math.c: fix for Bignum argument

* math.c (math_log, math_log2, math_log10): fix for Bignum argument.
  numbits should be add only when right shifted.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43080 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 12 insertions, 3 deletions

diff --git a/math.c b/math.c
index d9c76334c8..e621d1af77 100644
--- a/math.c
+++ b/math.c
@@ -442,7 +442,7 @@ math_log(int argc, VALUE *argv)
 {
     VALUE x, base;
     double d0, d;
-    size_t numbits = 0;
+    size_t numbits;
 
     rb_scan_args(argc, argv, "11", &x, &base);
 
@@ -451,6 +451,9 @@ math_log(int argc, VALUE *argv)
         numbits -= DBL_MANT_DIG;
         x = rb_big_rshift(x, SIZET2NUM(numbits));
     }
+    else {
+	numbits = 0;
+    }
 
     Need_Float(x);
     d0 = RFLOAT_VALUE(x);
@@ -501,13 +504,16 @@ static VALUE
 math_log2(VALUE obj, VALUE x)
 {
     double d0, d;
-    size_t numbits = 0;
+    size_t numbits;
 
     if (RB_BIGNUM_TYPE_P(x) && RBIGNUM_POSITIVE_P(x) &&
             DBL_MAX_EXP <= (numbits = rb_absint_numwords(x, 1, NULL))) {
         numbits -= DBL_MANT_DIG;
         x = rb_big_rshift(x, SIZET2NUM(numbits));
     }
+    else {
+	numbits = 0;
+    }
 
     Need_Float(x);
     d0 = RFLOAT_VALUE(x);
@@ -540,13 +546,16 @@ static VALUE
 math_log10(VALUE obj, VALUE x)
 {
     double d0, d;
-    size_t numbits = 0;
+    size_t numbits;
 
     if (RB_BIGNUM_TYPE_P(x) && RBIGNUM_POSITIVE_P(x) &&
             DBL_MAX_EXP <= (numbits = rb_absint_numwords(x, 1, NULL))) {
         numbits -= DBL_MANT_DIG;
         x = rb_big_rshift(x, SIZET2NUM(numbits));
     }
+    else {
+	numbits = 0;
+    }
 
     Need_Float(x);
     d0 = RFLOAT_VALUE(x);