From 46bd055c0aaa82ebb1b2b68d491da791bd34c24c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=88=98=E7=9A=93?= <whiteaxe@tuta.io>
Date: Mon, 21 Apr 2025 11:16:21 -0400
Subject: [PATCH] Fix memory leak in `cont_restore_thread` in Ruby in libretro
 builds

---
 libretro/ruby-jump-buffer.patch | 54 +++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/libretro/ruby-jump-buffer.patch b/libretro/ruby-jump-buffer.patch
index c80f2222..26bd3bb4 100644
--- a/libretro/ruby-jump-buffer.patch
+++ b/libretro/ruby-jump-buffer.patch
@@ -1,5 +1,59 @@
 # Fixes a memory leak in WASI builds of Ruby where VM jump buffers are sometimes not freed.
 
+--- a/cont.c
++++ b/cont.c
+@@ -1518,6 +1518,51 @@ cont_restore_thread(rb_context_t *cont)
+             rb_raise(rb_eRuntimeError, "can't call across trace_func");
+         }
+ 
++#if defined(__wasm__) && !defined(__EMSCRIPTEN__)
++        if (th->ec->tag != sec->tag) {
++            /* find the lowest common ancestor tag of the current EC and the saved EC */
++
++            struct rb_vm_tag *lowest_common_ancestor = NULL;
++            size_t num_tags = 0;
++            size_t num_saved_tags = 0;
++            for (struct rb_vm_tag *tag = th->ec->tag; tag != NULL; tag = tag->prev) {
++                ++num_tags;
++            }
++            for (struct rb_vm_tag *tag = sec->tag; tag != NULL; tag = tag->prev) {
++                ++num_saved_tags;
++            }
++
++            size_t min_tags = num_tags <= num_saved_tags ? num_tags : num_saved_tags;
++
++            struct rb_vm_tag *tag = th->ec->tag;
++            while (num_tags > min_tags) {
++                tag = tag->prev;
++                --num_tags;
++            }
++
++            struct rb_vm_tag *saved_tag = sec->tag;
++            while (num_saved_tags > min_tags) {
++                saved_tag = saved_tag->prev;
++                --num_saved_tags;
++            }
++
++            while (min_tags > 0) {
++                if (tag == saved_tag) {
++                    lowest_common_ancestor = tag;
++                    break;
++                }
++                tag = tag->prev;
++                saved_tag = saved_tag->prev;
++                --min_tags;
++            }
++
++            /* free all the jump buffers between the current EC's tag and the lowest common ancestor tag */
++            for (struct rb_vm_tag *tag = th->ec->tag; tag != lowest_common_ancestor; tag = tag->prev) {
++                rb_vm_tag_jmpbuf_deinit(&tag->buf);
++            }
++        }
++#endif
++
+         /* copy vm stack */
+ #ifdef CAPTURE_JUST_VALID_VM_STACK
+         MEMCPY(th->ec->vm_stack,
 --- a/signal.c
 +++ b/signal.c
 @@ -849,6 +849,7 @@ check_stack_overflow(int sig, const uintptr_t addr, const ucontext_t *ctx)