diff --git a/include/picrin.h b/include/picrin.h
index 97108842..047dea57 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -6,6 +6,10 @@
 typedef struct {
 } pic_state;
 
+void *pic_alloc(pic_state *, size_t);
+struct pic_object *pic_gc_alloc(pic_state *, size_t, enum pic_tt);
+void pic_free(pic_state *, void *);
+
 pic_state *pic_open();
 void pic_close(pic_state *);
 
diff --git a/src/gc.c b/src/gc.c
new file mode 100644
index 00000000..a1dac877
--- /dev/null
+++ b/src/gc.c
@@ -0,0 +1,27 @@
+#include <stdlib.h>
+
+#include "picrin.h"
+
+void *
+pic_alloc(pic_state *pic, size_t size)
+{
+  /* mock */
+  return malloc(size);
+}
+
+struct pic_object *
+pic_gc_alloc(pic_state *pic, size_t size, enum pic_tt tt)
+{
+  struct pic_object *obj;
+
+  obj = (struct pic_object *)malloc(size);
+  obj->tt = tt;
+
+  return obj;
+}
+
+void
+pic_free(pic_state *pic, void *ptr)
+{
+  free(ptr);
+}