From: Eric Wong <normalperson@...>
Date: 2017-08-30T19:29:24+00:00
Subject: [ruby-core:82539] Re: [Ruby trunk Bug#13851] getting "can't modify string; temporarily locked" on non-frozen instances

cardoso_tiago@hotmail.com wrote:
> I can't unfortunately reproduce this in a deterministic way. I
> can only say that the `read` routine is called in multiple
> threads (different io's instances of that class). The errors
> come seldom, however.

That's not good, and reading prelude.rb, io.c and string.c; I'm
not seeing how it's possible unless you have accidental sharing
going on.  Can you reproduce the problem with 2.4 or trunk?

Even if not deterministic, can you write a standalone infinite
loop which can eventually reproduce this?

Another option may be to try thread-local storage for @buffer,
instead, if you never need the data long-term.  IME, it will
save memory for C10K situations and help avoid accidental
sharing bugs (if indeed your fault :)

> I'm running ruby 2.3.4, and the frozen string literal is
> activated for the file where the class is defined. I first
> assumed that it was the buffer, but due to its initialization,
> it should be marken as not-frozen. 

Right, I'm not seeing this, either...

Btw, I prefer to use (since Ruby 2.0+):

	@buffer = ''.b

Rather than:

	@buffer = String.new("", encoding: Encoding::BINARY)

...in your situation, as it is much shorter :)

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