From: eregontp@... Date: 2019-07-01T14:33:14+00:00 Subject: [ruby-core:93452] [Ruby master Feature#15940] Coerce symbols internal fstrings in UTF8 rather than ASCII to better share memory with string literals Issue #15940 has been updated by Eregon (Benoit Daloze). byroot (Jean Boussier) wrote: > You do want both constants to reference the same symbol. From what I gathered it was the whole reason behind the ASCII coercion. That makes sense, thanks for the explanation. US-ASCII is the natural subset for 7-bit characters, so it makes perfect sense to me that it's used for 7-bit symbols. UTF-8 is not, and is less precise than US-ASCII for that matter. At least performance-wise it shouldn't matter too much since the coderange will be CR_7BIT. I'm unsure, it seems a bit arbitrary to give "ascii" symbols a UTF-8 encoding. And many core methods return US-ASCII Strings and I would say that it is expected when they only return 7-bit characters. ---------------------------------------- Feature #15940: Coerce symbols internal fstrings in UTF8 rather than ASCII to better share memory with string literals https://bugs.ruby-lang.org/issues/15940#change-78999 * Author: byroot (Jean Boussier) * Status: Open * Priority: Normal * Assignee: * Target version: ---------------------------------------- Patch: https://github.com/ruby/ruby/pull/2242 It's not uncommon for symbols to have literal string counterparts, e.g. ```ruby class User attr_accessor :name def as_json { 'name' => name } end end ``` Since the default source encoding is UTF-8, and that symbols coerce their internal fstring to ASCII when possible, the above snippet will actually keep two instances of `"name"` in the fstring registry. One in ASCII, the other in UTF-8. Considering that UTF-8 is a strict superset of ASCII, storing the symbols fstrings as UTF-8 instead makes no significant difference, but allows in most cases to reuse the equivalent string literals. The only notable behavioral change is `Symbol#to_s`. Previously `:name.to_s.encoding` would be `#`. After this patch it's `#`. I can't foresee any significant compatibility impact of this change on existing code. However, there are several ruby specs asserting this behavior, but I don't know if they can be changed or not: https://github.com/ruby/spec/commit/a73a1c11f13590dccb975ba4348a04423c009453 If this specification is impossible to change, then we could consider changing the encoding of the String returned by `Symbol#to_s`, e.g in ruby pseudo code: ```ruby def to_s str = fstr.dup str.force_encoding(Encoding::ASCII) if str.ascii_only? str end ``` -- https://bugs.ruby-lang.org/ Unsubscribe: