[ruby-core:53447] [ruby-trunk - Feature #7791] Let symbols be garbage collected

Issue #7791 has been updated by kstephens (Kurt  Stephens).


marcandre (Marc-Andre Lafortune) wrote:
> kstephens (Kurt  Stephens) wrote:
> > I'm considering creating a first-class struct RSymbol and making ID synonymous with VALUE
> 
> I might be mistaken, but wouldn't that be a problem because many external libraries assume, like MRI does, that rb_intern("*") == '*', and the same for '+', ... This would no longer be the case, right?

Yup.  That's an assumption I can't fix.  Unless we have a class of VALUES < 127 that are immediate single-ASCII character Symbols, and we cant do that because it will collide with other immediates.  Ugh.  More magic, lookup tables and special cases.  :(

I was gonna define CHAR2SYM(C) and SYM2CHAR(VALUE) for things like ID2SYM('+') in parse.y and elsewhere.

Are there really that many extensions that rely on rb_symbol("+") == '+', or switch stmts?  They should rb_intern("+") into a static ID (or VALUE!) variable, like most extensions.

IMO, ID/VALUE distinction and magic is an unnecessary abomination.

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Feature #7791: Let symbols be garbage collected
https://bugs.ruby-lang.org/issues/7791#change-37631

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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