merge revision(s) 60d0421ca861944459f52292d65dbf0ece26e38a,b6534691a16d751d59fc572d5dddebcaeb21f007,409dbc951b9875d27bd73748c88e15386473cffb,842b0008c132dd587f09766a228041afb7fed24f: [Backport #18191]

	Fix the encoding of loaded feature names [Bug #18191]

	The feature names loaded from the default load paths should also
	be in the file system encoding.
	---
	 ruby.c                    | 12 +++++++++++-
	 test/ruby/test_require.rb | 22 ++++++++++++++++++++++
	 2 files changed, 33 insertions(+), 1 deletion(-)

	Copy path strings as interned strings

	---
	 ruby.c | 12 ++++++++++--
	 1 file changed, 10 insertions(+), 2 deletions(-)

	Replace expanded load path only when modified

	---
	 ruby.c | 6 +++++-
	 1 file changed, 5 insertions(+), 1 deletion(-)

	Skip broken strings as the locale encoding

	---
	 internal/string.h |  1 +
	 ruby.c            | 11 +++++++----
	 string.c          |  6 ++++++
	 3 files changed, 14 insertions(+), 4 deletions(-)

1 files changed, 22 insertions, 0 deletions

diff --git a/test/ruby/test_require.rb b/test/ruby/test_require.rb
index 52566ecbfb..9b658286c9 100644
--- a/test/ruby/test_require.rb
+++ b/test/ruby/test_require.rb
@@ -531,6 +531,28 @@ class TestRequire < Test::Unit::TestCase
     $".replace(features)
   end
 
+  def test_default_loaded_features_encoding
+    Dir.mktmpdir {|tmp|
+      Dir.mkdir("#{tmp}/1")
+      Dir.mkdir("#{tmp}/2")
+      File.write("#{tmp}/1/bug18191-1.rb", "")
+      File.write("#{tmp}/2/bug18191-2.rb", "")
+      assert_separately(%W[-Eutf-8 -I#{tmp}/1 -], "#{<<~"begin;"}\n#{<<~'end;'}")
+      tmp = #{tmp.dump}"/2"
+      begin;
+        $:.unshift(tmp)
+        require "bug18191-1"
+        require "bug18191-2"
+        encs = [Encoding::US_ASCII, Encoding.find("filesystem")]
+        message = -> {
+          require "pp"
+          {filesystem: encs[1], **$".group_by(&:encoding)}.pretty_inspect
+        }
+        assert($".all? {|n| encs.include?(n.encoding)}, message)
+      end;
+    }
+  end
+
   def test_require_changed_current_dir
     bug7158 = '[ruby-core:47970]'
     Dir.mktmpdir {|tmp|