Issue #7791 has been updated by marcandre (Marc-Andre Lafortune).


kstephens (Kurt  Stephens) wrote:
> 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. 

Wouldn't it be safe to do this in ID2SYM though? I.e. keep the distinction between ID and VALUE, where in most case they are equal, but there's a mapping for a few special IDs < 127?

> 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.

You're right, they should. I was horrified the first time I realized that '+' was used as the ID for the :+ symbol!

I double checked Rubinius and that magic relation does not hold. In particular:

#define ID2SYM(id)        (id)

So it's probably only MRI that does stuff like `rb_funcall(obj, '>', 1, INT2FIX(0))`

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Feature #7791: Let symbols be garbage collected
https://bugs.ruby-lang.org/issues/7791#change-37642

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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