From 87b1a0d4a833dd0b2164481be45f7d1c59375040 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Fri, 15 Oct 2021 17:58:05 +0200
Subject: Add boilerplate for GC allocator

---
 src/bootstrap/gc.c   | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/bootstrap/main.c |  7 +++++--
 2 files changed, 53 insertions(+), 2 deletions(-)
 create mode 100644 src/bootstrap/gc.c

(limited to 'src/bootstrap')

diff --git a/src/bootstrap/gc.c b/src/bootstrap/gc.c
new file mode 100644
index 0000000..fff4201
--- /dev/null
+++ b/src/bootstrap/gc.c
@@ -0,0 +1,48 @@
+typedef struct GC {
+    Object *obj_list;
+    // Free list keeps track of the offset numbers from the obj_list
+    size_t *free_list;
+    size_t obj_size;
+    size_t obj_cap;
+    size_t fl_pos;
+    size_t available_slots;
+} GC;
+
+// FIXME: small value for testing purposes
+#define GC_INITIAL_HEAP 100000
+
+static GC gc;
+
+void
+init_gc(void) {
+    gc = (GC){
+        .obj_cap = GC_INITIAL_HEAP,
+        .available_slots = GC_INITIAL_HEAP,
+    };
+    gc.free_list = malloc(GC_INITIAL_HEAP * sizeof(size_t *));
+    gc.obj_list = malloc(GC_INITIAL_HEAP * sizeof(Object *));
+
+    // The free list stores the offset from the initial position for all
+    // available slots.
+    for (size_t i = 0; i < gc.obj_cap; i++) {
+        gc.free_list[i] = i;
+    }
+}
+
+Object *
+alloc_object(ObjectType type) {
+    if (gc.available_slots == 0) {
+        // TODO: trigger garbage collection.
+        if (gc.available_slots == 0) {
+            // TODO: grow heap tables.
+            // NOTE: When growing the tables, we might lose the pointer
+            // references! Should we work with offsets all the way?  That is for
+            // cdr and car? Should we have a utility function?
+        }
+    }
+    size_t slot = gc.free_list[gc.fl_pos++];
+    gc.available_slots--;
+    Object *obj = gc.obj_list + slot;
+    obj->type = type;
+    return obj;
+}
diff --git a/src/bootstrap/main.c b/src/bootstrap/main.c
index 5191fd0..575a924 100755
--- a/src/bootstrap/main.c
+++ b/src/bootstrap/main.c
@@ -1,6 +1,7 @@
 #include <assert.h>
 #include <getopt.h>
 #include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -12,6 +13,7 @@
 #include "objects.c"
 #include "parser.c"
 #include "environment.c"
+#include "gc.c"
 #include "primitives.c"
 
 //
@@ -26,6 +28,9 @@
 
 void
 init(void) {
+    // Initialize garbage collector.
+    init_gc();
+
     // Initialize singletons.
     obj_nil = alloc_object(OBJ_TYPE_NIL);
     obj_true = alloc_object(OBJ_TYPE_BOOL);
@@ -99,7 +104,6 @@ process_source(const StringView *source) {
     while (has_next_token(&visitor) && peek_token(&visitor).type != TOKEN_EOF) {
         Object *root = parse_tree(&visitor);
         if (root == obj_err || errors_n != 0) {
-            free_objects(root);
             break;
         }
 
@@ -109,7 +113,6 @@ process_source(const StringView *source) {
             display(result);
             printf("\n");
         }
-        free_objects(root);
     }
 
     if (tokens.buf != NULL) {
-- 
cgit v1.2.1