Getting undefined conversion for '' from ASCII-8BIT to US-ASCII from Zlib::GzipWriter#close

[myronmarston]

# use_zlib.rb

require 'stringio'
require 'zlib'

io = StringIO.new

writer = Zlib::GzipWriter.new(io)
writer << 'th'
writer.close

On a freshly installed rubinius:

➜  ruby --version
rubinius 2.0.0dev (1.9.3 66191c9f yyyy-mm-dd JI) [x86_64-apple-darwin10.8.0]
➜  ruby use_zlib.rb 
An exception occurred running use_zlib.rb
    undefined conversion for '' from ASCII-8BIT to US-ASCII (Rubinius::EncodingClass::Encoding::CompatibilityError)

Backtrace:
       Rubinius::Type.compatible_encoding at kernel/common/type19.rb:28
                                String#<< at kernel/common/string19.rb:397
                           StringIO#write at /Users/myron/.rvm/rubies/rbx-head/lib/19/stringio.rb:124
               Zlib::GzipWriter#write_raw at /Users/myron/.rvm/rubies/rbx-head/lib/zlib.rb:1433
                 Zlib::GzipWriter#end_run at /Users/myron/.rvm/rubies/rbx-head/lib/zlib.rb:1320
     Zlib::GzipFile(Zlib::GzipWriter)#end at /Users/myron/.rvm/rubies/rbx-head/lib/zlib.rb:915
  Zlib::GzipFile(Zlib::GzipWriter)#finish at /Users/myron/.rvm/rubies/rbx-head/lib/zlib.rb:927
   Zlib::GzipFile(Zlib::GzipWriter)#close at /Users/myron/.rvm/rubies/rbx-head/lib/zlib.rb:885
                        Object#__script__ at use_zlib.rb:10
         Rubinius::CodeLoader#load_script at kernel/delta/codeloader.rb:67
         Rubinius::CodeLoader.load_script at kernel/delta/codeloader.rb:109
                  Rubinius::Loader#script at kernel/loader.rb:640
                    Rubinius::Loader#main at kernel/loader.rb:844

[myronmarston]

One strange thing about this: the content being written seems to matter. If you change 'th' to 'abc', it works. No idea why.

[dbussink]

This has been fixed by switching to MRI's zlib in 9aa6a37