* util.c (ruby_strtod): this code uses FPU's rounding system.

  But x86's FPU calculates double precision floating-point
  numbers in 80bit precision, so it fails to round the value.
  So ensure the value is assigned a variable. [ruby-dev:42551]
  see also [ruby-math:00802]
  http://www.shudo.net/java-grandprix99/strictfp/

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@29729 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 5 insertions, 2 deletions

diff --git a/util.c b/util.c
index 0b69b6cfb7..bc307e4636 100644
--- a/util.c
+++ b/util.c
@@ -4014,10 +4014,13 @@ ruby_hdtoa(double d, const char *xdigs, int ndigits, int *decpt, int *sign,
 	/* Round to the desired number of digits. */
 	if (SIGFIGS > ndigits && ndigits > 0) {
 		float redux = 1.0f;
+		volatile double d;
 		int offset = 4 * ndigits + DBL_MAX_EXP - 4 - DBL_MANT_DIG;
 		dexp_set(u, offset);
-		u.d += redux;
-		u.d -= redux;
+		d = u.d;
+		d += redux;
+		d -= redux;
+		u.d = d;
 		*decpt += dexp_get(u) - offset;
 	}