error.c: evaluate RARRAY_AREF once

* error.c (rb_check_backtrace): evaluate RARRAY_AREF only once.
  the first argument of RB_TYPE_P is expanded twice for non-immediate
  types.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41469 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 2 insertions, 1 deletions

diff --git a/error.c b/error.c
index e65e04fc10..eac254ca44 100644
--- a/error.c
+++ b/error.c
@@ -721,7 +721,8 @@ rb_check_backtrace(VALUE bt)
 	    rb_raise(rb_eTypeError, err);
 	}
 	for (i=0;i<RARRAY_LEN(bt);i++) {
-	    if (!RB_TYPE_P(RARRAY_AREF(bt, i), T_STRING)) {
+	    VALUE e = RARRAY_AREF(bt, i);
+	    if (!RB_TYPE_P(e, T_STRING)) {
 		rb_raise(rb_eTypeError, err);
 	    }
 	}