compat: address "old-style-definition" compiler error on Ruby 3.1+

.github/workflows/build.yml

@@ -0,0 +1,31 @@
+name: Build
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ${{ matrix.runner }}
+    name: Ruby ${{ matrix.ruby }}/${{ matrix.runner }}
+    strategy:
+      matrix:
+        ruby:  ['2.7', '3.0', '3.1', '3.2', '3.3']
+        runner: [ubuntu-latest, macos-latest]
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby }}
+        bundler-cache: true
+
+    - name: Compile extension
+      run: |
+        bundle exec rake compile
+
+    - name: Run tests
+      run: |
+        bundle exec rake test

Rakefile

@@ -2,7 +2,7 @@ require "bundler/gem_tasks"
 require "rake/testtask"
 require 'rake/extensiontask'
 
-Rake::ExtensionTask.new("visibility_monitor_c")
+Rake::ExtensionTask.new("visibility_monitor")
 
 Rake::TestTask.new(test: :compile) do |t|
   t.libs << "test"

ext/visibility_monitor/extconf.rb

@@ -0,0 +1,5 @@
+require "mkmf"
+
+$CFLAGS << " -Wall -Werror"
+
+create_makefile "visibility_monitor"

ext/visibility_monitor/mkmf.log

@@ -0,0 +1,7 @@
+extconf.h is:
+/* begin */
+1: #ifndef EXTCONF_H
+2: #define EXTCONF_H
+3: #endif
+/* end */
+

ext/visibility_monitor_c/ext.c → ext/visibility_monitor/visibility_monitor.c

@@ -36,7 +36,7 @@ static VALUE monitor_set_visibility_placeholder(VALUE mod, VALUE method_name, VA
     return Qnil;
 }
 
-void Init_visibility_monitor_c() {
+void Init_visibility_monitor(void) {
     VALUE mVisibilityMonitor = rb_define_module("VisibilityMonitor");
 
     rb_define_method(mVisibilityMonitor, "public", monitor_public, -1);

visibility_monitor.gemspec

@@ -13,16 +13,16 @@ Gem::Specification.new do |spec|
   spec.homepage      = "https://github.com/dylanahsmith/visibility_monitor"
   spec.license       = "MIT"
 
-  spec.extensions    = ['ext/visibility_monitor_c/extconf.rb']
+  spec.extensions    = ['ext/visibility_monitor/extconf.rb']
   spec.files         = `git ls-files -z`.split("\x0").reject do |f|
     f.match(%r{^(test|spec|features)/})
   end
   spec.bindir        = "exe"
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
-  spec.add_development_dependency "bundler", "~> 1.16"
-  spec.add_development_dependency "rake", "~> 10.0"
-  spec.add_development_dependency "rake-compiler", "~> 1.0"
+  spec.add_development_dependency "bundler"
+  spec.add_development_dependency "rake"
+  spec.add_development_dependency "rake-compiler"
   spec.add_development_dependency "minitest", "~> 5.0"
 end