Support installing the gem on TruffleRuby

* Fixes #159

.github/workflows/ci.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [ ruby-head, '3.1', '3.0', '2.7', '2.6', '2.5', '2.4', '2.3', '2.2' ]
+        ruby: [ ruby-head, '3.1', '3.0', '2.7', '2.6', '2.5', '2.4', '2.3', '2.2', truffleruby ]
     steps:
       - name: Checkout
         uses: actions/checkout@v2

Rakefile

@@ -7,11 +7,21 @@ Rake::TestTask.new(:test) do |t|
   t.test_files = FileList["test/**/test_*.rb"]
 end
 
-require "rake/extensiontask"
+if RUBY_ENGINE == "truffleruby"
+  task :compile do
+    # noop
+  end
 
-Rake::ExtensionTask.new("stackprof") do |ext|
-  ext.ext_dir = "ext/stackprof"
-  ext.lib_dir = "lib/stackprof"
+  task :clean do
+    # noop
+  end
+else
+  require "rake/extensiontask"
+
+  Rake::ExtensionTask.new("stackprof") do |ext|
+    ext.ext_dir = "ext/stackprof"
+    ext.lib_dir = "lib/stackprof"
+  end
 end
 
 task default: %i(compile test)

ext/stackprof/extconf.rb

@@ -1,4 +1,10 @@
 require 'mkmf'
+
+if RUBY_ENGINE == 'truffleruby'
+  File.write('Makefile', dummy_makefile($srcdir).join(""))
+  return
+end
+
 if have_func('rb_postponed_job_register_one') &&
    have_func('rb_profile_frames') &&
    have_func('rb_tracepoint_new') &&

lib/stackprof.rb

@@ -1,4 +1,8 @@
-require "stackprof/stackprof"
+if RUBY_ENGINE == 'truffleruby'
+  require "stackprof/truffleruby"
+else
+  require "stackprof/stackprof"
+end
 
 if defined?(RubyVM::YJIT) && RubyVM::YJIT.enabled?
   StackProf.use_postponed_job!

lib/stackprof/truffleruby.rb

@@ -0,0 +1,37 @@
+module StackProf
+  # Define the same methods as stackprof.c
+  class << self
+    def running?
+      false
+    end
+
+    def run(*args)
+      unimplemented
+    end
+
+    def start(*args)
+      unimplemented
+    end
+
+    def stop
+      unimplemented
+    end
+
+    def results(*args)
+      unimplemented
+    end
+
+    def sample
+      unimplemented
+    end
+
+    def use_postponed_job!
+      # noop
+    end
+
+    private def unimplemented
+      raise "Use --cpusampler=flamegraph or --cpusampler instead of StackProf on TruffleRuby.\n" \
+            "See https://www.graalvm.org/tools/profiling/ and `ruby --help:cpusampler` for more details."
+    end
+  end
+end

test/test_stackprof.rb

@@ -308,4 +308,4 @@ def idle
     r.close
     w.close
   end
-end
+end unless RUBY_ENGINE == 'truffleruby'

test/test_truffleruby.rb

@@ -0,0 +1,18 @@
+$:.unshift File.expand_path('../../lib', __FILE__)
+require 'stackprof'
+require 'minitest/autorun'
+
+if RUBY_ENGINE == 'truffleruby'
+  class StackProfTruffleRubyTest < MiniTest::Test
+    def test_error
+      error = assert_raises RuntimeError do
+        StackProf.run(mode: :cpu) do
+          unreacheable
+        end
+      end
+
+      assert_match(/TruffleRuby/, error.message)
+      assert_match(/--cpusampler/, error.message)
+    end
+  end
+end