[ruby-core:112987] [Ruby master Bug#4040] SystemStackError with Hash[*a] for Large _a_

Issue #4040 has been updated by jeremyevans0 (Jeremy Evans).


Considering we fixed this issue for iseq and cfunc methods, probably the main reason to reject fixing this issue for the remaining method types is that doing so potentially lowers performance.  To try to counteract this, I've updated my pull request to include an optimization for bmethods that improves performance 38-59% for simple method calls, and up to 180% for method calls with keywords. Hopefully this increase in bmethod performance more than cancels out any performance decreases caused by the large argument splat handling.

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Bug #4040: SystemStackError with Hash[*a] for Large _a_
https://bugs.ruby-lang.org/issues/4040#change-102518

* Author: runpaint (Run Paint Run Run)
* Status: Open
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
* ruby -v: ruby 1.9.3dev (2010-11-09 trunk 29737) [x86_64-linux] 
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
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=begin
 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.
=end




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