https://git.ruby-lang.org/ruby.git/commit/?id=515b1989b1

From 515b1989b1093a4dddef83d0cda763c9ae6760e3 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <tenderlove@r...>
Date: Wed, 11 Sep 2019 14:02:05 -0700
Subject: Make NODE_ARYPTN layout consistent between Ripper and AST

We are seeing SEGVs in CI:

  http://ci.rvm.jp/results/trunk-gc-asserts@ruby-sky1/2253563

This is happening because Ripper constructs AST nodes differently than
parse.y normally does.  Specifically in this case Ripper is assigning 3
`VALUE` objects:

  https://github.com/ruby/ruby/blob/1febb6f4a14f7222c6d30250bfdc252d34238187/parse.y#L757-L761

Where parse.y will normally assign other things:

  https://github.com/ruby/ruby/blob/1febb6f4a14f7222c6d30250bfdc252d34238187/parse.y#L11258-L11260

The important one is the last one, the `struct rb_ary_pattern_info`. The
mark function assumed that `NODE_ARYPTN` have a pointer to `struct
rb_ary_pattern_info`, and used it:

  https://github.com/ruby/ruby/blob/1febb6f4a14f7222c6d30250bfdc252d34238187/node.c#L1269-L1274

In the case of Ripper, `NODE_ARYPTN` doesn't point to an
`rb_ary_pattern_info`, so the mark function would SEGV.  This commit
changes Ripper so that its `NODE_ARYPTN` nodes also point at an
`rb_ary_pattern_info`, and the mark function can continue with the same
assumption.

diff --git a/parse.y b/parse.y
index bb4191d..60fcf8c 100644
--- a/parse.y
+++ b/parse.y
@@ -732,7 +732,15 @@ static VALUE https://github.com/ruby/ruby/blob/trunk/parse.y#L732
 new_array_pattern(struct parser_params *p, VALUE constant, VALUE pre_arg, VALUE aryptn, const YYLTYPE *loc)
 {
     NODE *t = (NODE *)aryptn;
-    VALUE pre_args = t->u1.value, rest_arg = t->u2.value, post_args = t->u3.value;
+    struct rb_ary_pattern_info *apinfo = t->nd_apinfo;
+    VALUE pre_args = Qnil, rest_arg = Qnil, post_args = Qnil;
+
+    if (apinfo) {
+        pre_args = rb_ary_entry(apinfo->imemo, 0);
+        rest_arg = rb_ary_entry(apinfo->imemo, 1);
+        post_args = rb_ary_entry(apinfo->imemo, 2);
+    }
+
     if (!NIL_P(pre_arg)) {
 	if (!NIL_P(pre_args)) {
 	    rb_ary_unshift(pre_args, pre_arg);
@@ -748,17 +756,23 @@ static VALUE https://github.com/ruby/ruby/blob/trunk/parse.y#L756
 new_array_pattern_tail(struct parser_params *p, VALUE pre_args, VALUE has_rest, VALUE rest_arg, VALUE post_args, const YYLTYPE *loc)
 {
     NODE *t;
+    struct rb_ary_pattern_info *apinfo;
+
     if (has_rest) {
 	rest_arg = dispatch1(var_field, rest_arg ? rest_arg : Qnil);
     }
     else {
 	rest_arg = Qnil;
     }
-    t = rb_node_newnode(NODE_ARYPTN, pre_args, rest_arg, post_args, &NULL_LOC);
 
-    add_mark_object(p, pre_args);
-    add_mark_object(p, rest_arg);
-    add_mark_object(p, post_args);
+    apinfo = ZALLOC(struct rb_ary_pattern_info);
+    /* VALUE tmpbuf = rb_imemo_tmpbuf_auto_free_pointer(apinfo); */
+    VALUE tmpbuf = rb_imemo_new(imemo_tmpbuf, (VALUE)apinfo, 0, 0, 0);
+    apinfo->imemo = rb_ary_new_from_args(4, pre_args, rest_arg, post_args, tmpbuf);
+
+    t = rb_node_newnode(NODE_ARYPTN, Qnil, Qnil, (VALUE)apinfo, &NULL_LOC);
+    RB_OBJ_WRITTEN(p->ast, Qnil, apinfo->imemo);
+
     return (VALUE)t;
 }
 
-- 
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