Add Valgrind memcheck (ruby_memcheck) for the C extension

Gemfile

@@ -2,3 +2,5 @@ source 'https://rubygems.org'
 
 # Specify your gem's dependencies in zstd_ruby.gemspec
 gemspec
+
+gem 'ruby_memcheck', '~> 3.0' if RUBY_PLATFORM.include?('linux')

Rakefile

@@ -15,6 +15,34 @@ end
 
 task :default => [:clobber, :compile, :spec]
 
+if RUBY_PLATFORM.include?('linux')
+  begin
+    require 'ruby_memcheck'
+    require 'ruby_memcheck/rspec/rake_task'
+
+    RubyMemcheck.config(
+      binary_name: 'zstdruby',
+      # Valgrind and YJIT interfere with each other, adding noise and slowdown,
+      # so keep YJIT disabled while running under Valgrind.
+      ruby: "#{FileUtils::RUBY} --disable-yjit"
+    )
+
+    namespace :spec do
+      task :check_valgrind do
+        unless system('command -v valgrind > /dev/null 2>&1')
+          abort("\nValgrind is required for `rake spec:valgrind` but was not found.\n" \
+                "Install it first (Linux only), e.g. `sudo apt-get install valgrind`.\n")
+        end
+      end
+
+      RubyMemcheck::RSpec::RakeTask.new(valgrind: [:check_valgrind, :compile])
+    end
+  rescue LoadError
+    # ruby_memcheck is an optional, Linux-only development dependency. If it is
+    # not installed just skip defining the task instead of breaking the Rakefile.
+  end
+end
+
 desc 'Sync zstd libs dirs to ext/zstdruby/libzstd'
 task :zstd_update do
   FileUtils.rm_r("ext/zstdruby/libzstd")