Revert SIGCHLD changes to diagnose CI failures. (#7517)

* Revert "Remove special handling of `SIGCHLD`. (#7482)"

This reverts commit 44a0711eab7fbc71ac2c8ff489d8c53e97a8fe75.

* Revert "Remove prototypes for functions that are no longer used. (#7497)"

This reverts commit 4dce12bead3bfd91fd80b5e7195f7f540ffffacb.

* Revert "Remove SIGCHLD `waidpid`. (#7476)"

This reverts commit 1658e7d96696a656d9bd0a0c84c82cde86914ba2.

* Fix change to rjit variable name.

1 files changed, 43 insertions, 0 deletions

diff --git a/test/ruby/test_signal.rb b/test/ruby/test_signal.rb
index 7877a35129..c5043eea59 100644
--- a/test/ruby/test_signal.rb
+++ b/test/ruby/test_signal.rb
@@ -323,6 +323,49 @@ class TestSignal < Test::Unit::TestCase
     end;
   end
 
+  def test_sigchld_ignore
+    omit 'no SIGCHLD' unless Signal.list['CHLD']
+    old = trap(:CHLD, 'IGNORE')
+    cmd = [ EnvUtil.rubybin, '--disable=gems', '-e' ]
+    assert(system(*cmd, 'exit!(0)'), 'no ECHILD')
+    IO.pipe do |r, w|
+      pid = spawn(*cmd, "STDIN.read", in: r)
+      nb = Process.wait(pid, Process::WNOHANG)
+      th = Thread.new(Thread.current) do |parent|
+        Thread.pass until parent.stop? # wait for parent to Process.wait
+        w.close
+      end
+      assert_raise(Errno::ECHILD) { Process.wait(pid) }
+      th.join
+      assert_nil nb
+    end
+
+    IO.pipe do |r, w|
+      pids = 3.times.map { spawn(*cmd, 'exit!', out: w) }
+      w.close
+      zombies = pids.dup
+      assert_nil r.read(1), 'children dead'
+
+      Timeout.timeout(10) do
+        zombies.delete_if do |pid|
+          begin
+            Process.kill(0, pid)
+            false
+          rescue Errno::ESRCH
+            true
+          end
+        end while zombies[0]
+      end
+      assert_predicate zombies, :empty?, 'zombies leftover'
+
+      pids.each do |pid|
+        assert_raise(Errno::ECHILD) { Process.waitpid(pid) }
+      end
+    end
+  ensure
+    trap(:CHLD, old) if Signal.list['CHLD']
+  end
+
   def test_sigwait_fd_unused
     t = EnvUtil.apply_timeout_scale(0.1)
     assert_separately([], <<-End)