process.c: Add Process._fork (#5017)

* process.c: Add Process._fork

This API is supposed for application monitoring libraries to hook fork
event.

[Feature #17795]

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>

1 files changed, 92 insertions, 0 deletions

diff --git a/test/ruby/test_process.rb b/test/ruby/test_process.rb
index 98c934945c..636871f822 100644
--- a/test/ruby/test_process.rb
+++ b/test/ruby/test_process.rb
@@ -2545,4 +2545,96 @@ EOS
     end
     assert_empty(Process.waitall)
   end
+
+  def test__fork
+    r, w = IO.pipe
+    pid = Process._fork
+    if pid == 0
+      begin
+        r.close
+        w << "ok: #$$"
+        w.close
+      ensure
+        exit!
+      end
+    else
+      w.close
+      assert_equal("ok: #{pid}", r.read)
+      r.close
+      Process.waitpid(pid)
+    end
+  end if Process.respond_to?(:_fork)
+
+  def test__fork_hook
+    %w(fork Process.fork).each do |method|
+      feature17795 = '[ruby-core:103400] [Feature #17795]'
+      assert_in_out_err([], <<-"end;", [], [], feature17795, timeout: 60) do |r, e|
+        module ForkHook
+          def _fork
+            p :before
+            ret = super
+            p :after
+            ret
+          end
+        end
+
+        Process.singleton_class.prepend(ForkHook)
+
+        pid = #{ method }
+        p pid
+        Process.waitpid(pid) if pid
+      end;
+        assert_equal([], e)
+        assert_equal(":before", r.shift)
+        assert_equal(":after", r.shift)
+        s = r.map {|s| s.chomp }.sort #=> [pid, ":after", "nil"]
+        assert_match(/^\d+$/, s[0]) # pid
+        assert_equal(":after", s[1])
+        assert_equal("nil", s[2])
+      end
+    end
+  end if Process.respond_to?(:_fork)
+
+  def test__fork_hook_popen
+    feature17795 = '[ruby-core:103400] [Feature #17795]'
+    assert_in_out_err([], <<-"end;", %w(:before :after :after foo bar), [], feature17795, timeout: 60)
+      module ForkHook
+        def _fork
+          p :before
+          ret = super
+          p :after
+          ret
+        end
+      end
+
+      Process.singleton_class.prepend(ForkHook)
+
+      IO.popen("-") {|io|
+        if !io
+          puts "foo"
+        else
+          puts io.read + "bar"
+        end
+      }
+    end;
+  end if Process.respond_to?(:_fork)
+
+  def test__fork_wrong_type_hook
+    feature17795 = '[ruby-core:103400] [Feature #17795]'
+    assert_in_out_err([], <<-"end;", ["OK"], [], feature17795, timeout: 60)
+      module ForkHook
+        def _fork
+          "BOO"
+        end
+      end
+
+      Process.singleton_class.prepend(ForkHook)
+
+      begin
+        fork
+      rescue TypeError
+        puts "OK"
+      end
+    end;
+  end if Process.respond_to?(:_fork)
 end