[PATCH v2] file.c (rb_file_s_readlink): do not set invalid encoding

[PATCH v2] file.c (rb_file_s_readlink): do not set invalid encoding

[Eric Wong]

With the exception of '\0', POSIX allows arbitrary bytes in a
symlink.  So we should not assume rb_filesystem_encoding()
is correct, and fall back to ASCII-8BIT if we detect strange
characters.

* file.c (rb_file_s_readlink): fall back to ASCII-8BIT
* test/ruby/test_file_exhaustive.rb (test_readlink_binary): add
  [ruby-core:73582] [Bug #12034]
---
 file.c                            | 10 +++++++++-
 test/ruby/test_file_exhaustive.rb | 16 ++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/file.c b/file.c
index 9f430a3..f880411 100644
--- a/file.c
+++ b/file.c
@@ -2768,7 +2768,15 @@ rb_file_s_symlink(VALUE klass, VALUE from, VALUE to)
 static VALUE
 rb_file_s_readlink(VALUE klass, VALUE path)
 {
-    return rb_readlink(path, rb_filesystem_encoding());
+    VALUE str = rb_readlink(path, rb_filesystem_encoding());
+    int cr = rb_enc_str_coderange(str);
+
+    /* POSIX allows arbitrary bytes with the exception of '\0' */
+    if (cr == ENC_CODERANGE_BROKEN) {
+	rb_enc_associate(str, rb_ascii8bit_encoding());
+    }
+
+    return str;
 }
 
 #ifndef _WIN32
diff --git a/test/ruby/test_file_exhaustive.rb b/test/ruby/test_file_exhaustive.rb
index 53b867e..730000b 100644
--- a/test/ruby/test_file_exhaustive.rb
+++ b/test/ruby/test_file_exhaustive.rb
@@ -549,6 +549,22 @@ def test_readlink
   rescue NotImplementedError
   end
 
+  def test_readlink_binary
+    return unless symlinkfile
+    bug12034 = '[ruby-core:73582] [Bug #12034]'
+    Dir.mktmpdir('rubytest-file-readlink') do |tmpdir|
+      Dir.chdir(tmpdir) do
+        link = "\xde\xad\xbe\xef".b
+        File.symlink(link, 'foo')
+        str = File.readlink('foo')
+        assert_predicate str, :valid_encoding?, bug12034
+        assert_equal link, str, bug12034
+      end
+    end
+  rescue NotImplementedError => e
+    skip "#{e.message} (#{e.class})"
+  end
+
   def test_readlink_long_path
     return unless symlinkfile
     bug9157 = '[ruby-core:58592] [Bug #9157]'
-- 
EW