io.c: IO#write without args returns 0

This is consistent with other implementations of .write
in openssl and stringio.

* io.c (io_write_m): return 0 on argc == 0
  [ruby-core:86285] [Bug #14338]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62967 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

io.c

@@ -1678,7 +1678,7 @@ io_writev(int argc, VALUE *argv, VALUE io)
 static VALUE
 io_write_m(int argc, VALUE *argv, VALUE io)
 {
-    if (argc > 1) {
+    if (argc != 1) {
 	return io_writev(argc, argv, io);
     }
     else {

test/ruby/test_io.rb

@@ -1287,6 +1287,13 @@ class TestIO < Test::Unit::TestCase
     assert_empty(err)
   end
 
+  def test_write_no_args
+    IO.pipe do |r, w|
+      assert_equal 0, w.write, '[ruby-core:86285] [Bug #14338]'
+      assert_equal :wait_readable, r.read_nonblock(1, exception: false)
+    end
+  end
+
   def test_write_non_writable
     with_pipe do |r, w|
       assert_raise(IOError) do