Use ruby_memcheck in CI

Followed https://github.com/Shopify/ruby_memcheck#setup

.github/workflows/tests.yaml

@@ -176,3 +176,16 @@ jobs:
           Test outcome: ${{ steps.test.outcome }}
         # every step must define a `uses` or `run` key
         run: echo NOOP
+
+  valgrind:
+    runs-on: ubuntu-latest
+    env:
+      PUMA_RUBY_MEMCHECK: true
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: '3.0'
+          bundler-cache: true
+          apt-get: valgrind
+      - run: bundle exec rake test:valgrind

Gemfile

@@ -21,6 +21,10 @@ unless ENV['PUMA_NO_RUBOCOP'] || RUBY_PLATFORM.include?('mswin')
   gem 'rubocop-performance', require: false
 end
 
+if ENV['PUMA_RUBY_MEMCHECK'] && RUBY_PLATFORM.include?('linux')
+  gem "ruby_memcheck"
+end
+
 if RUBY_VERSION == '2.4.1'
   gem "stopgap_13632", "~> 1.0", :platforms => ["mri", "mingw", "x64_mingw"]
 end

Rakefile

@@ -104,6 +104,12 @@ namespace :test do
   desc "Run all tests"
 
   task :all => :test
+
+  if ENV['PUMA_RUBY_MEMCHECK'] && RUBY_PLATFORM.include?('linux')
+    require 'ruby_memcheck'
+    RubyMemcheck.config(binary_name: 'puma_http11')
+    RubyMemcheck::TestTask.new(valgrind: :compile)
+  end
 end
 
 task :default => [:rubocop, "test:all"]

test/helper.rb

@@ -188,6 +188,8 @@ def self.run(reporter, options = {}) # :nodoc:
   def full_name
     "#{self.class.name}##{name}"
   end
+
+  at_exit { GC.start }
 end
 
 Minitest.after_run do
@@ -205,6 +207,7 @@ def full_name
       end
     end
   end
+  GC.start
 end
 
 module AggregatedResults