Add GC stub, let1
diff --git a/src/lisp/gc.c b/src/lisp/gc.c
new file mode 100644
index 0000000..21e38e2
--- /dev/null
+++ b/src/lisp/gc.c
@@ -0,0 +1,23 @@
+#include "gc.h"
+#include "lisp.h"
+
+void _mark(unsigned int value)
+{
+
+}
+
+void _sweep()
+{
+
+}
+
+void _do_gc(unsigned int esp, unsigned int ebp)
+{
+	unsigned int *esp_p = (unsigned int *)esp,
+		*ebp_p = (unsigned int *)ebp;
+	
+	for (int i = 0; esp_p + i < ebp_p; i++)
+	{
+		_mark(esp_p[i]);
+	}
+}