How to install and run ffi on M1 Mac - ruby-on-rails

Question

I'm using 'ffi', '~> 1.9',
I'm getting this error when I try to run my rails project
rake aborted!
LoadError: dlopen(/Users/kanye.west/.rbenv/versions/2.6.9/lib/ruby/gems/2.6.0/gems/ffi-1.9.25/lib/ffi_c.bundle, 0x0009): tried: '/Users/kanye.west/.rbenv/versions/2.6.9/lib/ruby/gems/2.6.0/gems/ffi-1.9.25/lib/ffi_c.bundle' (mach-o file, but is an incompatible architecture (have (x86_64), need (arm64e))) - /Users/kanye.west/.rbenv/versions/2.6.9/lib/ruby/gems/2.6.0/gems/ffi-1.9.25/lib/ffi_c.bundle
/Users/kanye.west/dev/anenta/config/application.rb:14:in `<top (required)>'
/Users/kanye.west/dev/anenta/Rakefile:5:in `require'
/Users/kanye.west/dev/anenta/Rakefile:5:in `<top (required)>'
/Users/kanye.west/.rbenv/versions/2.6.9/bin/bundle:23:in `load'
/Users/kanye.west/.rbenv/versions/2.6.9/bin/bundle:23:in `<main>'
Caused by:
LoadError: cannot load such file -- 2.6/ffi_c
/Users/kanye.west/dev/anenta/config/application.rb:14:in `<top (required)>'
/Users/kanye.west/dev/anenta/Rakefile:5:in `require'
/Users/kanye.west/dev/anenta/Rakefile:5:in `<top (required)>'
/Users/kanye.west/.rbenv/versions/2.6.9/bin/bundle:23:in `load'
/Users/kanye.west/.rbenv/versions/2.6.9/bin/bundle:23:in `<main>'
(See full trace by running task with --trace)
Approaches tried
gem install --user-install ffi -v '1.9.25' -- --enable-libffi-alloc
gem install ffi -v '1.9.25' -- --with-cflags="-Wno-error=implicit-function-declaration"
gem install ffi -v '1.9.25' --platform=rub
alias gem="arch -x86_64 sudo gem"
CFLAGS="-Wno-error=implicit-function-declaration" RUBY_CONFIGURE_OPTS='--with-readline-dir=/opt/homebrew/opt/readline' gem install ffi -v '1.9.25' -- --with-cflags="-Wno-error=implicit-function-declaration"

Answer 1

You need to install libffi using homebrew:
brew install libffi
Then the installation should succeed with:
gem install ffi
I've tested this on ruby 2.7.2 on my m1.
Also make sure that both libffi and ruby/gem are running on the same architecture. You may have mixed some arm64 and x86 binaries which will lead to lots of compiler errors in the long run. If you encounter "wrong architecture" errors, try to reinstall ruby/homebrew on arm/m1.
For reference:
I'm using chruby installed through homebrew and installed ruby 2.7.2 via ruby-install.
Both homebrew and ruby are not using rosetta emulation and are compiled on arm64. I've installed libffi using brew install and then installed ffi using gem install without problems.
pascal#0xc0fefe ~> which ruby
/Users/pascal/.rubies/ruby-2.7.2/bin/ruby
pascal#0xc0fefe ~> which ruby-install
/opt/homebrew/bin/ruby-install
pascal#0xc0fefe ~> file /Users/pascal/.rubies/ruby-2.7.2/bin/ruby
/Users/pascal/.rubies/ruby-2.7.2/bin/ruby: Mach-O 64-bit executable arm64
pascal#0xc0fefe ~> gem install ffi
Building native extensions. This could take a while...
Successfully installed ffi-1.15.5
Parsing documentation for ffi-1.15.5
Done installing documentation for ffi after 0 seconds
1 gem installed

Answer 2

Here's the only workaround I found working, download Rosette, https://support.apple.com/en-us/HT211861, and uninstall (you need to do this in order for anything not compatible with the current architecture):
ruby versions
homebrew
rbenv
and select Get Info on Terminal, and check the Open using Rosetta.
Now reinstall
homebrew
rbenv
ruby
Run ruby -v
Check and verify that your version has ... [universal.x86_64-darwin21]

Answer 3

The thing is that official support for M1 was added in ffi v 1.14.0, so try update to that version, should not break anything.
gem uninstall ffi
and change manually in Gemfile.lock to 1.14.0.
gem install ffi -v '1.14.0'
This is what worked for me.

Answer 4

I've been trying to install a demo React Native App that innocently asked to run pod install and the went down this ffi rabbit hole.
On my M2 / Monterey, this article worked well except it was missing the instruction to install the ruby plugin for asdf
asdf plugin add ruby https://github.com/asdf-vm/asdf-ruby.git