1 files changed, 20 insertions, 6 deletions

diff --git a/eval_error.c b/eval_error.c
index f9756f65ac..8ea58a4742 100644
--- a/eval_error.c
+++ b/eval_error.c
@@ -222,23 +222,36 @@ print_backtrace(const VALUE eclass, const VALUE errat, const VALUE str, int reve
 
 VALUE rb_get_message(VALUE exc);
 
+static int
+shown_cause_p(VALUE cause, VALUE *shown_causes)
+{
+    VALUE shown = *shown_causes;
+    if (!shown) {
+        *shown_causes = shown = rb_obj_hide(rb_ident_hash_new());
+    }
+    if (rb_hash_has_key(shown, cause)) return TRUE;
+    rb_hash_aset(shown, cause, Qtrue);
+    return FALSE;
+}
+
 static void
-show_cause(VALUE errinfo, VALUE str, VALUE highlight, VALUE reverse)
+show_cause(VALUE errinfo, VALUE str, VALUE highlight, VALUE reverse, VALUE *shown_causes)
 {
     VALUE cause = rb_attr_get(errinfo, id_cause);
-    if (!NIL_P(cause) && rb_obj_is_kind_of(cause, rb_eException)) {
+    if (!NIL_P(cause) && rb_obj_is_kind_of(cause, rb_eException) &&
+        !shown_cause_p(cause, shown_causes)) {
         volatile VALUE eclass = CLASS_OF(cause);
         VALUE errat = rb_get_backtrace(cause);
         VALUE emesg = rb_get_message(cause);
         if (reverse) {
-            show_cause(cause, str, highlight, reverse);
+            show_cause(cause, str, highlight, reverse, shown_causes);
             print_backtrace(eclass, errat, str, TRUE);
             print_errinfo(eclass, errat, emesg, str, highlight!=0);
         }
         else {
             print_errinfo(eclass, errat, emesg, str, highlight!=0);
             print_backtrace(eclass, errat, str, FALSE);
-            show_cause(cause, str, highlight, reverse);
+            show_cause(cause, str, highlight, reverse, shown_causes);
         }
     }
 }
@@ -247,6 +260,7 @@ void
 rb_error_write(VALUE errinfo, VALUE emesg, VALUE errat, VALUE str, VALUE highlight, VALUE reverse)
 {
     volatile VALUE eclass;
+    VALUE shown_causes = 0;
 
     if (NIL_P(errinfo))
 	return;
@@ -277,14 +291,14 @@ rb_error_write(VALUE errinfo, VALUE emesg, VALUE errat, VALUE str, VALUE highlig
 	    len = p - (msg = buff);
 	}
 	write_warn2(str, msg, len);
-        show_cause(errinfo, str, highlight, reverse);
+        show_cause(errinfo, str, highlight, reverse, &shown_causes);
 	print_backtrace(eclass, errat, str, TRUE);
 	print_errinfo(eclass, errat, emesg, str, highlight!=0);
     }
     else {
 	print_errinfo(eclass, errat, emesg, str, highlight!=0);
 	print_backtrace(eclass, errat, str, FALSE);
-        show_cause(errinfo, str, highlight, reverse);
+        show_cause(errinfo, str, highlight, reverse, &shown_causes);
     }
 }