Bug #21658: Encoding objects are dumped with an encoding of US-ASCII

• Status: Rejected
• Assignee: -
• Target version: -
• ruby -v: ruby 3.4.7 (2025-10-08 revision 7a5688e2a2) +PRISM [arm64-darwin24]
• Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN

[headius (Charles Nutter)]

All encodings get Marshal.dump'ed with an encoding instance variable:

$ cx ruby-3.4 ruby -e 'Encoding.constants.each { p Marshal.dump(Encoding.const_get(it)) }'
"\x04\bIu:\rEncoding\x10MacJapanese\x06:\x06EF"
"\x04\bIu:\rEncoding\x10MacJapanese\x06:\x06EF"
"\x04\bIu:\rEncoding\rUS-ASCII\x06:\x06EF"
"\x04\bIu:\rEncoding\rUS-ASCII\x06:\x06EF"
"\x04\bIu:\rEncoding\x10MacJapanese\x06:\x06EF"
"\x04\bIu:\rEncoding\nUTF-7\x06:\x06EF"
"\x04\bIu:\rEncoding\nUTF-8\x06:\x06EF"
"\x04\bIu:\rEncoding\nUTF-7\x06:\x06EF"
...

This despite the fact that an Encoding does not have an encoding:

$ cx ruby-3.4 ruby -e 'Encoding::UTF_8.encoding'                                          
-e:1:in '<main>': undefined method 'encoding' for an instance of Encoding (NoMethodError)

Compare with JRuby output:

$ cx jruby-10.0.2.0 ruby -e 'p Marshal.dump(Encoding::UTF_8)'
"\x04\bu:\rEncoding\nUTF-8"

This extra instance variable data causes the output to be unloadable by JRuby, because an Encoding object cannot itself have an encoding:

$ cx jruby-10.0.2.0 ruby -e 'p Marshal.load("\x04\bIu:\rEncoding\nUTF-8\x06:\x06EF")' 
ArgumentError: UTF-8is not enc_capable
    load at org/jruby/RubyMarshal.java:165
  <main> at -e:1

This is reported as a JRuby issue here: https://github.com/jruby/jruby/issues/9050

Encoding should not marshal with an encoding it does not actually have.

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Rejected

That is not an instance variable of an Encoding instance, but the instance variable for the encoding of the name.