Fix pow (0.0, -Inf) (bug 14241).

git-mirror · Jun 15, 2012 · 10285c2 · 10285c2
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commit 10285c2
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diff --git a/ChangeLog b/ChangeLog
@@ -1,3 +1,11 @@
+2012-06-15  Joseph Myers  <joseph@codesourcery.com>
+
+	[BZ #14241]
+	* sysdeps/ieee754/dbl-64/e_pow.c (__ieee754_pow): Use 0.0 instead
+	of ABS(x) in calculating zero to negative powers other than odd
+	integers.
+	* math/libm-test.inc (pow_test): Add more tests.
+
 2012-06-15  Andreas Jaeger  <aj@suse.de>
 
 	* manual/contrib.texi (Contributors): Update entry of Liubov

diff --git a/NEWS b/NEWS
@@ -29,7 +29,7 @@ Version 2.16
   13963, 13967, 13968, 13970, 13973, 13979, 13983, 13986, 13996, 14012,
   14027, 14033, 14034, 14036, 14040, 14043, 14044, 14048, 14049, 14053,
   14055, 14059, 14064, 14075, 14080, 14083, 14103, 14104, 14109, 14112,
-  14122, 14123, 14134, 14153, 14183, 14188, 14199, 14210, 14218
+  14122, 14123, 14134, 14153, 14183, 14188, 14199, 14210, 14218, 14241
 
 * Support for the x32 ABI on x86-64 added.  The x32 target is selected by
   configuring glibc with:

diff --git a/math/libm-test.inc b/math/libm-test.inc
@@ -6290,6 +6290,8 @@ pow_test (void)
   TEST_ff_f (pow, minus_zero, 11.1L, 0);
   TEST_ff_f (pow, 0, plus_infty, 0);
   TEST_ff_f (pow, minus_zero, plus_infty, 0);
+  TEST_ff_f (pow, 0, minus_infty, plus_infty, DIVIDE_BY_ZERO_EXCEPTION_OK);
+  TEST_ff_f (pow, minus_zero, minus_infty, plus_infty, DIVIDE_BY_ZERO_EXCEPTION_OK);
 
 #ifndef TEST_INLINE
   /* pow (x, +inf) == +inf for |x| > 1.  */

diff --git a/sysdeps/ieee754/dbl-64/e_pow.c b/sysdeps/ieee754/dbl-64/e_pow.c
@@ -112,12 +112,12 @@ __ieee754_pow(double x, double y) {
     if (((v.i[HIGH_HALF] & 0x7fffffff) == 0x7ff00000 && v.i[LOW_HALF] != 0)
 	|| (v.i[HIGH_HALF] & 0x7fffffff) > 0x7ff00000)
       return y;
-    if (ABS(y) > 1.0e20) return (y>0)?0:1.0/ABS(x);
+    if (ABS(y) > 1.0e20) return (y>0)?0:1.0/0.0;
     k = checkint(y);
     if (k == -1)
       return y < 0 ? 1.0/x : x;
     else
-      return y < 0 ? 1.0/ABS(x) : 0.0;                               /* return 0 */
+      return y < 0 ? 1.0/0.0 : 0.0;                               /* return 0 */
   }
 
   qx = u.i[HIGH_HALF]&0x7fffffff;  /*   no sign   */