about summary refs log tree commit diff
path: root/sysdeps/ieee754
diff options
context:
space:
mode:
authorJoseph Myers <joseph@codesourcery.com>2015-11-03 00:11:49 +0000
committerJoseph Myers <joseph@codesourcery.com>2015-11-03 00:11:49 +0000
commit444ec6b8d8091456a2622765ac60f9c60e7755a9 (patch)
treef070f46708cf30cb4d629348d234fe5735d12f4a /sysdeps/ieee754
parent85422c2acba83852396c9d9fd22ff0493e3606fe (diff)
downloadglibc-444ec6b8d8091456a2622765ac60f9c60e7755a9.tar.gz
glibc-444ec6b8d8091456a2622765ac60f9c60e7755a9.tar.xz
glibc-444ec6b8d8091456a2622765ac60f9c60e7755a9.zip
Fix dbl-64 remainder sign of zero result (bug 19201).
For some large arguments, the dbl-64 implementation of remainder gives
zero results with the wrong sign, resulting from a subtraction that is
mathematically correct but does not guarantee that a zero result has
the sign of the first argument to remainder.  This patch adds an
appropriate check for this case, similar to other implementations of
remainder in the case of equality, and adds tests of remainder on
inputs already used to test remquo.

Tested for x86_64 and x86.

	[BZ #19201]
	* sysdeps/ieee754/dbl-64/e_remainder.c (__ieee754_remainder):
	Check for zero remainder in case of large exponents and ensure
	correct sign of result in that case.
	* math/libm-test.inc (remainder_test_data): Add more tests.
Diffstat (limited to 'sysdeps/ieee754')
-rw-r--r--sysdeps/ieee754/dbl-64/e_remainder.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/sysdeps/ieee754/dbl-64/e_remainder.c b/sysdeps/ieee754/dbl-64/e_remainder.c
index 7f3a02b3c2..4818091231 100644
--- a/sysdeps/ieee754/dbl-64/e_remainder.c
+++ b/sysdeps/ieee754/dbl-64/e_remainder.c
@@ -130,6 +130,8 @@ __ieee754_remainder (double x, double y)
 	      d = fabs (z);
 	      if (d <= fabs (d - y))
 		return z;
+	      else if (d == y)
+		return 0.0 * x;
 	      else
 		return (z > 0) ? z - y : z + y;
 	    }