test: try using ruby_memcheck to look for leaks

.github/workflows/ci.yml

@@ -296,3 +296,26 @@ jobs:
             bundle install --local || bundle install
             bundle exec rake compile -- --${{matrix.sys}}-system-libraries
             bundle exec rake test
+
+  memcheck:
+    continue-on-error: true # this is experimental!
+    strategy:
+      fail-fast: false
+      matrix:
+        sys: ["enable", "disable"]
+        ruby: ["3.0"]
+    runs-on: ubuntu-latest
+    container:
+      image: ghcr.io/sparklemotion/nokogiri-test:mri-${{matrix.ruby}}
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          submodules: true
+      - uses: actions/cache@v2
+        if: matrix.sys == 'disable'
+        with:
+          path: ports
+          key: ports-ubuntu-${{hashFiles('dependencies.yml', 'patches/**/*.patch')}}
+      - run: bundle install --local || bundle install
+      - run: bundle exec rake compile -- --${{matrix.sys}}-system-libraries
+      - run: bundle exec rake test:memcheck

Gemfile

@@ -1,3 +1,5 @@
 source "https://rubygems.org"
 
 gemspec
+
+gem "ruby_memcheck", git: "https://github.com/peterzhu2118/ruby_memcheck"

rakelib/test.rake

@@ -1,5 +1,14 @@
 require "rake/testtask"
 
+begin
+  require "ruby_memcheck"
+  valgrind_options = RubyMemcheck::Configuration::DEFAULT_VALGRIND_OPTIONS.dup
+  valgrind_options << "--gen-suppressions=all"
+  RubyMemcheck.config(binary_name: "nokogiri", valgrind_options: valgrind_options)
+rescue LoadError
+  warn "could not load ruby_memcheck"
+end
+
 #
 #  much of this was ripped out of hoe-debugging
 #
@@ -95,4 +104,10 @@ namespace "test" do
   LldbTestTask.new("lldb") do |t|
     nokogiri_test_task_configuration(t)
   end
+
+  if defined?(RubyMemcheck)
+    RubyMemcheck::TestTask.new("memcheck") do |t|
+      nokogiri_test_task_configuration(t)
+    end
+  end
 end

test/helper.rb

@@ -11,6 +11,10 @@
 #   - "stress" - run tests with GC.stress set to true
 # - NOKOGIRI_GC: read more in test/test_memory_leak.rb
 #
+
+# make sure we do one final major before the process exits (for valgrind)
+at_exit { GC.start(full_mark: true) } unless ::RUBY_PLATFORM == "java"
+
 require 'simplecov'
 SimpleCov.start do
   add_filter "/test/"