From 4fe8b074bb245e049b6fecbd259af01903586a0e Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Wed, 13 Sep 2023 23:50:39 +0900
Subject: [PATCH] gc.c: remove `prev` link from mrb_heap_page

---
 src/gc.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/src/gc.c b/src/gc.c
index 537414792..ddfa9fbf4 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -150,7 +150,6 @@ typedef struct {
 
 typedef struct mrb_heap_page {
   struct RBasic *freelist;
-  struct mrb_heap_page *prev;
   struct mrb_heap_page *next;
   struct mrb_heap_page *free_next;
   mrb_bool old:1;
@@ -312,8 +311,6 @@ add_heap(mrb_state *mrb, mrb_gc *gc)
   page->freelist = prev;
 
   page->next = gc->heaps;
-  if (gc->heaps)
-    gc->heaps->prev = page;
   gc->heaps = page;
 
   page->free_next = gc->free_heaps;
@@ -1105,12 +1102,7 @@ incremental_sweep_phase(mrb_state *mrb, mrb_gc *gc, size_t limit)
     if (dead_slot) {
       mrb_heap_page *next = page->next;
 
-      mrb_assert(prev == page->prev);
-      /* unlink_heap_page */
-      if (page->prev)
-        page->prev->next = page->next;
-      if (page->next)
-        page->next->prev = page->prev;
+      if (prev) prev->next = next;
       if (gc->heaps == page)
         gc->heaps = page->next;