From: Benoit Daloze <eregontp@...>
Date: 2018-12-10T14:07:07+01:00
Subject: [ruby-core:90404] Re: [Ruby trunk Feature#15393] Add compilation flags to freeze Array and Hash literals

Interesting code :)
But also inefficient of course, making extra copies (changing
identity) and allocations.
On Mon, Dec 10, 2018 at 1:55 AM <shyouhei@ruby-lang.org> wrote:
>
> Issue #15393 has been updated by shyouhei (Shyouhei Urabe).
>
>
> Off topic:
>
> Eregon (Benoit Daloze) wrote:
> > One alternative idea which would achieve a similar goal is having #deep_freeze on core types, and recognizing `{ 'a' => ['b', { 'c' => 'd' }] }.deep_freeze`.
> > This would be more general, since it would also work for freezing non-constant/non-literal data structures.
>
> Object#deep_freeze can be written without any extensions right now, like this: https://github.com/shyouhei/optdown/blob/master/lib/optdown/deeply_frozen.rb
> I heard this trick from @akr .
>
> ----------------------------------------
> Feature #15393: Add compilation flags to freeze Array and Hash literals
> https://bugs.ruby-lang.org/issues/15393#change-75509
>
> * Author: tenderlovemaking (Aaron Patterson)
> * Status: Open
> * Priority: Normal
> * Assignee:
> * Target version:
> ----------------------------------------
> Hi,
>
> I would like to add VM compilation options to freeze array and hash literals.  For example:
>
> ~~~ ruby
> frozen = RubyVM::InstructionSequence.compile(<<-eocode, __FILE__, nil, 0, frozen_string_literal: true, frozen_hash_and_array_literal: true)
>   { 'a' => ['b', { 'c' => 'd' }] }
> eocode
> puts frozen.disasm
> ~~~
>
> Output is:
>
> ~~~
> $ ./ruby thing.rb
> == disasm: #<ISeq:<compiled>@thing.rb:0 (0,0)-(0,34)> (catch: FALSE)
> 0000 putobject                    {"a"=>["b", {"c"=>"d"}]}
> 0002 leave
> ~~~
>
> Anything nested in the hash that can't be "frozen" will cause it to not be frozen.
>
> For example:
>
> ~~~ ruby
> not_frozen = RubyVM::InstructionSequence.compile(<<-eocode, __FILE__, nil, 0, frozen_string_literal: true, frozen_hash_and_array_literal: true)
>   { 'a' => some_method }
> eocode
> puts not_frozen.disasm
> ~~~
>
> Output:
>
> ~~~
> $ ./ruby thing.rb
> == disasm: #<ISeq:<compiled>@thing.rb:0 (0,0)-(0,24)> (catch: FALSE)
> 0000 putobject                    "a"
> 0002 putself
> 0003 opt_send_without_block       <callinfo!mid:some_method, argc:0, FCALL|VCALL|ARGS_SIMPLE>, <callcache>
> 0006 newhash                      2
> 0008 leave
> ~~~
>
> Eventually I would like to freeze array and hash literals in source code itself, but I think this is a good first step.
>
> The reason I want this feature is I think we can reduce some object allocations, and once Guilds are implemented, easily create immutable data.
>
> I've attached a patch that implements the above.
>
> (Also I think maybe "frozen_literals" would be a better name, but I don't want to imply that numbers or booleans are frozen too)
>
> Thanks!
>
> ---Files--------------------------------
> 0001-Add-compile-options-for-freezing-hash-and-array-lite.patch (6.14 KB)
>
>
> --
> https://bugs.ruby-lang.org/
>
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