Add --enable-static option to link icu4c libraries statically

.github/workflows/macos.yml

@@ -11,6 +11,11 @@ jobs:
       matrix:
         os: [macos]
         ruby: [ '3.2', '3.3' ]
+        compile_opt: [""]
+        include:
+          - os: "macos"
+            ruby: "3.3"
+            compile_opt: "ENABLE_STATIC=1"
 
     steps:
       - name: icu4c
@@ -23,5 +28,5 @@ jobs:
 
       - name: Install dependencies
         run: bundle install
-      - name: Run tests ${{ matrix.rubyopt }}
-        run: bundle exec rake RUBYOPT="${{ matrix.rubyopt }}"
+      - name: "Run tests with compile_opt: ${{ matrix.compile_opt }}, rubyopt: ${{ matrix.rubyopt }}"
+        run: ${{ matrix.compile_opt }} bundle exec rake RUBYOPT="${{ matrix.rubyopt }}"

Rakefile

@@ -11,6 +11,7 @@ require "rake/extensiontask"
 
 Rake::ExtensionTask.new 'charlock_holmes' do |ext|
   ext.lib_dir = File.join 'lib', 'charlock_holmes'
+  ext.config_options << '--enable-static' if ENV['ENABLE_STATIC']
 end
 
-Rake::Task[:test].prerequisites << :compile
+Rake::Task[:test].prerequisites << :compile

ext/charlock_holmes/extconf.rb

@@ -75,4 +75,67 @@
   end
 end
 
+def libflag_to_filename(ldflag)
+  case ldflag
+  when /\A-l(.+)/
+    "lib#{Regexp.last_match(1)}.#{$LIBEXT}"
+  end
+end
+
+def resolve_static_library(libflag, dirs)
+  filename = libflag_to_filename(libflag)
+
+  dir = dirs.find { |path| File.exist?(File.join(path, filename)) }
+
+  raise "Unable to find #{filename} in #{dirs}" unless dir
+
+  File.join(dir, filename)
+end
+
+def substitute_static_libs(packages)
+  packages.each do |pkg|
+    unless pkg_config(pkg)
+      message = <<~MSG
+        Unable to run `pkg-config #{pkg}`.
+
+        Check that PKG_CONFIG_PATH includes #{pkg}.pc (or unset it if it's already set).
+
+        Current environment:
+        PKG_CONFIG_PATH=#{ENV['PKG_CONFIG_PATH']}
+      MSG
+
+      raise message
+    end
+  end
+
+  # First, find all the -l<lib> flags added by pkg-config. We want to drop
+  # these dynamically linked libraries and substitute them with the static libraries.
+  libflags = packages.map do |pkg|
+    pkg_config(pkg, 'libs-only-l')&.strip&.split(' ')
+  end.flatten.uniq
+
+  # To find where the static libraries live, we need to search the
+  # library paths given by the -L flag from pkg-config.
+  lib_paths = packages.map do |pkg|
+    include_path = pkg_config(pkg, 'libs-only-L')&.strip
+    include_path&.split(' ')&.map { |lib| lib.gsub(/^-L/, '') }
+  end.flatten.uniq
+
+  # Drop the -l<lib> flags and add in the static libraries.
+  new_libs = $libs.shellsplit
+  new_libs.reject! { |arg| libflags.include?(arg) }
+  libflags.each { |flag| new_libs << resolve_static_library(flag, lib_paths) }
+  $libs = new_libs.uniq.shelljoin
+end
+
+static_p = enable_config('static', false)
+message "Static linking is #{static_p ? 'enabled' : 'disabled'}.\n"
+
+if static_p
+  $CXXFLAGS << ' -fPIC'
+  ENV['PKG_CONFIG_ALLOW_SYSTEM_LIBS'] = '1'
+
+  substitute_static_libs(%w[icu-i18n icu-io icu-uc])
+end
+
 create_makefile 'charlock_holmes/charlock_holmes'