From: usa@... Date: 2017-08-09T08:31:37+00:00 Subject: [ruby-core:82299] [Ruby trunk Bug#13239] Bug with "special exceptions" when they are thrown in context of a rescue clause. Issue #13239 has been updated by usa (Usaku NAKAMURA). Backport changed from 2.2: UNKNOWN, 2.3: REQUIRED, 2.4: DONE to 2.2: UNKNOWN, 2.3: DONE, 2.4: DONE ruby_2_3 r59538 merged revision(s) 57415,57474. ---------------------------------------- Bug #13239: Bug with "special exceptions" when they are thrown in context of a rescue clause. https://bugs.ruby-lang.org/issues/13239#change-66089 * Author: nvashchenko (Nikolay Vashchenko) * Status: Closed * Priority: Normal * Assignee: * Target version: * ruby -v: 2.4.x, 2.3.x, etc * Backport: 2.2: UNKNOWN, 2.3: DONE, 2.4: DONE ---------------------------------------- I've stumbled upon a case when ruby is supposed to throw "IOError: stream closed"(https://github.com/ruby/ruby/blob/trunk/thread.c#L4823) because there was a retained FD lock by another thread, but I'm was getting this instead of it: ``` RuntimeError: can't modify frozen IOError /home/vagrant/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/puma-3.6.2/lib/puma/server.rb:877:in `write' /home/vagrant/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/puma-3.6.2/lib/puma/server.rb:877:in `<<' /home/vagrant/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/puma-3.6.2/lib/puma/server.rb:877:in `stop' ``` I've done some digging and it appeared to a be a ruby bug with how such exceptions(so called "special exceptions") are handled. This exception is being frozen right after creation: https://github.com/ruby/ruby/blob/trunk/vm.c#L2078 but later, when it's thrown, it's being handled exactly as regular exception that is not frozen, which leads to a problem here: https://github.com/ruby/ruby/blob/trunk/eval.c#L511 - it is an attempt to assign the "#cause" attribute on it when it all happens inside a rescue clause, since the exception itself is frozen. I've created a script to reproduce it: ```ruby rd, wr = IO.pipe Thread.new do IO.select [rd] wr.close end begin raise 'any exception' rescue wr << 'A' end ``` It works with this ruby fork where I've added sleep for couple of seconds to imitate slow system call response, to keep the FD locked for a while and produce initial exception: https://github.com/ruby/ruby/blob/trunk/eval.c#L511 -- https://bugs.ruby-lang.org/ Unsubscribe: