transcode.c: add GC guard on raise

* transcode.c (econv_s_search_convpath): add GC guard to fix SEGV
  on raise.
  [Bug #15162] [ruby-core:89172]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64879 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

transcode.c

@@ -3155,8 +3155,12 @@ econv_s_search_convpath(int argc, VALUE *argv, VALUE klass)
     convpath = Qnil;
     transcode_search_path(sname, dname, search_convpath_i, &convpath);
 
-    if (NIL_P(convpath))
-        rb_exc_raise(rb_econv_open_exc(sname, dname, ecflags));
+    if (NIL_P(convpath)) {
+	VALUE exc = rb_econv_open_exc(sname, dname, ecflags);
+	RB_GC_GUARD(snamev);
+	RB_GC_GUARD(dnamev);
+	rb_exc_raise(exc);
+    }
 
     if (decorate_convpath(convpath, ecflags) == -1) {
 	VALUE exc = rb_econv_open_exc(sname, dname, ecflags);