revert r57323

StringIO.new makes the buffer IO.default_external, while
StringIO.new("".dup) makes source encoding which is defaulted to
UTF-8.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57328 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/net/protocol/test_protocol.rb

@@ -6,7 +6,7 @@
 class TestProtocol < Test::Unit::TestCase
   def test_should_properly_dot_stuff_period_with_no_endline
     bug9627 = '[ruby-core:61441] [Bug #9627]'
-    sio = StringIO.new
+    sio = StringIO.new("".dup)
     imio = Net::InternetMessageIO.new(sio)
     email = "To: bob@aol.com\nlook, a period with no endline\n."
     imio.write_message(email)
@@ -15,12 +15,12 @@ def test_should_properly_dot_stuff_period_with_no_endline
 
   def test_each_crlf_line
     assert_output('', '') do
-      sio = StringIO.new
+      sio = StringIO.new("".dup)
       imio = Net::InternetMessageIO.new(sio)
       assert_equal(23, imio.write_message("\u3042\r\u3044\n\u3046\r\n\u3048"))
       assert_equal("\u3042\r\n\u3044\r\n\u3046\r\n\u3048\r\n.\r\n", sio.string)
 
-      sio = StringIO.new
+      sio = StringIO.new("".dup)
       imio = Net::InternetMessageIO.new(sio)
       assert_equal(8, imio.write_message("\u3042\r"))
       assert_equal("\u3042\r\n.\r\n", sio.string)

test/open-uri/test_open-uri.rb

@@ -246,7 +246,7 @@ def test_non_http_proxy
 
   def test_proxy
     with_http {|srv, dr, url|
-      proxy_log = StringIO.new
+      proxy_log = StringIO.new(''.dup)
       proxy_logger = WEBrick::Log.new(proxy_log, WEBrick::BasicLog::WARN)
       proxy_auth_log = ''.dup
       proxy = WEBrick::HTTPProxyServer.new({
@@ -300,7 +300,7 @@ def test_proxy
 
   def test_proxy_http_basic_authentication_failure
     with_http {|srv, dr, url|
-      proxy_log = StringIO.new
+      proxy_log = StringIO.new(''.dup)
       proxy_logger = WEBrick::Log.new(proxy_log, WEBrick::BasicLog::WARN)
       proxy_auth_log = ''.dup
       proxy = WEBrick::HTTPProxyServer.new({
@@ -333,7 +333,7 @@ def test_proxy_http_basic_authentication_failure
 
   def test_proxy_http_basic_authentication_success
     with_http {|srv, dr, url|
-      proxy_log = StringIO.new
+      proxy_log = StringIO.new(''.dup)
       proxy_logger = WEBrick::Log.new(proxy_log, WEBrick::BasicLog::WARN)
       proxy_auth_log = ''.dup
       proxy = WEBrick::HTTPProxyServer.new({
@@ -374,7 +374,7 @@ def test_proxy_http_basic_authentication_success
 
   def test_authenticated_proxy_http_basic_authentication_success
     with_http {|srv, dr, url|
-      proxy_log = StringIO.new
+      proxy_log = StringIO.new(''.dup)
       proxy_logger = WEBrick::Log.new(proxy_log, WEBrick::BasicLog::WARN)
       proxy_auth_log = ''.dup
       proxy = WEBrick::HTTPProxyServer.new({

test/zlib/test_zlib.rb

@@ -1,5 +1,5 @@
 # coding: us-ascii
-# frozen_string_literal: true
+# frozen_string_literal: false
 require 'test/unit'
 require 'stringio'
 require 'tempfile'
@@ -42,7 +42,7 @@ def test_deflate
     end
 
     def test_deflate_chunked
-      original = String.new
+      original = ''
       chunks = []
       r = Random.new 0
 
@@ -315,7 +315,7 @@ def test_inflate_partial_input
 
       z = Zlib::Inflate.new
 
-      inflated = String.new
+      inflated = ""
 
       deflated.each_char do |byte|
         inflated << z.inflate(byte)
@@ -603,13 +603,14 @@ def test_path
           assert_equal(t.path, f.path)
         end
 
-        sio = StringIO.new
+        s = ""
+        sio = StringIO.new(s)
         gz = Zlib::GzipWriter.new(sio)
         gz.print("foo")
         assert_raise(NoMethodError) { gz.path }
         gz.close
 
-        sio = StringIO.new(sio.string)
+        sio = StringIO.new(s)
         Zlib::GzipReader.new(sio) do |f|
           assert_raise(NoMethodError) { f.path }
         end
@@ -624,11 +625,11 @@ def test_read0
     end
 
     def test_ungetc
-      sio = StringIO.new
-      w = Zlib::GzipWriter.new(sio)
+      s = ""
+      w = Zlib::GzipWriter.new(StringIO.new(s))
       w << (1...1000).to_a.inspect
       w.close
-      r = Zlib::GzipReader.new(StringIO.new(sio.string))
+      r = Zlib::GzipReader.new(StringIO.new(s))
       r.read(100)
       r.ungetc ?a
       assert_nothing_raised("[ruby-dev:24060]") {
@@ -639,11 +640,11 @@ def test_ungetc
     end
 
     def test_ungetc_paragraph
-      sio = StringIO.new
-      w = Zlib::GzipWriter.new(sio)
+      s = ""
+      w = Zlib::GzipWriter.new(StringIO.new(s))
       w << "abc"
       w.close
-      r = Zlib::GzipReader.new(StringIO.new(sio.string))
+      r = Zlib::GzipReader.new(StringIO.new(s))
       r.ungetc ?\n
       assert_equal("abc", r.gets(""))
       assert_nothing_raised("[ruby-dev:24065]") {
@@ -777,7 +778,7 @@ def test_readpartial
         end
 
         Zlib::GzipReader.open(t.path) do |f|
-          s = String.new
+          s = ""
           f.readpartial(3, s)
           assert("foo".start_with?(s))
 
@@ -937,9 +938,7 @@ def test_reader_wrap
     end
 
     def test_corrupted_header
-      sio = StringIO.new
-      s = sio.string
-      gz = Zlib::GzipWriter.new(sio)
+      gz = Zlib::GzipWriter.new(StringIO.new(s = ""))
       gz.orig_name = "X"
       gz.comment = "Y"
       gz.print("foo")
@@ -1121,7 +1120,7 @@ def test_deflate
     def test_deflate_stream
       r = Random.new 0
 
-      deflated = String.new
+      deflated = ''
 
       Zlib.deflate(r.bytes(20000)) do |chunk|
         deflated << chunk