From: shugo@...
Date: 2015-12-16T01:42:12+00:00
Subject: [ruby-core:72166] [Ruby trunk - Bug #11811] Chaining lazy enumerators causes duplicate ouput

Issue #11811 has been updated by Shugo Maeda.

File vm_caller_setup_arg_block.diff added

Yusuke Endoh wrote:
> So I guess this is caused by nobu's optimization.

The bug was introduced in r51995:

```
Author: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date:   Thu Oct 1 10:52:52 2015 +0000

    vm_args.c: fix marking symbol ifunc
    
    * vm_args.c (vm_caller_setup_arg_block): store new ifunc for
      symbol in control frame proc to be marked.
    
    * proc.c (proc_new), vm_insnhelper.c (vm_yield_with_cfunc):
      block->proc may be an ifunc now.
```

It seems to be fixed by the attached patch, but I'm not sure.
Could you check it, nobu?


----------------------------------------
Bug #11811: Chaining lazy enumerators causes duplicate ouput
https://bugs.ruby-lang.org/issues/11811#change-55577

* Author: Chris Beer
* Status: Open
* Priority: Normal
* Assignee: Nobuyoshi Nakada
* ruby -v: ruby 2.3.0preview2 (2015-12-11 trunk 53028) [x86_64-darwin15]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
In Ruby 2.3.0-preview2, I'm seeing a change in behavior using lazy enumerators with select/reject and the & operator:

irb(main):037:0> %w(1 2 3).lazy.reject(&:empty?).each { |x| puts x }
1
1
2
2
3
3

Note that the output is doubled. However, if I don't use the & shorthand, the output is as expected:


irb(main):038:0> %w(1 2 3).lazy.reject { |x| x.empty? }.each { |x| puts x }
1
2
3
=> nil


And in Ruby 2.2.3, both variants produced the same result:

irb(main):001:0> %w(1 2 3).lazy.reject(&:empty?).each { |x| puts x }
1
2
3
=> nil


---Files--------------------------------
vm_caller_setup_arg_block.diff (1.03 KB)


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