math.c: more accuracy

* math.c (math_log10): calculate log10(2) for more accuracy.
  [ruby-core:79907] [Bug #13279]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57779 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 1 deletions

diff --git a/math.c b/math.c
index 74dff9e720..523937ecb3 100644
--- a/math.c
+++ b/math.c
@@ -563,7 +563,7 @@ math_log10(VALUE unused_obj, VALUE x)
     /* check for pole error */
     if (d == 0.0) return DBL2NUM(-INFINITY);
 
-    return DBL2NUM(log10(d) + numbits * M_LN2/M_LN10); /* log10(d * 2 ** numbits) */
+    return DBL2NUM(log10(d) + numbits * log10(2)); /* log10(d * 2 ** numbits) */
 }
 
 /*