Refactor `mrb_str_to_cstr` and `mrb_string_value_cstr`

- Extract null byte check to function.
- Avoid string allocation if null byte is included.
- Use `str_new` instead of `mrb_str_dup` + `mrb_str_modify`

1 files changed, 3 insertions, 0 deletions

diff --git a/mrbgems/mruby-io/test/file.rb b/mrbgems/mruby-io/test/file.rb
index 88ced31a6..1535ebb44 100644
--- a/mrbgems/mruby-io/test/file.rb
+++ b/mrbgems/mruby-io/test/file.rb
@@ -33,6 +33,7 @@ assert('File.basename') do
   assert_equal 'a', File.basename('/a/')
   assert_equal 'b', File.basename('/a/b')
   assert_equal 'b', File.basename('../a/b')
+  assert_raise(ArgumentError) { File.basename("/a/b\0") }
 end
 
 assert('File.dirname') do
@@ -106,6 +107,8 @@ assert('File.realpath') do
       MRubyIOTestUtil.rmdir dir
     end
   end
+
+  assert_raise(ArgumentError) { File.realpath("TO\0DO") }
 end
 
 assert("File.readlink") do