Bug #20802: It is possible to set the encoding of an IO instance to one that requires binmode when binmode is not set

• Status: Open
• Assignee: -
• Target version: -
• ruby -v: ruby 3.3.4 (2024-07-09 revision be1089c8ec) [x86_64-linux]
• Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN

[javanthropus (Jeremy Bopp)]

I don't know what problems this may cause, but there are guards against setting the encoding of an IO instance to one such as UTF-16LE when the IO instance is not set to binary mode. Here is a method to bypass those guards:

f1 = File.open('/dev/null')
f2 = File.open('/dev/null')
f1.binmode
f1.set_encoding('utf-16le')
f2.set_encoding('utf-8')
f1.reopen(f2)

f1.binmode?            # <= false
f1.external_encoding   # <= Encoding::UTF_16LE

[javanthropus (Jeremy Bopp)]

• Description updated (diff)