From: nobu@...
Date: 2018-09-21T08:36:26+00:00
Subject: [ruby-core:89119] [Ruby trunk Bug#14959] Writing a "link_to" method and a "url_helper" with a request parameter under certain "if else" statement in Rails helper crashes with KERN_INVALID_ADDRESS at 0x0000000000000000

Issue #14959 has been updated by nobu (Nobuyoshi Nakada).


The same issue is already marked to backport in #14897.
Please wait for 2.5.2.

----------------------------------------
Bug #14959: Writing a "link_to" method and a "url_helper" with a request parameter under certain "if else" statement in Rails helper crashes with KERN_INVALID_ADDRESS at 0x0000000000000000
https://bugs.ruby-lang.org/issues/14959#change-74138

* Author: y4m4p (Masahiro Yamashita)
* Status: Closed
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-darwin14]
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
----------------------------------------
# Disclaimer 
Sorry about the problem being rails, and not ruby specific. I couldn't narrow down the problem and wording it correctly.
As it turns out that the problem derived from the ruby vm used in my Rails application, I decided to create the issue here.

## Backstory
I have created this issue in rails/rails. (https://github.com/rails/rails/issues/33460)
I became aware that this issue derives from Shopify/bootsnap (https://github.com/Shopify/bootsnap/issues/182)
The member there told me that this is an issue with the ruby vm itself, so I have created this issue here.

Please refer for more information in the above link.

# Reproduction
## Reproduction Project:
https://github.com/y4m4p/rails_issue_33460

## Project Dependency
program	version
ruby	        2.5.1p57 (2018-03-29 revision 63029) [x86_64-darwin17]
Rails	5.2.0
Bundler	1.16.1
Mysql	5.7.21 Homebrew

## Reproduction method
~~~ ruby
def helper_method
  if true
    link_to 'page', some_view_path(foo: 'true')
  else
    link_to 'somewhere', some_view_path(foo: 'false')
  end
end
~~~

### Crash condition
Writing this helper method under "app/helper" directory in Rails which satisfies all of the next particular conditions will crash the Rails server application with 
KERN_INVALID_ADDRESS at 0x0000000000000000.

* Writing a condition with
~~~ ruby
if true 
  ... 
else 
  ...
~~~
OR
~~~ ruby
if false 
  ... 
else 
  ...
~~~

* Write a path using the "link_to" helper and a "url_helper (xxx_path)" which contains a "request parameter" (xxx_path(some_parameter: 'x')).
* Writing the process under the statement that will never be used. 
For example, if you write the "if" sentence with "if true" then you must write your process under the "else" statement and vice versa.


### Non crashing condition
* Writing the "if" condition with a instance variable or constant. 
~~~ ruby
def helper_method
  condition = true
  if condition
    ...
  else
    ...
  end
end
~~~

* Do not write the specific "link_to" helper process under the statement that will never be used.
~~~ ruby
def helper_method
  if true
    link_to 'somewhere', web_pages_some_view_path(foo: 'true')
  else
    # link_to 'somewhere', web_pages_some_view_path(foo: 'false')  <= comment out
  end
end
~~~

* Do not write the request parameter for the "url_helper" path.
~~~ ruby
def helper_method
  if true
    link_to 'somewhere', web_pages_some_view_path(foo: 'true') #<= Writing the request parameter in the used statement is OK
  else
    link_to 'somewhere', web_pages_some_other_view_path
  end
end
~~~
* Do not write the process in helper. But rather, writing the process in the view itself will not crash.
~~~ ruby
# app/view/web_pages/some_view.html.erb
<%=  if true
       link_to 'somewhere', web_pages_some_view_path(foo: 'true')
      else
        link_to 'somewhere', web_pages_some_view_path(foo: 'false')
      end %>
~~~
 
## Expected
Should render correct views with link and not crash.
Even though I am writing the "if" condition with "true" which makes the "else" statement useless, but this should work as intended. (Just render the "true" statement.)

---Files--------------------------------
ruby_2018-08-03-030208_y4m4p.crash (63.6 KB)


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