From: ncopa@...
Date: 2018-06-11T12:22:35+00:00
Subject: [ruby-dev:50565] [Ruby trunk Bug#14387] Ruby 2.5 を Alpine Linux で実行すると比較的浅めで SystemStackError 例外になる

Issue #14387 has been updated by ncopa (Natanael Copa).


naruse (Yui NARUSE) wrote:
> jottr (jottr -) wrote:
> > I'd like to inquire on the progress of this issue. What is missing to get this resolved? 
> > 
> > It is affecting downstream users who deploy their ruby applications by means of alpine linux containers. The alpine linux ruby containers are currently unusable because of this.
> 
> get_stack and get_main_stack needs platform dependent implementation.
> In this context "platform" means libc (or libthread or something on some OSes).
> Therefore ncopa's patch looks good for me in general.
> 
> The blocker seems
> * ncopa's patch breaks non linux environment because the patch removes `define get_main_stack` but not defined for other thant Linux non glibc

No. `get_main_stack` gets defined in the #else block for everything that is not Linux or not glibc:
````
#if defined(__linux__) && !defined(__GLIBC__) && defined(HAVE_GETRLIMIT)
 ...
#else
# define get_main_stack(addr, size) get_stack(addr, size)
#endif
````

I can turn it around the other for better readability if you want:
````
#if !defined(__linux__) || defined(__GLIBC__) || !defined(HAVE_GETRLIMIT)
# define get_main_stack(addr, size) get_stack(addr, size)
#else
# ...
#endif
````

> * minor one: it should add comment about !defined(__GLIBC__) intends musl libc and uClibc defines __GLIBC__.

Will add comment about musl libc. I think uClibc behavior is irrelevant here.

----------------------------------------
Bug #14387: Ruby 2.5 を Alpine Linux で実行すると比較的浅めで SystemStackError 例外になる
https://bugs.ruby-lang.org/issues/14387#change-72465

* Author: koshigoe (Masataka SUZUKI)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-linux-musl]
* Backport: 2.3: DONTNEED, 2.4: DONTNEED, 2.5: REQUIRED
----------------------------------------
CircleCI で Alpine Linux を使って Ruby 2.5.0 で Rubocop を実行した時に遭遇した例外です(Ruby 2.4.3 では発生しませんでした)。

Ruby のバージョンによって、再帰が止められるまでの回数に大きな違いがあるのはなぜでしょうか？
これは、意図された挙動なのか、Ruby の変更によるものでは無く Alpine Linux 固有の問題なのか、教えていただく事は可能でしょうか？

Alpine Linux の Tread stack size が比較的小さい事で、Ruby 2.5.0 からこのような挙動になったのでしょうか？
https://wiki.musl-libc.org/functional-differences-from-glibc.html#Thread-stack-size

## 再現

問題の再現のため、以下の様な再帰するコードを実行します。

~~~ ruby
# test.rb
n = 100000
res = {}
1.upto(n).to_a.inject(res) do |r, i|
  r[i] = {}
end

def f(x)
  x.each_value { |v| f(v) }
end

f(res)
~~~

Ruby 2.4.3 で実行した場合、 10061 levels で例外があがりました。

~~~
% docker container run \
  -v (pwd):/mnt/my --rm \
  ruby:2.4.3-alpine3.7 \
  ruby -v /mnt/my/test.rb
ruby 2.4.3p205 (2017-12-14 revision 61247) [x86_64-linux-musl]
/mnt/my/test.rb:9:in `each_value': stack level too deep (SystemStackError)
        from /mnt/my/test.rb:9:in `f'
        from /mnt/my/test.rb:9:in `block in f'
        from /mnt/my/test.rb:9:in `each_value'
        from /mnt/my/test.rb:9:in `f'
        from /mnt/my/test.rb:9:in `block in f'
        from /mnt/my/test.rb:9:in `each_value'
        from /mnt/my/test.rb:9:in `f'
        from /mnt/my/test.rb:9:in `block in f'
         ... 10061 levels...
        from /mnt/my/test.rb:9:in `block in f'
        from /mnt/my/test.rb:9:in `each_value'
        from /mnt/my/test.rb:9:in `f'
        from /mnt/my/test.rb:12:in `<main>'
```

一方で Ruby 2.5.0 で実行した場合、 134 level で例外があがりました。

```
% docker container run \
  -v (pwd):/mnt/my --rm \
  test/ruby:trunk-alpine3.7 \
  ruby -v /mnt/my/test.rb
ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-linux-musl]
/mnt/my/test.rb:9:in `each_value': stack level too deep (SystemStackError)
        from /mnt/my/test.rb:9:in `f'
        from /mnt/my/test.rb:9:in `block in f'
        from /mnt/my/test.rb:9:in `each_value'
        from /mnt/my/test.rb:9:in `f'
        from /mnt/my/test.rb:9:in `block in f'
        from /mnt/my/test.rb:9:in `each_value'
        from /mnt/my/test.rb:9:in `f'
        from /mnt/my/test.rb:9:in `block in f'
         ... 134 levels...
        from /mnt/my/test.rb:9:in `block in f'
        from /mnt/my/test.rb:9:in `each_value'
        from /mnt/my/test.rb:9:in `f'
        from /mnt/my/test.rb:12:in `<main>'
```

また、Ruby trunk で実行した場合は 2.5.0 同等の結果になりました。

```
ruby 2.6.0dev (2018-01-24 trunk 62017) [x86_64-linux-musl]
/mnt/my/test.rb:9:in `each_value': stack level too deep (SystemStackError)
        from /mnt/my/test.rb:9:in `f'
        from /mnt/my/test.rb:9:in `block in f'
        from /mnt/my/test.rb:9:in `each_value'
        from /mnt/my/test.rb:9:in `f'
        from /mnt/my/test.rb:9:in `block in f'
        from /mnt/my/test.rb:9:in `each_value'
        from /mnt/my/test.rb:9:in `f'
        from /mnt/my/test.rb:9:in `block in f'
         ... 134 levels...
        from /mnt/my/test.rb:9:in `block in f'
        from /mnt/my/test.rb:9:in `each_value'
        from /mnt/my/test.rb:9:in `f'
        from /mnt/my/test.rb:12:in `<main>'
```

※ trunk の Docker イメージを作った際の Dockerfile は以下。
https://gist.github.com/koshigoe/509be02a3580cdfc7a2cc45a4e6e44c5


---Files--------------------------------
0001-thread_pthread.c-make-get_main_stack-portable-on-lin.patch (2.61 KB)


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