How to rebuild old ruby on modern macos, because of course the headers moved and bundler suddenly can't build native extensions any more

Ruby 1.8.7 ree-187 macOS Catalina 10.15.7.sh

# This is based on https://gist.github.com/whitehat101/87c06c29dabfe15f094ec331b77a7c6d and https://solitum.net/openssl-os-x-el-capitan-and-brew/
# I take no responsibility for the damage it may do to any other build system you run.

# Disable system integrity protection before this mess.


# Uninstall everything critical to get back to baseline

rbenv uninstall ree-1.8.7-2012.02

# also make sure any old versions of openssl and gcc you have installed thru brew are uninstalled

# make sure you have all this crap installed, even though the build may not touch some of these
brew install openssl libyaml libffi readline libxml2

# reinstall gcc
brew install gcc@6

# upgrade ruby-build, which you probably have already and may be the problem, this is a rats' nest
brew upgrade ruby-build

# install old openssl 0.9.8 because who cares about safety or anything, this is a development environment and we need old headers
# brew install https://github.com/Homebrew/homebrew-versions/raw/586b7e9012a3ed1f9df6c43d0483c65549349289/openssl098.rb
# Homebrew is now very grouchy about installing random formulae from github urls, so here's some additional rigamarole:
brew tap-new oldssl/openssl098
curl -L https://raw.githubusercontent.com/Homebrew/homebrew-cask-versions/586b7e9012a3ed1f9df6c43d0483c65549349289/openssl098.rb -o /usr/local/Homebrew/Library/Taps/oldssl/homebrew-openssl098/Formula/openssl098.rb
sed -i '' 's/MacOS\.prefer_64_bit\?/Hardware\:\:CPU\.is_64_bit\?/g' /usr/local/Homebrew/Library/Taps/oldssl/homebrew-openssl098/Formula/openssl098.rb
sed -i '' 's/by_osx/by_macos/g' /usr/local/Homebrew/Library/Taps/oldssl/homebrew-openssl098/Formula/openssl098.rb
brew style --fix /usr/local/Homebrew/Library/Taps/oldssl/homebrew-openssl098/Formula/openssl098.rb
brew install --build-from-source openssl098

# # Un-comment out the below two commands if this script doesn't work the first time.
# # You're gonna take yourself right into the danger zone with this one. Symlink the old openssl headers into your lib. 
# # Rbenv install doesn't always honor ldflags for some reason (we will use them anyway later)
# cd /usr/local/include
# ln -s ../opt/openssl098/include/openssl .

# install ree-187
CC=gcc-6 \
CFLAGS="-O2 -fno-tree-dce -fno-optimize-sibling-calls -I/usr/local/Cellar/openssl098/0.9.8zh/include -I/usr/local/opt/libxml2/include" \
CPPFLAGS="-I/usr/local/opt/libxml2/include" \
LDFLAGS="-L/usr/local/Cellar/openssl098/0.9.8zh/lib -L/usr/local/opt/libxml2/lib" \
rbenv install ree-1.8.7-2012.02

# make sure we're in the right ruby to test/install stuff
rbenv shell ree-1.8.7-2012.02

# the following should output "OK"; if it doesn't, you need to go into the danger zone (above)
ruby -ropenssl -e "puts :OK"

# install core gems that are old enough to work with this version of ruby
gem install rdoc -v 4.2.0
gem install rdoc-data
rbenv rehash
rdoc-data --install
gem install builder -v 3.2.3
gem install bundler -v 1.16.2
bundle config build.nokogiri --use-system-libraries --with-xml2-include=$(brew --prefix libxml2)/include/libxml2
bundle config build.mysql --with-opt-lib=/usr/local/Cellar/openssl098/0.9.8zh/lib


# This worked for me. Builds native extensions again and everything. Will it work for you? Let's hope so. If not? Too bad.

Ruby 1.8.7 ree-187 macOS Sierra 10.12.3

# This is based on https://gist.github.com/whitehat101/87c06c29dabfe15f094ec331b77a7c6d and https://solitum.net/openssl-os-x-el-capitan-and-brew/
# I take no responsibility for the damage it may do to any other build system you run.

# Uninstall everything critical to get back to baseline

brew remove apple-gcc42
rbenv uninstall ree-1.8.7-2012.02
# also make sure any old versions of openssl you have installed thru brew are uninstalled

# make sure you have all this crap installed, even though the build may not touch some of these
brew install openssl libyaml libffi readline

# reinstall gcc-42
brew tap homebrew/dupes && brew install apple-gcc42

# upgrade ruby-build, which you probably have already and may be the problem, this is a rats' nest
brew upgrade ruby-build

# install old openssl 0.9.8 because who cares about safety or anything, this is a development environment and we need old headers
brew install https://github.com/Homebrew/homebrew-versions/raw/586b7e9012a3ed1f9df6c43d0483c65549349289/openssl098.rb

# take yourself right into the danger zone with this one. Symlink the old openssl headers into your lib. 
# Rbenv install doesn't always honor ldflags for some reason (we will use them anyway later)
cd /usr/local/include
ln -s ../opt/openssl098/include/openssl .

# install ree-187
LDFLAGS="-L/usr/local/opt/openssl098/lib" CPPFLAGS="-I/usr/local/opt/openssl098/include" PKG_CONFIG_PATH="/usr/local/opt/openssl098/lib/pkgconfig" RUBY_CONFIGURE_OPTS=--with-readline-dir="$(brew --prefix readline)" rbenv install 1.8.7-p352

# install a version of bundler that works with antique Gemfiles, but modern enough for rack-reverse-proxy-0.11.0 [bundler (~> 1.7)]
gem install bundler -v 1.7.15 

# This worked for me. Builds native extensions again and everything. Will it work for you? Let's hope so. If not? Too bad.

Here's an addendum. I haven't rebuilt anything in catalina yet, since the sierra build seems to work still.

But, you're gonna need new openssl root certs to connect to rubygems et al.

cd /usr/local/etc/openssl
curl -OL http://curl.haxx.se/ca/cacert.pem
mv cacert.pem cert.pem

Installing from a local formula does not require manifests (which don't exist) to be downloaded:

brew install --build-from-source /usr/local/Homebrew/Library/Taps/oldssl/homebrew-openssl098/openssl098.rb

@schmijos are you running that command in lieu of line 29 of the Catalina script above? That full path causes brew to return Error: No available formula or cask with the name "/usr/local/Homebrew/Library/Taps/oldssl/homebrew-openssl098/openssl098.rb". for me. However, you are right that the build from source flag will keep brew from needlessly hitting bintray for something that no longer exists.

I have updated the script to take that into account. Thanks so much!

Oh, yes. I guess I forgot Formula in the file path 🙈