[GR-28450] Introduce SynchronizedArray to avoid race conditions on $LOADED_FEATURES and $LOAD_PATH.

PullRequest: truffleruby/2332

Author: Nicolas Laurent

spec/tags/truffle/synchronized_array_tags.txt

@@ -0,0 +1 @@
+slow:Truffle::SynchronizedArray redefines all Array and Enumerable methods

spec/truffle/synchronized_array_spec.rb

@@ -0,0 +1,31 @@
+# truffleruby_primitives: true
+
+# Copyright (c) 2020 Oracle and/or its affiliates. All rights reserved. This
+# code is released under a tri EPL/GPL/LGPL license. You can use it,
+# redistribute it and/or modify it under the terms of the:
+#
+# Eclipse Public License version 2.0, or
+# GNU General Public License version 2, or
+# GNU Lesser General Public License version 2.1.
+
+require_relative '../ruby/spec_helper'
+
+describe "Truffle::SynchronizedArray" do
+  it "redefines all Array and Enumerable methods" do
+    expected_methods = ruby_exe("puts Array.public_instance_methods(false) + Enumerable.public_instance_methods(false)")
+    expected_methods = expected_methods.lines(chomp: true).map { |line| line.to_sym }.uniq!.sort!
+    synchronized_methods = Truffle::SynchronizedArray.public_instance_methods(false).sort!
+
+    if synchronized_methods == expected_methods
+      synchronized_methods.should == synchronized_methods
+    else
+      # if the fast check fails, do a slower check to determine why
+      expected_methods.each do |m|
+        synchronized_methods.should include(m)
+      end
+      synchronized_methods.each do |m|
+        expected_methods.should include(m)
+      end
+    end
+  end
+end

src/main/java/org/truffleruby/core/CoreLibrary.java

@@ -978,6 +978,7 @@ public boolean isTruffleBootMainMethod(SharedMethodInfo info) {
             "/core/truffle/platform.rb",
             "/core/string.rb",
             "/core/random.rb",
+            "/core/truffle/synchronized_array.rb",
             "/core/truffle/kernel_operations.rb",
             "/core/truffle/exception_operations.rb",
             "/core/truffle/feature_loader.rb",

src/main/ruby/truffleruby/core/truffle/kernel_operations.rb

@@ -31,8 +31,8 @@ def self.define_read_only_global(name, getter)
       define_hooked_variable(name, getter, setter)
     end
 
-    LOAD_PATH = []
-    LOADED_FEATURES = []
+    LOAD_PATH = Truffle::SynchronizedArray.new
+    LOADED_FEATURES = Truffle::SynchronizedArray.new
 
     define_read_only_global(:$LOAD_PATH, -> { LOAD_PATH })
     define_read_only_global(:$LOADED_FEATURES, -> { LOADED_FEATURES })