From: "alexeymuranov (Alexey Muranov)" <redmine@...>
Date: 2013-02-27T04:21:30+09:00
Subject: [ruby-core:52953] [ruby-trunk - Feature #7791] Let symbols be garbage collected


Issue #7791 has been updated by alexeymuranov (Alexey Muranov).


=begin
How about adding a new class between (({Symbol})) and (({String})) instead of garbage collecting symbols?  Something like (({StaticString})) with a special literal notation, like

  `"There exist only one copy of this string"("utf-8")  # a static string in UTF-8 encoding

  `this_is_also_unique                         # in the default encoding

  `"the 3rd letter of this string is"[3]       # => "e"

  `'this is unique!'.equal? `'this is unique!' # => true
They would be indexed and garbage collected constant strings.  Using the same literal twice would actually use the same object.

Other alternatives for the literal notation: (({\"This is static!"})),  (({|"This is static!"})), (({%S"This is static!"})).
=end

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Feature #7791: Let symbols be garbage collected
https://bugs.ruby-lang.org/issues/7791#change-37112

Author: rosenfeld (Rodrigo Rosenfeld Rosas)
Status: Feedback
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: next minor


Lots of Denial-of-Service security vulnerabilities exploited in Ruby programs rely on symbols not being collected by garbage collector.

Ideally I'd prefer symbols and strings to behave exactly the same being just alternate ways of writing strings but I'll let this to another ticket.

This one simply asks for symbols to be allowed to be garbage collected when low on memory. Maybe one could set up some up-limit memory constraints dedicated to storing symbols. That way, the most accessed symbols would remain in that memory region and the least used ones would be reclaimed when the memory for symbols is over and a new symbol is created.

Or you could just allow symbols to be garbage collected any time. Any reasons why this would be a bad idea? Any performance benchmark demonstrating how using symbols instead of strings would make a real-world software perform much better?

Currently I only see symbols slowing down processing because people don't want to worry about it and will often use something like ActiveSupport Hash#with_indifferent_access or some other method to convert a string to symbol or vice versa...


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