From: Joseph Myers <joseph@codesourcery.com>
Date: Mon, 9 Apr 2012 09:43:18 +0000 (+0000)
Subject: Fix missing overflow exceptions from pow (bug 13873).
X-Git-Tag: glibc-2.16-tps~629
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d7dd94539899466a9a4e38c61ab846ffcb314dad;p=thirdparty%2Fglibc.git

Fix missing overflow exceptions from pow (bug 13873).
---

diff --git a/ChangeLog b/ChangeLog
index 6c4bd0732af..75a5ca81376 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 5bd167709ba..a17f611ff37 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 b9ff9f3ad28..05334837492 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 26ffaaddc66..6c41af93ba4 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;