range.c: fix fixnum loop condition

* range.c (range_step): FIXABLE + FIXABLE never overflow, but may
  not be FIXABLE.  [Feature #12912]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63207 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 3 insertions, 4 deletions

diff --git a/range.c b/range.c
index fb3a4cbaff..71d81fa6c4 100644
--- a/range.c
+++ b/range.c
@@ -402,11 +402,10 @@ range_step(int argc, VALUE *argv, VALUE range)
 
     if (FIXNUM_P(b) && NIL_P(e) && FIXNUM_P(step)) {
 	long i = FIX2LONG(b), unit = FIX2LONG(step);
-	while (1) {
+	do {
 	    rb_yield(LONG2FIX(i));
-	    if (i + unit < i) break;
-	    i += unit;
-	}
+	    i += unit;          /* FIXABLE+FIXABLE never overflow */
+	} while (FIXABLE(i));
 	b = LONG2NUM(i);
 
 	for (;; b = rb_funcallv(b, id_succ, 0, 0))