merge revision(s) 57137: [Backport #13043]

	eval.c: fix circular cause

	* eval.c (exc_setup_cause): always set cause of cause to get rid
  of circular references.  [ruby-core:78688] [Bug #13043]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@57222 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 3 insertions, 0 deletions

diff --git a/eval.c b/eval.c
index fbd28565ed..a8935ff7ce 100644
--- a/eval.c
+++ b/eval.c
@@ -468,6 +468,9 @@ exc_setup_cause(VALUE exc, VALUE cause)
 #endif
     if (!NIL_P(cause) && cause != exc) {
 	rb_ivar_set(exc, id_cause, cause);
+	if (!rb_ivar_defined(cause, id_cause)) {
+	    rb_ivar_set(cause, id_cause, Qnil);
+	}
     }
     return exc;
 }