diff --git a/include/rc.h b/include/rc.h
index d113d4b..a794441 100644
--- a/include/rc.h
+++ b/include/rc.h
@@ -45,8 +45,10 @@ rc_ptr_t rc_clone(rc_const_ptr_t ptr) _rc_mut_fn _rc_attr((returns_nonnull));
 size_t rc_refs(rc_const_ptr_t ptr)_rc_fn;
 rc_bool rc_is_valid(rc_const_ptr_t ptr) _rc_fn;
 
-rc_weak_t* _rc_restrict rc_create_weak(rc_const_ptr_t ptr) _rc_gmut_fn _rc_alloc_fn;
+rc_weak_t* _rc_restrict rc_downgrade(rc_const_ptr_t ptr) _rc_gmut_fn _rc_alloc_fn;
+rc_ptr_t rc_weak_upgrade(const rc_weak_t * _rc_restrict weak);
 void rc_weak_free(rc_weak_t* _rc_restrict ptr) _rc_gmut_fn;
+rc_ptr_t rc_weak_upgrade(const rc_weak_t * _rc_restrict weak) _rc_mut_fn;
 
 #ifdef __cplusplus
 }
diff --git a/src/rc.c b/src/rc.c
index 99baff0..6454769 100644
--- a/src/rc.c
+++ b/src/rc.c
@@ -5,6 +5,8 @@
 
 #include <rc.h>
 
+#include "vector.h"
+
 #define RC_CHK 0xabadcafe
 
 
@@ -12,17 +14,18 @@ struct rc {
 	uint32_t check;
 	_Atomic size_t refs;
 	_Atomic size_t weak_refs;
-	//TODO: Keep all weak pointers here. rc_weak_free() should remove its own pointer address from that.
+
+	vec_t* _rc_restrict weaks; //vec type `rc_weak_t*`
 
 	uint8_t ptr[];
 };
 
 struct rc_weak {
-	_Atomic int is_valid;
+	_Atomic rc_bool is_valid;
 	const struct rc* _rc_attr((may_alias)) _ptr;
 }; 
 
-_rc_attr((noreturn)) static void panic(const char* string, ...)
+_rc_attr((noreturn)) void panic(const char* string, ...)
 {
 	va_list args;
 	va_start(args, string);
@@ -75,6 +78,7 @@ _rc_attr((nonnull)) inline static void rc_checkptr(const struct rc* rc)
 	rc->check = RC_CHK;
 	rc->refs = 1;
 	rc->weak_refs =0;
+	rc->weaks = vec_new();
 
 	return (void*) rc->ptr;	
 }
@@ -83,7 +87,13 @@ _rc_attr((nonnull)) inline static void rc_checkptr(const struct rc* rc)
 {
 	register rc_t rc = ptr_rev(ptr);
 	rc_checkptr(rc);
-	if (!--rc->refs) free(rc);
+	if (!--rc->refs) {
+		for(size_t i=0;i<rc->weaks->len;i++) {
+			vec_tnptr(rc_weak_t, rc->weaks->buffer[i])->is_valid = RC_FALSE;
+		}
+		free(rc->weaks);
+		free(rc);
+	}
 }
 
 _rc_mut_fn _rc_attr((returns_nonnull)) rc_ptr_t rc_clone(rc_const_ptr_t ptr)
@@ -108,13 +118,16 @@ _rc_fn rc_bool rc_is_valid(rc_const_ptr_t ptr)
 		&& rc->refs>0;
 }
 
-_rc_alloc_fn _rc_gmut_fn rc_weak_t* _rc_restrict rc_create_weak(rc_const_ptr_t ptr)
+_rc_alloc_fn _rc_gmut_fn rc_weak_t* _rc_restrict rc_downgrade(rc_const_ptr_t ptr)
 {
 	register rc_t rc = ptr_ucrev(ptr);
 	rc_weak_t* weak = calloc(sizeof(rc_weak_t), 1);
 	
+	//TODO: push `weak` to rc->weaks
+
 	weak->_ptr = rc;
-	weak->is_valid = 1;
+	weak->is_valid = RC_TRUE;
+
 
 	rc->weak_refs++;
 	return weak;
@@ -125,7 +138,22 @@ _rc_gmut_fn void rc_weak_free(rc_weak_t* _rc_restrict ptr)
 	if (ptr->is_valid) {
 		struct rc* _rc_attr((may_alias)) rc = (struct rc* _rc_attr((may_alias)))ptr->_ptr;
 		rc_checkptr(rc);
+
+		//TODO: remove `weak` from `rc->weaks`
 		rc->weak_refs--;
 	}
 	free(ptr);
 }
+
+_rc_mut_fn rc_ptr_t rc_weak_upgrade(const rc_weak_t * _rc_restrict weak)
+{
+	if (weak->is_valid) {
+		struct rc* _rc_attr((may_alias)) rc = (struct rc* _rc_attr((may_alias)))weak->_ptr;
+		
+		if (rc->check == RC_CHK && rc->refs>0) {
+			rc->refs++;
+			return rc->ptr;
+		}
+	}
+	return NULL;
+}
diff --git a/src/vector.c b/src/vector.c
new file mode 100644
index 0000000..f4c33e7
--- /dev/null
+++ b/src/vector.c
@@ -0,0 +1,22 @@
+#include <stdlib.h>
+#include <string.h>
+
+#include "vector.h"
+
+extern void panic(const char* string, ...) _rc_attr((noreturn));
+
+_rc_attr((noinline, noreturn, cold)) static void _fail_vec_alloc(size_t cap)
+{
+	panic("vec_alloc(): malloc() failed to allocate %d bytes (cap %d)", sizeof(vec_t) + (cap * sizeof(vec_elem_t)), cap);
+}
+
+_rc_alloc_fn vec_t* _rc_restrict vec_alloc(size_t cap)
+{
+	vec_t* vec = malloc(sizeof(vec_t) + (cap * sizeof(vec_elem_t)));
+	if(!vec) _fail_vec_alloc(cap);
+	vec-> cap = cap;
+	vec-> scap = cap;
+	vec-> len = 0;
+
+	return vec;
+}
diff --git a/src/vector.h b/src/vector.h
new file mode 100644
index 0000000..6c5baae
--- /dev/null
+++ b/src/vector.h
@@ -0,0 +1,27 @@
+#ifndef _VECTOR_H
+#define _VECTOR_H
+
+#include <rc.h>
+
+#define VEC_DEFAULT_CAP 16
+
+
+typedef void* vec_elem_t;
+typedef struct vec vec_t;
+
+struct vec {
+	size_t scap;
+
+	size_t cap;
+	size_t len;
+
+	vec_elem_t buffer[];
+};
+
+#define vec_new() vec_alloc(VEC_DEFAULT_CAP)
+#define vec_free(vec) free(vec)
+#define vec_tnptr(ty, elem) ((ty *)(elem))
+
+vec_t* _rc_restrict vec_alloc(size_t cap) _rc_alloc_fn;
+
+#endif /* _VECTOR_H */