When running ruby-install, it fails to build. This also reported in rbenv issues (https://github.com/rbenv/ruby-build/issues/1725).
for example when installing ruby 2.6.8
# installing via ruby-install ( https://github.com/postmodern/ruby-install )
ruby-install ruby 2.6.8
it results in the following error
ossl_x509store.c:452:30: note: ')' token is here
result = rb_funcall(ctx, rb_intern("verify"), 0);
^~~~~~~~~~~~~~~~~~~
../.././include/ruby/ruby.h:1826:56: note: expanded from macro 'rb_intern'
__extension__ (RUBY_CONST_ID_CACHE((ID), (str))) : \
^
../.././include/ruby/ruby.h:2602:20: note: expanded from macro 'rb_funcall'
rb_funcallv(recv, mid, \
^~~
6 warnings generated.
linking shared-object openssl.bundle
installing default openssl libraries
make[2]: Leaving directory '/Users/xxxxx/src/ruby-2.6.8/ext/openssl'
make[2]: Entering directory '/Users/xxxxx/src/ruby-2.6.8/ext/ripper'
extracting ripper.y from ../.././parse.y
compiling compiler ripper.y
ripper.y:762.9-16: syntax error, unexpected identifier, expecting string
make[2]: *** [Makefile:332: ripper.c] Error 1
make[2]: Leaving directory '/Users/xxxxx/src/ruby-2.6.8/ext/ripper'
make[1]: *** [exts.mk:257: ext/ripper/all] Error 2
make[1]: Leaving directory '/Users/xxxxx/src/ruby-2.6.8'
make: *** [uncommon.mk:286: build-ext] Error 2
!!! Compiling ruby 2.6.8 failed!
Seems to be a compiler issue. First ensure that Xcode is installed appropriately. In my case, I had it installed already but you can opt to reinstall to be sure. hope this helps people save time trying to figure out the issue as compiling it takes several minutes.
# check xcode, should yield : /Library/Developer/CommandLineTools
xcode-select -p
# check xcode, should yield : xcode-select version 2384
xcode-select -v
# install xcode-select
xcode-select --install
# reinstall openssl and version 3
brew reinstall openssl@1.1
# install build dependancies
brew install openssl readline libyaml zlib bison bison@2.7
# ensure build is using bison
export PATH="$(brew --prefix bison@2.7)/bin:$PATH"
# set ruby compilation flags
export CFLAGS="-Wno-error=implicit-function-declaration"
export RUBY_CONFIGURE_OPTS="--with-openssl-dir=$(brew --prefix openssl@1.1) --with-readline-dir=$(brew --prefix readline) --with-libyaml-dir=$(brew --prefix libyaml) --with-zlib-dir=$(brew --prefix zlib)"
# install ruby via ruby-install
ruby-install ruby 2.6.8
a couple more steps if it fails
# ensure that openssl is linked
brew unlink openssl && brew link openssl --force
# load openssl 1.1 for compilation
export LDFLAGS="-L/opt/homebrew/opt/openssl@1.1/lib"
export CPPFLAGS="-I/opt/homebrew/opt/openssl@1.1/include"
export PKG_CONFIG_PATH="/opt/homebrew/opt/openssl@1.1/lib/pkgconfig"
# install ruby via ruby-install
ruby-install ruby 2.7.7