double x, double y) {
 
   if (qy > 0x45f00000 && qy < 0x7ff00000) {
     if (x == 1.0) return 1.0;
-    if (y>0) return (x>1.0)?INF.x:0;
-    if (y<0) return (x<1.0)?INF.x:0;
+    if (y>0) return (x>1.0)?huge*huge:tiny*tiny;
+    if (y<0) return (x<1.0)?huge*huge:tiny*tiny;
   }
 
   if (x == 1.0) return 1.0;