Make Digest() thread-safe.

* ext/digest/lib/digest.rb (Digest()): This function should now be
  thread-safe.  If you have a problem with regard to on-demand
  loading under a multi-threaded environment, preload "digest/*"
  modules on boot or use this method instead of directly
  referencing Digest::*. [Bug #9494]
  cf. https://github.com/aws/aws-sdk-ruby/issues/525

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48213 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 71 insertions, 0 deletions

diff --git a/test/digest/digest/foo.rb b/test/digest/digest/foo.rb
new file mode 100644
index 0000000000..d576ef00e0
--- /dev/null
+++ b/test/digest/digest/foo.rb
@@ -0,0 +1,10 @@
+module Digest
+  Foo = nil
+
+  sleep 0.2
+
+  remove_const(:Foo)
+
+  class Foo < Class
+  end
+end
diff --git a/test/digest/test_digest.rb b/test/digest/test_digest.rb
index f4ec0234f1..ccf0a26b90 100644
--- a/test/digest/test_digest.rb
+++ b/test/digest/test_digest.rb
@@ -208,4 +208,65 @@ module TestDigest
       end
     end
   end
+
+  class TestDigestParen < Test::Unit::TestCase
+    def test_sha2
+      assert_separately(%w[-rdigest], <<-'end;')
+        assert_nothing_raised {
+          Digest(:SHA256).new
+          Digest(:SHA384).new
+          Digest(:SHA512).new
+        }
+      end;
+    end
+
+    def test_no_lib
+      assert_separately(%w[-rdigest], <<-'end;')
+        class Digest::Nolib < Digest::Class
+        end
+
+        assert_nothing_raised {
+          Digest(:Nolib).new
+        }
+      end;
+    end
+
+    def test_no_lib_no_def
+      assert_separately(%w[-rdigest], <<-'end;')
+        assert_raise(LoadError) {
+          Digest(:Nodef).new
+        }
+      end;
+    end
+
+    def test_race
+      assert_separately(['-rdigest', "-I#{File.dirname(__FILE__)}"], <<-'end;')
+        assert_nothing_raised {
+          t = Thread.start {
+            sleep 0.1
+            Digest(:Foo).new
+          }
+          Digest(:Foo).new
+          t.join
+        }
+      end;
+    end
+
+    def test_race_mixed
+      assert_separately(['-rdigest', "-I#{File.dirname(__FILE__)}"], <<-'end;')
+        assert_nothing_raised {
+          t = Thread.start {
+            sleep 0.1
+            Digest::Foo.new
+          }
+          Digest(:Foo).new
+          begin
+            t.join
+          rescue NoMethodError, NameError
+            # NoMethodError is highly likely; NameError is listed just in case
+          end
+        }
+      end;
+    end
+  end
 end