From: Run Paint Run Run <redmine@...>
Date: 2010-11-11T05:26:01+09:00
Subject: [ruby-core:33132] [Ruby 1.9-Bug#4040][Open] SystemStackError with Hash[*a] for Large _a_

Bug #4040: SystemStackError with Hash[*a] for Large _a_
http://redmine.ruby-lang.org/issues/show/4040

Author: Run Paint Run Run
Status: Open, Priority: Low
Category: core
ruby -v: ruby 1.9.3dev (2010-11-09 trunk 29737) [x86_64-linux] 

I've been hesitating over whether to file a ticket about this, so please feel free to close if I've made the wrong choice.

I often use Hash[*array.flatten] in IRB to convert arrays of arrays into hashes. Today I noticed that if the array is big enough, this would raise a SystemStackError. Puzzled, I looked deeper. I assumed I was hitting the maximum number of arguments a method's argc can hold, but realised that the minimum size of the array needed to trigger this exception differed depending on whether I used IRB or not. So, presumably this is indeed exhausting the stack...

In IRB, the following is the minimal reproduction of this problem:

  Hash[*130648.times.map{ 1 }]; true

I haven't looked for the minimum value needed with `ruby -e`, but the following reproduces:

  ruby -e 'Hash[*1380888.times.map{ 1 }]'

I suppose this isn't technically a bug, but maybe it offers another argument for either #666 or an extension of #3131.


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