test_recovery_sigint: Ensure precondition is met (#829)

* test_recovery_sigint: Ensure precondition is met

test_recovery_sigint depends on its process has SIG_DEF sigaction for
SIGINT. When its parent process set SIG_IGN which inherits to children,
then this test fails. This patch ensures this precondition met
regardless of inherited sigaction from its parent.

* Add test for restoration of other SIGINT handlers

Add another variant of test_recovery_sigint to ensure IRB to preserve
existing SIGINT handler other than SIG_DEF.

test/irb/test_init.rb

@@ -66,10 +66,18 @@ def test_rc_file_in_subdir
       end
     end
 
-    def test_recovery_sigint
+    def test_sigint_restore_default
       pend "This test gets stuck on Solaris for unknown reason; contribution is welcome" if RUBY_PLATFORM =~ /solaris/
       bundle_exec = ENV.key?('BUNDLE_GEMFILE') ? ['-rbundler/setup'] : []
-      status = assert_in_out_err(bundle_exec + %w[-W0 -rirb -e binding.irb;loop{Process.kill("SIGINT",$$)} -- -f --], "exit\n", //, //)
+      # IRB should restore SIGINT handler
+      status = assert_in_out_err(bundle_exec + %w[-W0 -rirb -e Signal.trap("SIGINT","DEFAULT");binding.irb;loop{Process.kill("SIGINT",$$)} -- -f --], "exit\n", //, //)
+      Process.kill("SIGKILL", status.pid) if !status.exited? && !status.stopped? && !status.signaled?
+    end
+
+    def test_sigint_restore_block
+      bundle_exec = ENV.key?('BUNDLE_GEMFILE') ? ['-rbundler/setup'] : []
+      # IRB should restore SIGINT handler
+      status = assert_in_out_err(bundle_exec + %w[-W0 -rirb -e x=false;Signal.trap("SIGINT"){x=true};binding.irb;loop{Process.kill("SIGINT",$$);if(x);break;end} -- -f --], "exit\n", //, //)
       Process.kill("SIGKILL", status.pid) if !status.exited? && !status.stopped? && !status.signaled?
     end