Environment

• jruby 9.1.5.0 (2.3.1) 2016-09-07 036ce39 OpenJDK 64-Bit Server VM 25.91-b14 on 1.8.0_91-8u91-b14-3ubuntu1~16.04.1-b14 +jit [linux-x86_64]
• Linux ubuntu 4.4.0-45-generic #66-Ubuntu SMP Wed Oct 19 14:12:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

Expected Behavior

MRI Zlib::GzipWriter.wrap documentation says: "If you want to keep the associated IO object open, you may call #finish method in the block." (https://ruby-doc.org/stdlib-2.3.1/libdoc/zlib/rdoc/Zlib/GzipFile.html#method-c-wrap). Here is ruby MRI 2.3.1 example:

require 'zlib'
out = StringIO.new
Zlib::GzipWriter.wrap(out) { |gz| gz.finish }
out.closed? # => false
out.tap(&:rewind).read # => "\u001F\x8B\b\u0000ڸ\u0010X\u0000\u0003\u0003\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000"

I expected the same behavior with JRuby.

Actual Behavior

require 'zlib'
out = StringIO.new
Zlib::GzipWriter.wrap(out) { |gz| gz.finish }
out.closed? # => true
out.tap(&:rewind).read # raises IOError: not opened for reading