From afaa53bb7f669fc25d4fe4ff009e482dfb83666d Mon Sep 17 00:00:00 2001
From: Max Regan <mgregan2@gmail.com>
Date: Tue, 29 Nov 2022 21:21:16 -0500
Subject: [PATCH] Implement pin-based gc

This will allow for cleanup to occur mid-calculation when used throughout
---
 src/lisp.h   |  4 ++--
 src/memory.c | 35 +++++++++++++----------------------
 src/scope.c  |  4 +++-
 3 files changed, 18 insertions(+), 25 deletions(-)

diff --git a/src/lisp.h b/src/lisp.h
index e12aa86..29ebc93 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -38,8 +38,8 @@ void ucl_add_special(struct ucl *state, const char *name, ucl_lisp fun);
         if (len != 2) {                                                 \
             return NULL;                                                \
         }                                                               \
-        struct ucl_object *arg0 = ucl_list_nth(args, 0);           \
-        struct ucl_object *arg1 = ucl_list_nth(args, 1);           \
+        struct ucl_object *arg0 = ucl_list_nth(args, 0);                \
+        struct ucl_object *arg1 = ucl_list_nth(args, 1);                \
         return func_name##_impl(ucl, scope, arg0, arg1);                \
     }                                                                   \
     static struct ucl_object *func_name##_impl(UNUSED struct ucl *ucl_name, UNUSED struct ucl_scope *scope, struct ucl_object *arg0_name, struct ucl_object *arg1_name)
diff --git a/src/memory.c b/src/memory.c
index de21228..3722dab 100644
--- a/src/memory.c
+++ b/src/memory.c
@@ -83,7 +83,7 @@ void ucl_object_pin(struct ucl_object *obj) {
     obj->flags |= UCL_OBJ_FLAG_PINNED;
 }
 
-void ucl_object_unpinned(struct ucl_object *obj) {
+void ucl_object_unpin(struct ucl_object *obj) {
     obj->flags &= ~UCL_OBJ_FLAG_PINNED;
 }
 
@@ -131,52 +131,43 @@ void ucl_object_delete(struct ucl* state, struct ucl_object *obj) {
     ucl_object_delete_internal(state->obj_arena, obj);
 }
 
-static void ucl_object_mark(struct ucl_object *obj) {
+static void ucl_object_mark_recursive(struct ucl_object *obj) {
     if (obj == NULL || obj->flags & UCL_OBJ_FLAG_REACHABLE) {
         return;
     }
 
-    obj->flags |= 1;
+    obj->flags |= UCL_OBJ_FLAG_REACHABLE;
     if (obj->type == UCL_TYPE_CELL) {
-        ucl_object_mark(obj->cell.car);
-        ucl_object_mark(obj->cell.cdr);
+        ucl_object_mark_recursive(obj->cell.car);
+        ucl_object_mark_recursive(obj->cell.cdr);
     }
 }
 
-static void ucl_scope_mark(struct ucl_arena * arena, void *obj) {
+static void ucl_gc_mark_pinned(struct ucl_arena * arena, void *obj) {
     (void) arena;
-    struct ucl_scope *scope = (struct ucl_scope *) obj;
+    struct ucl_object *object = (struct ucl_object *) obj;
 
-    ucl_object_mark(scope->list);
+    if (object->flags & UCL_OBJ_FLAG_PINNED) {
+        ucl_object_mark_recursive(object);
+    }
 }
 
-static void ucl_gc_unmark(struct ucl_arena * arena, void *obj) {
+static void ucl_gc_unmark_all(struct ucl_arena * arena, void *obj) {
     (void) arena;
     struct ucl_object *object = (struct ucl_object *) obj;
     object->flags &= ~UCL_OBJ_FLAG_REACHABLE;
 }
 
 static void ucl_gc_sweep(struct ucl_arena * arena, void *obj) {
-    (void) arena;
     struct ucl_object *object = (struct ucl_object *) obj;
     if (!(object->flags &UCL_OBJ_FLAG_REACHABLE)) {
          ucl_object_delete_internal(arena, object);
     }
 }
 
-// TODO: Implement full cleanup
-/* static void ucl_gc_deleteall(struct ucl_arena * arena, void *obj) { */
-/*     (void) arena; */
-/*     struct ucl_object *object = (struct ucl_object *) obj; */
-/*     ucl_object_delete_internal(arena, object); */
-/* } */
-
-
 void ucl_gc(struct ucl* ucl) {
-    // TODO: Implement scope cleanup
-
-    ucl_arena_map(ucl->obj_arena, ucl_gc_unmark);
-    ucl_arena_map(ucl->scope_arena, ucl_scope_mark);
+    ucl_arena_map(ucl->obj_arena, ucl_gc_unmark_all);
+    ucl_arena_map(ucl->obj_arena, ucl_gc_mark_pinned);
     ucl_arena_map(ucl->obj_arena, ucl_gc_sweep);
 }
 
diff --git a/src/scope.c b/src/scope.c
index 931d547..6c0a0eb 100644
--- a/src/scope.c
+++ b/src/scope.c
@@ -60,12 +60,14 @@ struct ucl_scope *ucl_scope_create(struct ucl *state) {
     struct ucl_scope *scope = ucl_arena_get(state->scope_arena);
     scope->list = ucl_nil_create(state);
     scope->parent = NULL;
+    ucl_object_pin(scope->list);
     return scope;
 }
 
 struct ucl_scope *ucl_scope_create_child(struct ucl *state, struct ucl_scope *parent) {
     struct ucl_scope *scope = ucl_scope_create(state);
     scope->parent = parent;
+    ucl_object_pin(scope->list);
     return scope;
 }
 
@@ -78,6 +80,6 @@ struct ucl_scope *ucl_scope_get_root(struct ucl_scope *scope) {
 
 void ucl_scope_delete(struct ucl *ucl, struct ucl_scope *scope) {
     assert(ucl->scope_arena != NULL);
+    ucl_object_unpin(scope->list);
     ucl_arena_put(ucl->scope_arena, scope);
-    // Garbage collection will handle the objects, they are shared
 }