sprintf.c: fix garbage inserted with Rational

* sprintf.c (rb_str_format): fix wrong shifting position in
  Rational conversion when not at the beginning of the result.
  [ruby-core:71806] [Bug #11766]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52869 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,9 @@
+Thu Dec  3 15:33:08 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* sprintf.c (rb_str_format): fix wrong shifting position in
+	  Rational conversion when not at the beginning of the result.
+	  [ruby-core:71806] [Bug #11766]
+
 Thu Dec  3 14:22:16 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* range.c (range_to_s): should be infected by the receiver.

sprintf.c

@@ -1107,16 +1107,19 @@ rb_str_format(int argc, const VALUE *argv, VALUE fmt)
 		    done += prec;
 		}
 		if ((flags & FWIDTH) && width > done) {
+		    int fill = ' ';
+		    long shifting = 0;
 		    if (!(flags&FMINUS)) {
-			long i, shifting = (flags&FZERO) ? done - prefix : done;
-			for (i = 1; i <= shifting; i++)
-			    buf[width - i] = buf[done - i];
+			shifting = done;
+			if (flags&FZERO) {
+			    shifting -= prefix;
+			    fill = '0';
+			}
 			blen -= shifting;
-			FILL((flags&FZERO) ? '0' : ' ', width - done);
-			blen += shifting;
-		    } else {
-			FILL(' ', width - done);
+			memmove(&buf[blen + width - done], &buf[blen], shifting);
 		    }
+		    FILL(fill, width - done);
+		    blen += shifting;
 		}
 		RB_GC_GUARD(val);
 		break;

test/ruby/test_sprintf.rb

@@ -166,6 +166,9 @@ class TestSprintf < Test::Unit::TestCase
         end
       end
     end
+
+    bug11766 = '[ruby-core:71806] [Bug #11766]'
+    assert_equal("x"*10+"     1.0", sprintf("x"*10+"%8.1f", 1r))
   end
 
   def test_hash