30 Jun 2020

Building Ruby on arm64 macOS

As part of my new computer project, I’ve been trying to compile Ruby for arm64-darwin20 from source. The bad news is that if you don’t do anything in particular, it won’t work:

compiling closure.c
closure.c:264:14: error: implicit declaration of function 'ffi_prep_closure' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    result = ffi_prep_closure(pcl, cif, callback, (void *)self);
1 error generated.
make[2]: *** [closure.o] Error 1
make[1]: *** [ext/fiddle/all] Error 2
make: *** [build-ext] Error 2

The good news is that it’s possible to get it to work anyway. If you use ruby-install, there are two steps. First, you need to remove libffi from the list of packages. Then, you need to pass a couple of flags to the install process.

It looks like the ruby-core team is already starting to merge explicit support for arm64, so hopefully it won’t be long before none of the extra flags need to be passed in at all.

I’ve already removed the libffi brew package from my fork, so you can build Ruby 2.7.1 and 2.6.6 like this:

git clone https://github.com/indirect/ruby-install.git
cd ruby-install
./bin/ruby-install ruby 2.7.1 -c -- --with-arch=arm64 CFLAGS=-DUSE_FFI_CLOSURE_ALLOC=1 
./bin/ruby-install ruby 2.6.6 -c -- --with-arch=arm64 CFLAGS=-DUSE_FFI_CLOSURE_ALLOC=1 

Assuming you’ve already followed the steps from yesterday to fix system Ruby and Homebrew, that should be all you need!

$ ~/.rubies/ruby-2.7.1/bin/ruby -v
ruby 2.7.1p83 (2020-03-31 revision a0c7c23c9c) [arm64-darwin20]
$ ~/.rubies/ruby-2.6.6/bin/ruby -v 
ruby 2.6.6p146 (2020-03-31 revision 67876) [arm64-darwin20]