We encountered a rare issue the other day when deploying one of our Ruby on Rails 5 applications. Our deployments suddenly started failing with a massive 1600 lines of Ruby level backtrace information!

Here is an excerpt from our error log:

```
/usr/local/bundle/gems/ffi-1.11.1/lib/ffi/library.rb:112: [BUG] Illegal instruction at 0x00007f614aa991a5
ruby 2.6.5p114 (2019-10-01 revision 67812) [x86_64-linux-musl]
-- Control frame information -----------------------------------------------
c:0120 p:---- s:0685 e:000684 CFUNC  :open
c:0119 p:0022 s:0679 e:000678 BLOCK  /usr/local/bundle/gems/ffi-1.11.1/lib/ffi/library.rb:112 [FINISH]
c:0118 p:---- s:0670 e:000669 CFUNC  :each
c:0117 p:0113 s:0666 e:000665 BLOCK  /usr/local/bundle/gems/ffi-1.11.1/lib/ffi/library.rb:109 [FINISH]
c:0116 p:---- s:0659 e:000658 CFUNC  :map
c:0115 p:0069 s:0655 e:000654 METHOD /usr/local/bundle/gems/ffi-1.11.1/lib/ffi/library.rb:99
c:0114 p:0079 s:0648 e:000647 CLASS  /usr/local/bundle/gems/sassc-2.2.1/lib/sassc/native.rb:11
c:0113 p:0007 s:0644 e:000643 CLASS  /usr/local/bundle/gems/sassc-2.2.1/lib/sassc/native.rb:6
c:0112 p:0014 s:0641 e:000640 TOP    /usr/local/bundle/gems/sassc-2.2.1/lib/sassc/native.rb:5 [FINISH]
...
[NOTE]
You may have encountered a bug in the Ruby interpreter or extension libraries.
Bug reports are welcome.
For details: https://www.ruby-lang.org/bugreport.html
Aborted (core dumped)
```

A crew member eventually discovered [issue #146](https://github.com/sass/sassc-ruby/issues/146 "SassC-Ruby Issue #146") in the [sassc-ruby](https://rubygems.org/gems/sassc "SassC-Ruby Gem") project which was caused by the precompiled gem no longer being portable between different processor architectures.

This is a particular problem for us in this project because we use AWS CodeBuild to build our rails app docker image, which is then deployed to ECS.

### The Solution

Until this is resolved in the sassc-ruby project we have added the following to our Dockerfile before our bundle install:

```
RUN bundle config --local build.sassc --disable-march-tune-native
```

And now we can resume happy deployments!

* * *

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