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.

diff --git a/ChangeLog b/ChangeLog
index d9c0689b6ac3c63b58e8e8f67c8dac5a7a0f9132..f80437100beb87ec95e9dfbb585f5ebd13e1789a 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2015-11-02  Joseph Myers  <joseph@codesourcery.com>
 
+       [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.
+
        [BZ #6799]
        * math/s_nextafter.c: Include <errno.h>.
        (__nextafter): Set errno on overflow and underflow.

diff --git a/NEWS b/NEWS
index 1cc08a0a7cb8bcbf8372344be4df62919a6043a0..896eb02887e2b9741f6538d0a6a38b6a430251a3 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -21,7 +21,8 @@ Version 2.23
   18966, 18967, 18969, 18970, 18977, 18980, 18981, 18982, 18985, 19003,
   19007, 19012, 19016, 19018, 19032, 19046, 19048, 19049, 19050, 19059,
   19071, 19074, 19076, 19077, 19078, 19079, 19085, 19086, 19088, 19094,
-  19095, 19124, 19125, 19129, 19134, 19137, 19156, 19174, 19181, 19189.
+  19095, 19124, 19125, 19129, 19134, 19137, 19156, 19174, 19181, 19189,
+  19201.
 
 * A defect in the malloc implementation, present since glibc 2.15 (2012) or
   glibc 2.10 via --enable-experimental-malloc (2009), could result in the

diff --git a/math/libm-test.inc b/math/libm-test.inc
index 1267b817e77bed5a100e7560fcb4333f805d363b..2645ccc147a3b2105d4d3e2167f0e14d5c52ae77 100644 (file)
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -10318,6 +10318,75 @@ static const struct test_ff_f_data remainder_test_data[] =
 #if defined TEST_LDOUBLE && LDBL_MANT_DIG >= 56
     TEST_ff_f (remainder, -0x1.80000000000002p1L, 2.0, 0x1.fffffffffffff8p-1L, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
 #endif
+
+    TEST_ff_f (remainder, 3419, 360, 179, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -3419, 360, -179, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, 3419, -360, 179, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -3419, -360, -179, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+
+    TEST_ff_f (remainder, max_value, max_value, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, max_value, -max_value, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, max_value, min_value, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, max_value, -min_value, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, max_value, min_subnorm_value, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, max_value, -min_subnorm_value, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -max_value, max_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -max_value, -max_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -max_value, min_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -max_value, -min_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -max_value, min_subnorm_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -max_value, -min_subnorm_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, min_value, max_value, min_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, min_value, -max_value, min_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, min_value, min_value, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, min_value, -min_value, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, min_value, min_subnorm_value, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, min_value, -min_subnorm_value, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -min_value, max_value, -min_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -min_value, -max_value, -min_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -min_value, min_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -min_value, -min_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -min_value, min_subnorm_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -min_value, -min_subnorm_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, min_subnorm_value, max_value, min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, min_subnorm_value, -max_value, min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, min_subnorm_value, min_value, min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, min_subnorm_value, -min_value, min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, min_subnorm_value, min_subnorm_value, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, min_subnorm_value, -min_subnorm_value, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -min_subnorm_value, max_value, -min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -min_subnorm_value, -max_value, -min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -min_subnorm_value, min_value, -min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -min_subnorm_value, -min_value, -min_subnorm_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -min_subnorm_value, min_subnorm_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -min_subnorm_value, -min_subnorm_value, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+
+    TEST_ff_f (remainder, 1, max_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, 1, -max_value, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, 1, max_value / 2, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, 1, -max_value / 2, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, 1, max_value / 4, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, 1, -max_value / 4, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, 1, max_value / 8, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, 1, -max_value / 8, 1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -1, max_value, -1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -1, -max_value, -1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -1, max_value / 2, -1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -1, -max_value / 2, -1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -1, max_value / 4, -1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -1, -max_value / 4, -1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -1, max_value / 8, -1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -1, -max_value / 8, -1, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+
+    TEST_ff_f (remainder, max_value, max_value / 2, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, max_value, -max_value / 2, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -max_value, max_value / 2, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -max_value, -max_value / 2, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+
+    TEST_ff_f (remainder, 2, 1, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, 2, -1, plus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -2, 1, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (remainder, -2, -1, minus_zero, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
   };
 
 static void

diff --git a/sysdeps/ieee754/dbl-64/e_remainder.c b/sysdeps/ieee754/dbl-64/e_remainder.c
index 7f3a02b3c24beb32a5c88762fd7ddb78ed57788c..48180912310e92f21cdab28786acc47bde3187e5 100644 (file)
--- 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;
            }