Issue #19108 has been updated by matz (Yukihiro Matsumoto). Template strings should be ASCII compatible, exceptions otherwise. Matz. ---------------------------------------- Bug #19108: Format routines like pack blindly treat a string as ASCII-encoded https://bugs.ruby-lang.org/issues/19108#change-100391 * Author: chrisseaton (Chris Seaton) * Status: Open * Priority: Normal * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN ---------------------------------------- Format routines like pack and unpack blindly treat a string as ASCII-encoded, even if they aren't ASCII or ASCII-compatible. I tried to construct code that was misleading using ASCII-incompatible-encodings but couldn't do it in practice (no ASCII-incompatible encodings have a pack directive ASCII byte that is encoded as a printable character.) But I could demonstrate at least some strange behaviour: ``` p ['foo'].pack('u').encoding # => #<Encoding:US-ASCII> p ['foo'].pack('u'.encode('UTF-32BE')).encoding # => #<Encoding:ASCII-8BIT> ``` This is because the NUL characters in the second one (which aren't really NUL characters - they're part of the directive characters) explicitly trigger the encoding to change to binary. There is a warning, but the warning is only for unexpected directives. How about disallowing or warning for non-ascii compatible format strings? -- https://bugs.ruby-lang.org/