thread_pthread.c: get current main thread stack size

* thread_pthread.c: get current main thread stack size, which may
  be expanded than allocated size at initialization, by rlimit().
  [ruby-core:60113] [Bug #9454]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44712 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_exception.rb

@@ -488,6 +488,16 @@ end.join
   rescue SystemStackError
   end
 
+  def test_machine_stackoverflow_by_define_method
+    bug9454 = '[ruby-core:60113] [Bug #9454]'
+    assert_separately([], <<-SRC)
+    assert_raise(SystemStackError, #{bug9454.dump}) {
+      define_method(:foo) {self.foo}
+      self.foo
+    }
+    SRC
+  end
+
   def test_cause
     msg = "[Feature #8257]"
     cause = nil