From b5641c3ff27f27df819d1ef6693beb86a478179e Mon Sep 17 00:00:00 2001
From: Matt Valentine-House <matt@eightbitraptor.com>
Date: Thu, 24 Oct 2024 16:10:50 +0100
Subject: [PATCH] Initialise the VM context in each MMTk worker in Debug

This is to ensure an assertion in vm.c is never false
---
 gc.c      |  4 ++--
 gc/mmtk.c | 14 ++++++++++----
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/gc.c b/gc.c
index 4d773f7d2cae5a..3553e505abc8d5 100644
--- a/gc.c
+++ b/gc.c
@@ -183,9 +183,9 @@ rb_gc_initialize_vm_context(struct rb_gc_vm_context *context)
 void
 rb_gc_worker_thread_set_vm_context(struct rb_gc_vm_context *context)
 {
+#if !RUBY_DEBUG
     rb_native_mutex_lock(&context->lock);
-
-    GC_ASSERT(rb_current_execution_context(false) == NULL);
+#endif
 
 #ifdef RB_THREAD_LOCAL_SPECIFIER
 # ifdef __APPLE__
diff --git a/gc/mmtk.c b/gc/mmtk.c
index 2389071aa0fdf6..ba229fe4b4ea01 100644
--- a/gc/mmtk.c
+++ b/gc/mmtk.c
@@ -81,6 +81,10 @@ static void
 rb_mmtk_init_gc_worker_thread(MMTk_VMWorkerThread gc_thread_tls)
 {
     rb_mmtk_gc_thread_tls = gc_thread_tls;
+#if RUBY_DEBUG
+    struct objspace *objspace = rb_gc_get_objspace();
+    rb_gc_worker_thread_set_vm_context(&objspace->vm_context);
+#endif
 }
 
 static bool
@@ -246,7 +250,6 @@ rb_mmtk_scan_roots_in_mutator_thread(MMTk_VMMutatorThread mutator, MMTk_VMWorker
 {
     if (mutator->gc_mutator_p) {
         struct objspace *objspace = rb_gc_get_objspace();
-
         rb_gc_worker_thread_set_vm_context(&objspace->vm_context);
         rb_gc_mark_roots(objspace, NULL);
         rb_gc_worker_thread_unset_vm_context(&objspace->vm_context);
@@ -256,7 +259,9 @@ rb_mmtk_scan_roots_in_mutator_thread(MMTk_VMMutatorThread mutator, MMTk_VMWorker
 static void
 rb_mmtk_scan_object_ruby_style(MMTk_ObjectReference object)
 {
-    rb_gc_mark_children(rb_gc_get_objspace(), (VALUE)object);
+    struct objspace *objspace = rb_gc_get_objspace();
+    rb_gc_worker_thread_set_vm_context(&objspace->vm_context);
+    rb_gc_mark_children(objspace, (VALUE)object);
 }
 
 static void
@@ -270,6 +275,7 @@ rb_mmtk_call_obj_free(MMTk_ObjectReference object)
 {
     VALUE obj = (VALUE)object;
     struct objspace *objspace = rb_gc_get_objspace();
+    rb_gc_worker_thread_set_vm_context(&objspace->vm_context);
 
     if (RB_UNLIKELY(rb_gc_event_hook_required_p(RUBY_INTERNAL_EVENT_FREEOBJ))) {
         rb_gc_worker_thread_set_vm_context(&objspace->vm_context);
@@ -788,13 +794,13 @@ rb_gc_impl_remove_weak(void *objspace_ptr, VALUE parent_obj, VALUE *ptr)
 bool
 rb_gc_impl_object_moved_p(void *objspace_ptr, VALUE obj)
 {
-    rb_bug("unimplemented");
+    return false;
 }
 
 VALUE
 rb_gc_impl_location(void *objspace_ptr, VALUE value)
 {
-    rb_bug("unimplemented");
+    return value;
 }
 
 // Write barriers