{ext,test}/zlib: Specify frozen_string_literal: true.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57564 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/zlib/extconf.rb

@@ -1,4 +1,4 @@
-# frozen_string_literal: false
+# frozen_string_literal: true
 #
 # extconf.rb
 #

test/zlib/test_zlib.rb

@@ -1,5 +1,5 @@
 # coding: us-ascii
-# frozen_string_literal: false
+# frozen_string_literal: true
 require 'test/unit'
 require 'stringio'
 require 'tempfile'
@@ -42,7 +42,7 @@ if defined? Zlib
     end
 
     def test_deflate_chunked
-      original = ''
+      original = ''.dup
       chunks = []
       r = Random.new 0
 
@@ -315,7 +315,7 @@ if defined? Zlib
 
       z = Zlib::Inflate.new
 
-      inflated = ""
+      inflated = "".dup
 
       deflated.each_char do |byte|
         inflated << z.inflate(byte)
@@ -603,7 +603,7 @@ if defined? Zlib
           assert_equal(t.path, f.path)
         end
 
-        s = ""
+        s = "".dup
         sio = StringIO.new(s)
         gz = Zlib::GzipWriter.new(sio)
         gz.print("foo")
@@ -625,7 +625,7 @@ if defined? Zlib
     end
 
     def test_ungetc
-      s = ""
+      s = "".dup
       w = Zlib::GzipWriter.new(StringIO.new(s))
       w << (1...1000).to_a.inspect
       w.close
@@ -640,7 +640,7 @@ if defined? Zlib
     end
 
     def test_ungetc_paragraph
-      s = ""
+      s = "".dup
       w = Zlib::GzipWriter.new(StringIO.new(s))
       w << "abc"
       w.close
@@ -778,7 +778,7 @@ if defined? Zlib
         end
 
         Zlib::GzipReader.open(t.path) do |f|
-          s = ""
+          s = "".dup
           f.readpartial(3, s)
           assert("foo".start_with?(s))
 
@@ -938,7 +938,7 @@ if defined? Zlib
     end
 
     def test_corrupted_header
-      gz = Zlib::GzipWriter.new(StringIO.new(s = ""))
+      gz = Zlib::GzipWriter.new(StringIO.new(s = "".dup))
       gz.orig_name = "X"
       gz.comment = "Y"
       gz.print("foo")
@@ -1120,7 +1120,7 @@ if defined? Zlib
     def test_deflate_stream
       r = Random.new 0
 
-      deflated = ''
+      deflated = ''.dup
 
       Zlib.deflate(r.bytes(20000)) do |chunk|
         deflated << chunk