From: eregontp@... Date: 2019-07-01T17:25:36+00:00 Subject: [ruby-core:93458] [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: > What do you mean by performance ? String comparisons ? If so it doesn't really matter much for symbols AFAIK. I mean performance of String operations on a UTF-8 vs a US-ASCII String. As @nirvdrum said above, some optimizations might only apply to US-ASCII, although in most cases the coderange should make it apply to UTF-8 too. > IMO there's two arguments here: > - Consistency / Least surprise: UTF-8 is now the default source file encoding, it would make sense that the symbols created out of these files (not just `Symbol` instances, but module names, method names etc) would be UTF-8 as well. Right, that argument makes sense to me. Does this PR also addresses module and method names? FWIW, TruffleRuby already uses UTF-8 for module and method names, and it seems not to be a compatibility problem. It will be a bit weird if there is a magic encoding comment though, as then Symbols, module/method names will be UTF-8 if 7-bit but the specified magic encoding if not 7-bit. ---------------------------------------- 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-79005 * 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: