diff --git a/byterun/.gitignore b/byterun/.gitignore
index 68995d9a0..514b6ec32 100644
--- a/byterun/.gitignore
+++ b/byterun/.gitignore
@@ -1 +1,10 @@
-/byterun.exe
\ No newline at end of file
+/byterun.exe
+
+build/
+.xmake/
+.cache/
+
+compile_commands.json
+
+*.a
+*.o
diff --git a/byterun/Makefile b/byterun/Makefile
index 64cf0ae60..c339568b7 100644
--- a/byterun/Makefile
+++ b/byterun/Makefile
@@ -3,7 +3,7 @@ FLAGS=-m32 -g2 -fstack-protector-all
 all: parser.o
 	$(CC) $(FLAGS) -o byterun parser.o ../runtime/runtime.a
 
-parser.o: src/parser.c
+interpreter.o: src/parser.c 
 	$(CC) $(FLAGS) -Iinclude/ -g -c src/parser.c
 
 clean:
diff --git a/byterun/include/builtin.h b/byterun/include/builtin.h
index 7a7f9bba0..b3a3d20f8 100644
--- a/byterun/include/builtin.h
+++ b/byterun/include/builtin.h
@@ -22,8 +22,6 @@ inline void f_length(struct State *s) {
 
   if (type == ARRAY_T || type == STR_T) {
     s_put_i(s, dh_param(x->array.data_header));
-  } else if (type == CONST_STR_T) {
-    s_put_i(s, strlen(x->const_str.value));
   } else if (type == STR_T) {
     s_put_i(s, strlen(x->str.value));
   } else { // TODO: lists ??
@@ -38,8 +36,10 @@ inline size_t str_sz(union VarT *var) {
     return strlen("<nil>");
   case INT_T: // int
     return snprintf(nullptr, 0, "%d", var->int_t.value);
-  case CONST_STR_T: // "str"
-    return strlen(var->const_str.value);
+  case BOX_T: // "<box>:..."
+    return strlen("<box>") + (var->box.value != NULL
+                                  ? str_sz((union VarT *)&var->box.value) + 1
+                                  : 0);
   case STR_T: // "str"
     return strlen(var->str.value);
   case CLOJURE_T: // <clojure> // TODO
@@ -49,7 +49,7 @@ inline size_t str_sz(union VarT *var) {
     size_t sz = 0;
     if (var->array.values != NULL) {
       for (size_t i = 0; i < dh_param(var->array.data_header); ++i) {
-        sz += str_sz((VarT *)var->array.values[i]) + 1;
+        sz += str_sz((union VarT *)var->array.values[i]) + 1;
       }
       --sz; // extra space
     }
@@ -58,11 +58,11 @@ inline size_t str_sz(union VarT *var) {
   case SEXP_T: { // tag:{a_1 a_2 ...}
     size_t sz = 0;
     if (var->sexp.tag != NULL) {
-      sz += strlen(var->sexp.tag) + 1 // tag and ':'
+      sz += strlen(var->sexp.tag) + 1; // tag and ':'
     }
     if (var->sexp.values != NULL) {
       for (size_t i = 0; i < dh_param(var->sexp.data_header); ++i) {
-        sz += str_sz((VarT *)var->sexp.values[i]) + 1;
+        sz += str_sz((union VarT *)var->sexp.values[i]) + 1;
       }
       --sz; // extra space
     }
@@ -83,10 +83,13 @@ inline char *to_str(union VarT *var, char *str, size_t max_sz) {
   case INT_T:
     snprintf(str, max_sz, "%d", var->int_t.value);
     break;
-  case CONST_STR_T:
-    strcat(str, "\"");
-    strcat(str, var->const_str.value);
-    strcat(str, "\"");
+  case BOX_T:
+    strcat(str, "<box>");
+    if (var->box.value != NULL) {
+      strcat(str, ":");
+      str += strlen(str);
+      str = to_str((union VarT *)&var->box.value, str, max_sz);
+    }
     break;
   case STR_T:
     strcat(str, "\"");
@@ -100,7 +103,7 @@ inline char *to_str(union VarT *var, char *str, size_t max_sz) {
     strcat(str, "[");
     ++str;
     for (size_t i = 0; i < dh_param(var->array.data_header); ++i) {
-      str = to_str((VarT *)var->array.values[i], str, max_sz);
+      str = to_str((union VarT *)var->array.values[i], str, max_sz);
       strcat(str, " ");
       ++str;
     }
@@ -114,7 +117,7 @@ inline char *to_str(union VarT *var, char *str, size_t max_sz) {
     strcat(str, "{");
     str += strlen(str);
     for (size_t i = 0; i < dh_param(var->sexp.data_header); ++i) {
-      str = to_str((VarT *)var->sexp.values[i], str, max_sz);
+      str = to_str((union VarT *)var->sexp.values[i], str, max_sz);
       strcat(str, " ");
       ++str;
     }
@@ -161,7 +164,7 @@ inline void f_binop(struct State *s, const char *opr) {
     z = x - y;
     break;
   case '*':
-    z - x *y;
+    z = x * y;
     break;
   case '/':
     if (y == 0) {
diff --git a/byterun/include/gc.h b/byterun/include/gc.h
new file mode 100644
index 000000000..627577c15
--- /dev/null
+++ b/byterun/include/gc.h
@@ -0,0 +1,251 @@
+// ============================================================================
+//                              GC
+// ============================================================================
+// This is an implementation of a compactifying garbage collection algorithm.
+// GC algorithm itself consists of two major stages:
+//      1. Marking roots
+//      2. Compacting stage
+// Compacting is implemented in a very similar fashion to LISP2 algorithm,
+// which is well-known.
+// Most important pieces of code to discover to understand how everything works:
+//  - void *gc_alloc (size_t): this function is basically called whenever we are
+// not able to allocate memory on the existing heap via simple bump allocator.
+//  - mark_phase(): this function will tell you everything you need to know
+// about marking. I would also recommend to pay attention to the fact that
+// marking is implemented without usage of any additional memory. Already
+// allocated space is sufficient (for details see 'void mark (void *obj)').
+//  - void compact_phase (size_t additional_size): the whole compaction phase
+// can be understood by looking at this piece of code plus couple of other
+// functions used in there. It is basically an implementation of LISP2.
+
+#ifndef __LAMA_GC__
+#define __LAMA_GC__
+
+#include "runtime_common.h"
+
+#define GET_MARK_BIT(x) (((int)(x)) & 1)
+#define SET_MARK_BIT(x) (x = (((int)(x)) | 1))
+#define IS_ENQUEUED(x) (((int)(x)) & 2)
+#define MAKE_ENQUEUED(x) (x = (((int)(x)) | 2))
+#define MAKE_DEQUEUED(x) (x = (((int)(x)) & (~2)))
+#define RESET_MARK_BIT(x) (x = (((int)(x)) & (~1)))
+// since last 2 bits are used for mark-bit and enqueued-bit and due to correct
+// alignment we can expect that last 2 bits don't influence address (they
+// should always be zero)
+#define GET_FORWARD_ADDRESS(x) (((size_t)(x)) & (~3))
+// take the last two bits as they are and make all others zero
+#define SET_FORWARD_ADDRESS(x, addr) (x = ((x & 3) | ((int)(addr))))
+// if heap is full after gc shows in how many times it has to be extended
+#define EXTRA_ROOM_HEAP_COEFFICIENT 2
+#ifdef DEBUG_VERSION
+#  define MINIMUM_HEAP_CAPACITY (8)
+#else
+#  define MINIMUM_HEAP_CAPACITY (1 << 2)
+#endif
+
+#include <stdbool.h>
+#include <stddef.h>
+
+typedef enum { ARRAY, CLOSURE, STRING, SEXP } lama_type;
+
+typedef struct {
+  size_t *current;
+} heap_iterator;
+
+typedef struct {
+  lama_type type;   // holds type of object, which fields we are iterating over
+  void     *obj_ptr;   // place to store a pointer to the object header
+  void     *cur_field;
+} obj_field_iterator;
+
+// Memory pool for linear memory allocation
+typedef struct {
+  size_t *begin;
+  size_t *end;
+  size_t *current;
+  size_t  size;
+} memory_chunk;
+
+
+// the only GC-related function that should be exposed, others are useful for tests and internal implementation
+// allocates object of the given size on the heap
+void *alloc(size_t);
+// takes number of words as a parameter
+void *gc_alloc(size_t);
+// takes number of words as a parameter
+void *gc_alloc_on_existing_heap(size_t);
+
+// specific for mark-and-compact_phase gc
+void mark (void *obj);
+void mark_phase (void);
+// marks each pointer from extra roots
+void scan_extra_roots (void);
+#ifdef LAMA_ENV
+// marks each valid pointer from global area
+void scan_global_area (void);
+#endif
+// takes number of words that are required to be allocated somewhere on the heap
+void compact_phase (size_t additional_size);
+// specific for Lisp-2 algorithm
+size_t compute_locations ();
+void   update_references (memory_chunk *);
+void   physically_relocate (memory_chunk *);
+
+
+// ============================================================================
+//                            GC extra roots
+// ============================================================================
+// Lama's program stack is continuous, i.e. it never interleaves with runtime
+// function's activation records. But some valid Lama's pointers can escape
+// into runtime. Those values (theirs stack addresses) has to be registered in
+// an auxiliary data structure called `extra_roots_pool`.
+// extra_roots_pool is a simple LIFO stack. During `pop` it compares that pop's
+// argument is equal to the current stack top.
+#define MAX_EXTRA_ROOTS_NUMBER 32
+
+typedef struct {
+  int    current_free;
+  void **roots[MAX_EXTRA_ROOTS_NUMBER];
+} extra_roots_pool;
+
+void clear_extra_roots (void);
+void push_extra_root (void **p);
+void pop_extra_root (void **p);
+
+
+// ============================================================================
+//                   Implemented in GASM: see gc_runtime.s
+// ============================================================================
+// MANDATORY TO CALL BEFORE ANY INTERACTION WITH GC (apart from cases where we
+// are working with virtual stack as happens in tests)
+void __gc_init (void);
+
+// should be called before interaction with GC in case of using in tests with
+// virtual stack, otherwise it is automatically invoked by `__gc_init`
+void __init (void);
+
+// mostly useful for tests but basically you want to call this in case you want
+// to deallocate all object allocated via GC
+extern void __shutdown (void);
+
+
+// ============================================================================
+//                    invoked from GASM: see gc_runtime.s
+// ============================================================================
+extern void        gc_test_and_mark_root (size_t **root);
+bool               is_valid_heap_pointer (const size_t *);
+static inline bool is_valid_pointer (const size_t *);
+
+
+// ============================================================================
+//                     Auxiliary functions for tests
+// ============================================================================
+#if defined(DEBUG_VERSION)
+// makes a snapshot of current objects in heap (both alive and dead), writes these ids to object_ids_buf,
+// returns number of ids dumped
+// object_ids_buf is pointer to area preallocated by user for dumping ids of objects in heap
+// object_ids_buf_size is in WORDS, NOT BYTES
+size_t objects_snapshot (int *object_ids_buf, size_t object_ids_buf_size);
+#endif
+
+
+#ifdef DEBUG_VERSION
+// essential function to mock program stack
+void set_stack (size_t stack_top, size_t stack_bottom);
+
+// function to mock extra roots (Lama specific)
+void set_extra_roots (size_t extra_roots_size, void **extra_roots_ptr);
+#endif
+
+
+// ============================================================================
+//                          Utility functions
+// ============================================================================
+// accepts pointer to the start of the region and to the end of the region
+// scans it and if it meets a pointer, it should be modified in according to forward address
+void scan_and_fix_region (memory_chunk *old_heap, void *start, void *end);
+
+// takes a pointer to an object content as an argument, returns forwarding address
+size_t get_forward_address (void *obj);
+
+// takes a pointer to an object content as an argument, sets forwarding address to value 'addr'
+void set_forward_address (void *obj, size_t addr);
+
+// takes a pointer to an object content as an argument, returns whether this object was marked as live
+bool is_marked (void *obj);
+
+// takes a pointer to an object content as an argument, marks the object as live
+void mark_object (void *obj);
+
+// takes a pointer to an object content as an argument, marks the object as dead
+void unmark_object (void *obj);
+
+// takes a pointer to an object content as an argument, returns whether this object was enqueued to the queue (which is used in mark phase)
+bool is_enqueued (void *obj);
+
+// takes a pointer to an object content as an argument, marks object as enqueued
+void make_enqueued (void *obj);
+
+// takes a pointer to an object content as an argument, unmarks object as enqueued
+void make_dequeued (void *obj);
+
+// returns iterator to an object with the lowest address
+heap_iterator heap_begin_iterator ();
+void          heap_next_obj_iterator (heap_iterator *it);
+bool          heap_is_done_iterator (heap_iterator *it);
+
+// returns correct type when pointer to actual data is passed (header is excluded)
+lama_type get_type_row_ptr (void *ptr);
+// returns correct type when pointer to an object header is passed
+lama_type get_type_header_ptr (void *ptr);
+
+// returns correct object size (together with header) of an object, ptr is pointer to an actual data is passed (header is excluded)
+size_t obj_size_row_ptr (void *ptr);
+// returns correct object size (together with header) of an object, ptr is pointer to an object header
+size_t obj_size_header_ptr (void *ptr);
+
+// returns total padding size that we need to store given object type
+size_t get_header_size (lama_type type);
+
+// returns number of bytes that are required to allocate array with 'sz' elements (header included)
+size_t array_size (size_t sz);
+
+// returns number of bytes that are required to allocate string of length 'l' (header included)
+size_t string_size (size_t len);
+
+// returns number of bytes that are required to allocate closure with 'sz-1' captured values (header included)
+size_t closure_size (size_t sz);
+
+// returns number of bytes that are required to allocate s-expression with 'members' fields (header included)
+size_t sexp_size (size_t members);
+
+// returns an iterator over object fields, obj is ptr to object header
+// (in case of s-exp, it is mandatory that obj ptr is very beginning of the object,
+// considering that now we store two versions of header in there)
+obj_field_iterator field_begin_iterator (void *obj);
+
+// returns an iterator over object fields which are actual pointers, obj is ptr to object header
+// (in case of s-exp, it is mandatory that obj ptr is very beginning of the object,
+// considering that now we store two versions of header in there)
+obj_field_iterator ptr_field_begin_iterator (void *obj);
+
+// moves the iterator to next object field
+void obj_next_field_iterator (obj_field_iterator *it);
+
+// moves the iterator to the next object field which is an actual pointer
+void obj_next_ptr_field_iterator (obj_field_iterator *it);
+
+// returns if we are done iterating over fields of the object
+bool field_is_done_iterator (obj_field_iterator *it);
+
+// ptr is pointer to the actual object content, returns pointer to the very beginning of the object (header)
+void *get_obj_header_ptr (void *ptr);
+void *get_object_content_ptr (void *header_ptr);
+void *get_end_of_obj (void *header_ptr);
+
+void *alloc_string (int len);
+void *alloc_array (int len);
+void *alloc_sexp (int members);
+void *alloc_closure (int captured);
+
+#endif
diff --git a/byterun/include/operations.h b/byterun/include/operations.h
index 0cb4bed37..f0a181a01 100644
--- a/byterun/include/operations.h
+++ b/byterun/include/operations.h
@@ -1,7 +1,7 @@
 #pragma once
 
-#include "../../runtime/gc.h"
-#include "../../runtime/runtime.h"
+#include "gc.h"
+#include "runtime.h"
 #include "types.h"
 
 #include "stdlib.h"
@@ -16,18 +16,16 @@ inline void free_var(union VarT var) {
     break;
   case INT_T:
     break;
-  case CONST_STR_T:
+  case BOX_T:
+    // pointer, do not free original object
     break;
   case STR_T:
-    free(var.str.value);
+    if (dh_param(var.str.data_header)) { // not const string
+      // free(var.str.value); // FIXME
+    }
     break;
   case CLOJURE_T:
-    if (var.list.value != NULL) {
-      free_var_ptr(to_var(var.list.value));
-    }
-    if (var.list.next != NULL) {
-      free_var_ptr(to_var(var.list.next));
-    }
+    // TODO
     break;
   case ARRAY_T:
     // dh param is size
@@ -38,8 +36,11 @@ inline void free_var(union VarT var) {
     break;
   case SEXP_T:
     // tag is const string, no need to free
-    if (var.sexp.next != NULL) {
-      // free(var.sexp.next); // FIXME
+    if (var.sexp.values != NULL) {
+      for (size_t i = 0; i < dh_param(var.sexp.data_header); ++i) {
+        free_var_ptr(to_var(var.sexp.values[i]));
+      }
+      // free(var.sexp.values); // FIXME
     }
     break;
   case FUN_T:
@@ -55,17 +56,20 @@ inline void free_var_ptr(union VarT *var) {
 
 //
 
-inline struct NilT clear_var() { return NilT{.data_header = NIL_T}; }
+inline struct NilT clear_var() {
+  struct NilT var = {.data_header = NIL_T};
+  return var;
+}
 
 // ------ put on stack ---
 
 inline void s_put_ptr(struct State *s, char *val) { // any var
-  *s->vp = (NilT *)val;
+  *s->vp = (struct NilT *)val;
   ++s->vp;
 }
 
 inline void s_put_var_ptr(struct State *s, struct NilT **val) { // any var
-  *s->vp = (NilT *)val;
+  *s->vp = (struct NilT *)val;
   ++s->vp;
 }
 
@@ -75,7 +79,7 @@ inline void s_put_var(struct State *s, struct NilT *val) { // any var
 }
 
 inline void s_put_nil(struct State *s) {
-  struct NilT *var = (NilT *)alloc(sizeof(NilT));
+  struct NilT *var = (struct NilT *)alloc(sizeof(struct NilT));
   var->data_header = NIL_T; // no param
   s_put_var(s, var);
 }
@@ -87,28 +91,35 @@ inline void s_putn_nil(struct State *s, size_t n) {
 }
 
 inline void s_put_i(struct State *s, int val) {
-  struct IntT *var = (IntT *)alloc(sizeof(IntT));
+  struct IntT *var = (struct IntT *)alloc(sizeof(struct IntT));
   var->data_header = INT_T; // no param
   var->value = val;
-  s_put_var(s, (NilT *)var);
+  s_put_var(s, (struct NilT *)var);
+}
+
+inline void s_put_box(struct State *s, struct NilT **val) {
+  struct BoxT *var = (struct BoxT *)alloc(sizeof(struct BoxT));
+  var->data_header = BOX_T; // no param
+  var->value = val;
+  s_put_var(s, (struct NilT *)var);
 }
 
 inline void s_put_const_str(struct State *s, const char *val) {
-  struct ConstStrT *var = (ConstStrT *)alloc(sizeof(ConstStrT));
-  var->data_header = CONST_STR_T; // no param
+  struct StrT *var = (struct StrT *)alloc(sizeof(struct StrT));
+  var->data_header = 0 & STR_T; // param - is const
   var->value = val;
-  s_put_var(s, (NilT *)var);
+  s_put_var(s, (struct NilT *)var);
 }
 
 inline void s_put_str(struct State *s, char *val) {
-  struct StrT *var = (StrT *)alloc(sizeof(StrT));
-  var->data_header = STR_T; // no param
+  struct StrT *var = (struct StrT *)alloc(sizeof(struct StrT));
+  var->data_header = 1 & STR_T; // param - is not const
   var->value = val;
-  s_put_var(s, (NilT *)var);
+  s_put_var(s, (struct NilT *)var);
 }
 
 inline void s_put_array(struct State *s, int sz) {
-  struct ArrayT *var = (ArrayT *)alloc(sizeof(ArrayT));
+  struct ArrayT *var = (struct ArrayT *)alloc(sizeof(struct ArrayT));
 
   if (sz < 0) {
     failure("array size < 0");
@@ -119,17 +130,17 @@ inline void s_put_array(struct State *s, int sz) {
   }
 
   var->data_header = sz & ARRAY_T;
-  var->values = (NilT **)alloc(sizeof(NilT *) * sz);
+  var->values = (struct NilT **)alloc(sizeof(struct NilT *) * sz);
 
   for (size_t i = 0; i < sz; ++i) {
     var->values[i] = NULL;
   }
-  s_put_var(s, (NilT *)var);
+  s_put_var(s, (struct NilT *)var);
 }
 
 inline union VarT *s_take_var(struct State *s);
 inline void s_put_sexp(struct State *s, const char *tag, int sz) {
-  struct SExpT *var = (SExpT *)alloc(sizeof(SExpT));
+  struct SExpT *var = (struct SExpT *)alloc(sizeof(struct SExpT));
 
   if (sz < 0) {
     failure("array size < 0");
@@ -140,14 +151,14 @@ inline void s_put_sexp(struct State *s, const char *tag, int sz) {
   }
 
   var->data_header = sz & SEXP_T;
-  var->values = (NilT **)alloc(sizeof(NilT *) * sz);
+  var->values = (struct NilT **)alloc(sizeof(struct NilT *) * sz);
 
   var->tag = tag;
 
   for (size_t i = 0; i < sz; ++i) {
-    var->values[i] = (NilT *)s_take_var(s);
+    var->values[i] = (struct NilT *)s_take_var(s);
   }
-  s_put_var(s, (NilT *)var);
+  s_put_var(s, (struct NilT *)var);
 }
 
 // inline void s_put_empty_list(struct State *s, struct NilT *first_elem) {
@@ -156,15 +167,11 @@ inline void s_put_sexp(struct State *s, const char *tag, int sz) {
 //   var->value = first_elem;
 //   var->next = NULL;
 
-//   s_put_var(s, (NilT *)var);
+//   s_put_var(s, (struct NilT *)var);
 
 //   *first_elem = clear_var();
 // }
 
-inline void s_put_sexp(struct State *s, , int args_sz) {
-  // TODO FIXME
-}
-
 // ------ take from stack ------
 
 inline union VarT *s_take_var(struct State *s) {
@@ -173,7 +180,7 @@ inline union VarT *s_take_var(struct State *s) {
   }
   --s->vp;
 
-  union VarT *ret = (VarT *)*s->vp;
+  union VarT *ret = (union VarT *)*s->vp;
   *s->vp = NULL; // clear top var
   return ret;
 }
@@ -191,7 +198,7 @@ inline void s_drop_var(struct State *s) {
     failure("drop: no var");
   }
   --s->vp;
-  free_var_ptr((VarT *)*s->vp);
+  free_var_ptr((union VarT *)*s->vp);
   *s->vp = NULL;
 }
 
@@ -210,11 +217,11 @@ inline void s_dropn_var(struct State *s, size_t n) {
 // before / after new frame added
 inline void s_enter_f(struct State *s, char *func_ip, size_t params_sz,
                       size_t locals_sz) {
-  if (params_sz > s->vp - s->stack or
-      (s->fp != NULL and params_sz > s->vp - s->fp->end)) {
+  if (params_sz > s->vp - s->stack ||
+      (s->fp != NULL && params_sz > s->vp - s->fp->end)) {
     failure("not enough parameters in stack");
   }
-  size_t frame_sz_in_ptr = sizeof(Frame) / sizeof(void *);
+  size_t frame_sz_in_ptr = sizeof(struct Frame) / sizeof(void *);
   struct Frame frame = {
       .ret = NULL, // field in frame itself
       .rp = s->ip,
@@ -225,7 +232,7 @@ inline void s_enter_f(struct State *s, char *func_ip, size_t params_sz,
   };
 
   // put frame on stack
-  s->fp = (Frame *)s->vp;
+  s->fp = (struct Frame *)s->vp;
   (*s->fp) = frame;
 
   // update stack pointer
@@ -261,7 +268,7 @@ inline void s_exit_f(struct State *s) {
 
 inline union VarT **var_by_category(struct State *s, enum VarCategory category,
                                     int id) {
-  VarT **var = NULL;
+  union VarT **var = NULL;
   switch (category) {
   case VAR_GLOBAL:
     // TODO: FIXME
@@ -277,7 +284,7 @@ inline union VarT **var_by_category(struct State *s, enum VarCategory category,
       failure("can't read local: too big id, %i >= %ul", frame_locals_sz(s->fp),
               id);
     }
-    var = (VarT **)&s->fp->locals[id];
+    var = (union VarT **)&s->fp->locals[id];
     break;
   case VAR_A:
     // TODO
diff --git a/byterun/include/runtime.h b/byterun/include/runtime.h
new file mode 100644
index 000000000..43ec9a50b
--- /dev/null
+++ b/byterun/include/runtime.h
@@ -0,0 +1,29 @@
+#pragma once
+
+#include <assert.h>
+#include <ctype.h>
+#include <errno.h>
+#include <limits.h>
+#include <regex.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <time.h>
+
+#define WORD_SIZE (CHAR_BIT * sizeof(int))
+
+inline void vfailure(char *s, va_list args) {
+  fprintf(stderr, "*** FAILURE: ");
+  vfprintf(stderr, s,
+           args); // vprintf (char *, va_list) <-> printf (char *, ...)
+  exit(255);
+}
+
+inline void failure(char *s, ...) {
+  va_list args;
+
+  va_start(args, s);
+  vfailure(s, args);
+}
diff --git a/byterun/include/runtime_common.h b/byterun/include/runtime_common.h
new file mode 100644
index 000000000..9ebae0720
--- /dev/null
+++ b/byterun/include/runtime_common.h
@@ -0,0 +1,73 @@
+#ifndef __LAMA_RUNTIME_COMMON__
+#define __LAMA_RUNTIME_COMMON__
+#include <stddef.h>
+
+// this flag makes GC behavior a bit different for testing purposes.
+//#define DEBUG_VERSION
+//#define FULL_INVARIANT_CHECKS
+
+#define STRING_TAG 0x00000001
+#define ARRAY_TAG 0x00000003
+#define SEXP_TAG 0x00000005
+#define CLOSURE_TAG 0x00000007
+#define UNBOXED_TAG 0x00000009   // Not actually a data_header; used to return from LkindOf
+
+#define LEN(x) ((x & 0xFFFFFFF8) >> 3)
+#define TAG(x) (x & 0x00000007)
+
+#define SEXP_ONLY_HEADER_SZ (sizeof(int))
+
+#ifndef DEBUG_VERSION
+#  define DATA_HEADER_SZ (sizeof(size_t) + sizeof(int))
+#else
+#  define DATA_HEADER_SZ (sizeof(size_t) + sizeof(size_t) + sizeof(int))
+#endif
+
+#define MEMBER_SIZE sizeof(int)
+
+#define TO_DATA(x) ((data *)((char *)(x) - DATA_HEADER_SZ))
+#define TO_SEXP(x) ((sexp *)((char *)(x) - DATA_HEADER_SZ))
+
+#define UNBOXED(x) (((int)(x)) & 0x0001)
+#define UNBOX(x) (((int)(x)) >> 1)
+#define BOX(x) ((((int)(x)) << 1) | 0x0001)
+
+#define BYTES_TO_WORDS(bytes) (((bytes) - 1) / sizeof(size_t) + 1)
+#define WORDS_TO_BYTES(words) ((words) * sizeof(size_t))
+
+// CAREFUL WITH DOUBLE EVALUATION!
+#define MAX(x, y) (((x) > (y)) ? (x) : (y))
+#define MIN(x, y) (((x) < (y)) ? (x) : (y))
+
+typedef struct {
+  // store tag in the last three bits to understand what structure this is, other bits are filled with
+  // other utility info (i.e., size for array, number of fields for s-expression)
+  int data_header;
+
+#ifdef DEBUG_VERSION
+  size_t id;
+#endif
+
+  // last bit is used as MARK-BIT, the rest are used to store address where object should move
+  // last bit can be used because due to alignment we can assume that last two bits are always 0's
+  size_t forward_address;
+  char   contents[0];
+} data;
+
+typedef struct {
+  // store tag in the last three bits to understand what structure this is, other bits are filled with
+  // other utility info (i.e., size for array, number of fields for s-expression)
+  int data_header;
+
+#ifdef DEBUG_VERSION
+  size_t id;
+#endif
+
+  // last bit is used as MARK-BIT, the rest are used to store address where object should move
+  // last bit can be used because due to alignment we can assume that last two bits are always 0's
+  size_t forward_address;
+  int    tag;
+  int    contents[0];
+} sexp;
+
+#endif
diff --git a/byterun/include/types.h b/byterun/include/types.h
index 24be61467..12305aecc 100644
--- a/byterun/include/types.h
+++ b/byterun/include/types.h
@@ -1,7 +1,7 @@
 #pragma once
 
-#include "../../runtime/runtime.h"
 #include "parser.h"
+#include "runtime.h"
 #include <stdint.h>
 
 // ------ Var ------
@@ -9,7 +9,7 @@
 enum Type {
   NIL_T = 0x00000000,
   INT_T = 0x00000001,
-  CONST_STR_T = 0x00000002,
+  BOX_T = 0x00000002,
   STR_T = 0x00000003,
   CLOJURE_T = 0x00000004,
   ARRAY_T = 0x00000005,
@@ -23,24 +23,24 @@ struct NilT { // AnyVarT too
 
 struct IntT {
   uint32_t data_header;
-  int32_t value; // int value => size = 1;
+  int32_t value;
 };
 
-struct ConstStrT {
+struct BoxT {
   uint32_t data_header;
-  const char *value;
+  struct NilT **value;
 };
 
 struct StrT {
-  uint32_t data_header;
-  char *value;
+  uint32_t data_header; // param - is not const (0 for const, 1 for not const)
+  const char *value;
 };
 
 struct ClojureT { // TODO
   uint32_t data_header;
   char *fun_ip;
   struct ArrayT *vars;
-}
+};
 
 // struct ListT {
 //   uint32_t data_header;
@@ -68,7 +68,7 @@ struct FunT {
 union VarT {
   struct NilT nil;
   struct IntT int_t;
-  struct ConstStrT const_str;
+  struct BoxT box;
   struct StrT str;
   struct ClojureT clojure;
   // struct ListT list;
@@ -79,7 +79,7 @@ union VarT {
 
 // same to TAG in runtime
 inline enum Type dh_type(int data_header) {
-  return (Type)(data_header & 0x00000007);
+  return (enum Type)(data_header & 0x00000007);
 }
 
 // same to LEN in runtime
@@ -141,5 +141,5 @@ inline enum VarCategory to_var_category(uint8_t category) {
   if (category > 3) {
     failure("unexpected variable category");
   }
-  return (VarCategory)category;
+  return (enum VarCategory)category;
 }
diff --git a/byterun/include/utils.h b/byterun/include/utils.h
deleted file mode 100644
index 6f70f09be..000000000
--- a/byterun/include/utils.h
+++ /dev/null
@@ -1 +0,0 @@
-#pragma once
diff --git a/byterun/src/cli.c b/byterun/src/cli.c
new file mode 100644
index 000000000..c63092638
--- /dev/null
+++ b/byterun/src/cli.c
@@ -0,0 +1,21 @@
+#include "interpreter.h"
+#include "parser.h"
+#include "runtime.h"
+
+int main(int argc, char** argv) {
+  if (argc < 2) {
+    failure("no file name provided");
+  }
+  if (argc > 2) {
+    failure("too many arguments");
+  }
+
+  
+  bytefile *f = read_file (argv[1]);
+  run(f);
+//   dump_file (stdout, f);
+
+  free(f);
+
+  return 0;
+}
diff --git a/byterun/src/gc.c b/byterun/src/gc.c
new file mode 100644
index 000000000..829a82077
--- /dev/null
+++ b/byterun/src/gc.c
@@ -0,0 +1,922 @@
+#define _GNU_SOURCE 1
+
+#include "gc.h"
+
+#include "runtime_common.h"
+
+#include <assert.h>
+#include <execinfo.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <time.h>
+#include <unistd.h>
+
+static const size_t INIT_HEAP_SIZE = MINIMUM_HEAP_CAPACITY;
+
+#ifdef DEBUG_VERSION
+size_t cur_id = 0;
+#endif
+
+static extra_roots_pool extra_roots;
+
+size_t __gc_stack_top = 0, __gc_stack_bottom = 0;
+#ifdef LAMA_ENV
+extern const size_t __start_custom_data, __stop_custom_data;
+#endif
+
+#ifdef DEBUG_VERSION
+memory_chunk heap;
+#else
+static memory_chunk heap;
+#endif
+
+#ifdef DEBUG_VERSION
+void dump_heap ();
+#endif
+
+void handler (int sig) {
+  void *array[10];
+  int   size;
+
+  // get void*'s for all entries on the stack
+  size = backtrace(array, 10);
+  fprintf(stderr, "heap size is %zu\n", heap.size);
+  backtrace_symbols_fd(array, size, STDERR_FILENO);
+  exit(1);
+}
+
+void *alloc (size_t size) {
+#ifdef DEBUG_VERSION
+  ++cur_id;
+#endif
+  size_t bytes_sz = size;
+  size            = BYTES_TO_WORDS(size);
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "allocation of size %zu words (%zu bytes): ", size, bytes_sz);
+#endif
+  void *p = gc_alloc_on_existing_heap(size);
+  if (!p) {
+    // not enough place in the heap, need to perform GC cycle
+    p = gc_alloc(size);
+  }
+  return p;
+}
+
+#ifdef FULL_INVARIANT_CHECKS
+
+// precondition: obj_content is a valid address pointing to the content of an object
+static void print_object_info (FILE *f, void *obj_content) {
+  data  *d       = TO_DATA(obj_content);
+  size_t obj_tag = TAG(d->data_header);
+  size_t obj_id  = d->id;
+  fprintf(f, "id %zu tag %zu | ", obj_id, obj_tag);
+}
+
+static void print_unboxed (FILE *f, int unboxed) { fprintf(f, "unboxed %zu | ", unboxed); }
+
+static FILE *print_stack_content (char *filename) {
+  FILE *f = fopen(filename, "w+");
+  ftruncate(fileno(f), 0);
+  fprintf(f, "Stack content:\n");
+  for (size_t *stack_ptr = (size_t *)((void *)__gc_stack_top + 4);
+       stack_ptr < (size_t *)__gc_stack_bottom;
+       ++stack_ptr) {
+    size_t value = *stack_ptr;
+    if (is_valid_heap_pointer((size_t *)value)) {
+      fprintf(f, "%p, ", (void *)value);
+      print_object_info(f, (void *)value);
+    } else {
+      print_unboxed(f, (int)value);
+    }
+    fprintf(f, "\n");
+  }
+  fprintf(f, "Stack content end.\n");
+  return f;
+}
+
+// precondition: obj_content is a valid address pointing to the content of an object
+static void objects_dfs (FILE *f, void *obj_content) {
+  void *obj_header = get_obj_header_ptr(obj_content);
+  data *obj_data   = TO_DATA(obj_content);
+  // internal mark-bit for this dfs, should be recovered by the caller
+  if ((obj_data->forward_address & 2) != 0) { return; }
+  // set this bit as 1
+  obj_data->forward_address |= 2;
+  fprintf(f, "object at addr %p: ", obj_content);
+  print_object_info(f, obj_content);
+  /*fprintf(f, "object id: %zu | ", obj_data->id);*/
+  // first cycle: print object's fields
+  for (obj_field_iterator field_it = ptr_field_begin_iterator(obj_header);
+       !field_is_done_iterator(&field_it);
+       obj_next_field_iterator(&field_it)) {
+    size_t field_value = *(size_t *)field_it.cur_field;
+    if (is_valid_heap_pointer((size_t *)field_value)) {
+      print_object_info(f, (void *)field_value);
+      /*fprintf(f, "%zu ", TO_DATA(field_value)->id);*/
+    } else {
+      print_unboxed(f, (int)field_value);
+    }
+  }
+  fprintf(f, "\n");
+  for (obj_field_iterator field_it = ptr_field_begin_iterator(obj_header);
+       !field_is_done_iterator(&field_it);
+       obj_next_field_iterator(&field_it)) {
+    size_t field_value = *(size_t *)field_it.cur_field;
+    if (is_valid_heap_pointer((size_t *)field_value)) { objects_dfs(f, (void *)field_value); }
+  }
+}
+
+FILE *print_objects_traversal (char *filename, bool marked) {
+  FILE *f = fopen(filename, "w+");
+  ftruncate(fileno(f), 0);
+  for (heap_iterator it = heap_begin_iterator(); !heap_is_done_iterator(&it);
+       heap_next_obj_iterator(&it)) {
+    void *obj_header = it.current;
+    data *obj_data   = TO_DATA(get_object_content_ptr(obj_header));
+    if ((obj_data->forward_address & 1) == marked) {
+      objects_dfs(f, get_object_content_ptr(obj_header));
+    }
+  }
+
+  // resetting bit that represent mark-bit for this internal dfs-traversal
+  for (heap_iterator it = heap_begin_iterator(); !heap_is_done_iterator(&it);
+       heap_next_obj_iterator(&it)) {
+    void *obj_header = it.current;
+    data *obj_data   = TO_DATA(get_object_content_ptr(obj_header));
+    obj_data->forward_address &= (~2);
+  }
+  fflush(f);
+
+  // print extra roots
+  for (int i = 0; i < extra_roots.current_free; i++) {
+    fprintf(f, "extra root %p %p: ", extra_roots.roots[i], *(size_t **)extra_roots.roots[i]);
+  }
+  fflush(f);
+  return f;
+}
+
+int files_cmp (FILE *f1, FILE *f2) {
+  int symbol1, symbol2;
+  int position = 0;
+  while (true) {
+    symbol1 = fgetc(f1);
+    symbol2 = fgetc(f2);
+    if (symbol1 == EOF && symbol2 == EOF) { return -1; }
+    if (symbol1 != symbol2) { return position; }
+    ++position;
+  }
+}
+
+#endif
+
+void *gc_alloc_on_existing_heap (size_t size) {
+  if (heap.current + size <= heap.end) {
+    void *p = (void *)heap.current;
+    heap.current += size;
+    memset(p, 0, size * sizeof(size_t));
+    return p;
+  }
+  return NULL;
+}
+
+void *gc_alloc (size_t size) {
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "===============================GC cycle has started\n");
+#endif
+#ifdef FULL_INVARIANT_CHECKS
+  FILE *stack_before = print_stack_content("stack-dump-before-compaction");
+  FILE *heap_before  = print_objects_traversal("before-mark", 0);
+  fclose(heap_before);
+#endif
+  mark_phase();
+#ifdef FULL_INVARIANT_CHECKS
+  FILE *heap_before_compaction = print_objects_traversal("after-mark", 1);
+#endif
+
+  compact_phase(size);
+#ifdef FULL_INVARIANT_CHECKS
+  FILE *stack_after           = print_stack_content("stack-dump-after-compaction");
+  FILE *heap_after_compaction = print_objects_traversal("after-compaction", 0);
+
+  int pos = files_cmp(stack_before, stack_after);
+  if (pos >= 0) {   // position of difference is found
+    fprintf(stderr, "Stack is modified incorrectly, see position %d\n", pos);
+    exit(1);
+  }
+  fclose(stack_before);
+  fclose(stack_after);
+  pos = files_cmp(heap_before_compaction, heap_after_compaction);
+  if (pos >= 0) {   // position of difference is found
+    fprintf(stderr, "GC invariant is broken, pos is %d\n", pos);
+    exit(1);
+  }
+  fclose(heap_before_compaction);
+  fclose(heap_after_compaction);
+#endif
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "===============================GC cycle has finished\n");
+#endif
+  return gc_alloc_on_existing_heap(size);
+}
+
+static void gc_root_scan_stack () {
+  for (size_t *p = (size_t *)(__gc_stack_top + 4); p < (size_t *)__gc_stack_bottom; ++p) {
+    gc_test_and_mark_root((size_t **)p);
+  }
+}
+
+void mark_phase (void) {
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "marking has started\n");
+  fprintf(stderr,
+          "gc_root_scan_stack has started: gc_top=%p bot=%p\n",
+          (void *)__gc_stack_top,
+          (void *)__gc_stack_bottom);
+#endif
+  gc_root_scan_stack();
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "gc_root_scan_stack has finished\n");
+  fprintf(stderr, "scan_extra_roots has started\n");
+#endif
+  scan_extra_roots();
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "scan_extra_roots has finished\n");
+  fprintf(stderr, "scan_global_area has started\n");
+#endif
+#ifdef LAMA_ENV
+  scan_global_area();
+#endif
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "scan_global_area has finished\n");
+  fprintf(stderr, "marking has finished\n");
+#endif
+}
+
+void compact_phase (size_t additional_size) {
+  size_t live_size = compute_locations();
+
+  // all in words
+  size_t next_heap_size =
+      MAX(live_size * EXTRA_ROOM_HEAP_COEFFICIENT + additional_size, MINIMUM_HEAP_CAPACITY);
+  size_t next_heap_pseudo_size = MAX(next_heap_size, heap.size);
+
+  memory_chunk old_heap = heap;
+  heap.begin            = mremap(
+      heap.begin, WORDS_TO_BYTES(heap.size), WORDS_TO_BYTES(next_heap_pseudo_size), MREMAP_MAYMOVE);
+  if (heap.begin == MAP_FAILED) {
+    perror("ERROR: compact_phase: mremap failed\n");
+    exit(1);
+  }
+  heap.end     = heap.begin + next_heap_pseudo_size;
+  heap.size    = next_heap_pseudo_size;
+  heap.current = heap.begin + (old_heap.current - old_heap.begin);
+
+  update_references(&old_heap);
+  physically_relocate(&old_heap);
+
+  heap.current = heap.begin + live_size;
+}
+
+size_t compute_locations () {
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "GC compute_locations started\n");
+#endif
+  size_t       *free_ptr  = heap.begin;
+  heap_iterator scan_iter = heap_begin_iterator();
+
+  for (; !heap_is_done_iterator(&scan_iter); heap_next_obj_iterator(&scan_iter)) {
+    void *header_ptr  = scan_iter.current;
+    void *obj_content = get_object_content_ptr(header_ptr);
+    if (is_marked(obj_content)) {
+      size_t sz = BYTES_TO_WORDS(obj_size_header_ptr(header_ptr));
+      // forward address is responsible for object header pointer
+      set_forward_address(obj_content, (size_t)free_ptr);
+      free_ptr += sz;
+    }
+  }
+
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "GC compute_locations finished\n");
+#endif
+  // it will return number of words
+  return free_ptr - heap.begin;
+}
+
+void scan_and_fix_region (memory_chunk *old_heap, void *start, void *end) {
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "GC scan_and_fix_region started\n");
+#endif
+  for (size_t *ptr = (size_t *)start; ptr < (size_t *)end; ++ptr) {
+    size_t ptr_value = *ptr;
+    // this can't be expressed via is_valid_heap_pointer, because this pointer may point area corresponding to the old
+    // heap
+    if (is_valid_pointer((size_t *)ptr_value) && (size_t)old_heap->begin <= ptr_value
+        && ptr_value <= (size_t)old_heap->current) {
+      void *obj_ptr = (void *)heap.begin + ((void *)ptr_value - (void *)old_heap->begin);
+      void *new_addr =
+          (void *)heap.begin + ((void *)get_forward_address(obj_ptr) - (void *)old_heap->begin);
+      size_t content_offset = get_header_size(get_type_row_ptr(obj_ptr));
+      *(void **)ptr         = new_addr + content_offset;
+    }
+  }
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "GC scan_and_fix_region finished\n");
+#endif
+}
+
+void scan_and_fix_region_roots (memory_chunk *old_heap) {
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "extra roots started: number of extra roots %i\n", extra_roots.current_free);
+#endif
+  for (int i = 0; i < extra_roots.current_free; i++) {
+    size_t *ptr       = (size_t *)extra_roots.roots[i];
+    size_t  ptr_value = *ptr;
+    if (!is_valid_pointer((size_t *)ptr_value)) { continue; }
+    // skip this one since it was already fixed from scanning the stack
+    if ((extra_roots.roots[i] >= (void **)__gc_stack_top
+         && extra_roots.roots[i] < (void **)__gc_stack_bottom)
+#ifdef LAMA_ENV
+        || (extra_roots.roots[i] <= (void **)&__stop_custom_data
+            && extra_roots.roots[i] >= (void **)&__start_custom_data)
+#endif
+    ) {
+#ifdef DEBUG_VERSION
+      if (is_valid_heap_pointer((size_t *)ptr_value)) {
+#  ifdef DEBUG_PRINT
+        fprintf(stderr,
+                "|\tskip extra root: %p (%p), since it points to Lama's stack top=%p bot=%p\n",
+                extra_roots.roots[i],
+                (void *)ptr_value,
+                (void *)__gc_stack_top,
+                (void *)__gc_stack_bottom);
+#  endif
+      }
+#  ifdef LAMA_ENV
+      else if ((extra_roots.roots[i] <= (void *)&__stop_custom_data
+                && extra_roots.roots[i] >= (void *)&__start_custom_data)) {
+        fprintf(
+            stderr,
+            "|\tskip extra root: %p (%p), since it points to Lama's static area stop=%p start=%p\n",
+            extra_roots.roots[i],
+            (void *)ptr_value,
+            (void *)&__stop_custom_data,
+            (void *)&__start_custom_data);
+        exit(1);
+      }
+#  endif
+      else {
+#  ifdef DEBUG_PRINT
+        fprintf(stderr,
+                "|\tskip extra root: %p (%p): not a valid Lama pointer \n",
+                extra_roots.roots[i],
+                (void *)ptr_value);
+#  endif
+      }
+#endif
+      continue;
+    }
+    if ((size_t)old_heap->begin <= ptr_value && ptr_value <= (size_t)old_heap->current) {
+      void *obj_ptr = (void *)heap.begin + ((void *)ptr_value - (void *)old_heap->begin);
+      void *new_addr =
+          (void *)heap.begin + ((void *)get_forward_address(obj_ptr) - (void *)old_heap->begin);
+      size_t content_offset = get_header_size(get_type_row_ptr(obj_ptr));
+      *(void **)ptr         = new_addr + content_offset;
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+      fprintf(stderr,
+              "|\textra root (%p) %p -> %p\n",
+              extra_roots.roots[i],
+              (void *)ptr_value,
+              (void *)*ptr);
+#endif
+    }
+  }
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "|\textra roots finished\n");
+#endif
+}
+
+void update_references (memory_chunk *old_heap) {
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "GC update_references started\n");
+#endif
+  heap_iterator it = heap_begin_iterator();
+  while (!heap_is_done_iterator(&it)) {
+    if (is_marked(get_object_content_ptr(it.current))) {
+      for (obj_field_iterator field_iter = ptr_field_begin_iterator(it.current);
+           !field_is_done_iterator(&field_iter);
+           obj_next_ptr_field_iterator(&field_iter)) {
+
+        size_t *field_value = *(size_t **)field_iter.cur_field;
+        if (field_value < old_heap->begin || field_value > old_heap->current) { continue; }
+        // this pointer should also be modified according to old_heap->begin
+        void *field_obj_content_addr =
+            (void *)heap.begin + (*(void **)field_iter.cur_field - (void *)old_heap->begin);
+        // important, we calculate new_addr very carefully here, because objects may relocate to another memory chunk
+        void *new_addr =
+            heap.begin
+            + ((size_t *)get_forward_address(field_obj_content_addr) - (size_t *)old_heap->begin);
+        // update field reference to point to new_addr
+        // since, we want fields to point to an actual content, we need to add this extra content_offset
+        // because forward_address itself is a pointer to the object's header
+        size_t content_offset = get_header_size(get_type_row_ptr(field_obj_content_addr));
+#ifdef DEBUG_VERSION
+        if (!is_valid_heap_pointer((void *)(new_addr + content_offset))) {
+#  ifdef DEBUG_PRINT
+          fprintf(stderr,
+                  "ur: incorrect pointer assignment: on object with id %d",
+                  TO_DATA(get_object_content_ptr(it.current))->id);
+#  endif
+          exit(1);
+        }
+#endif
+        *(void **)field_iter.cur_field = new_addr + content_offset;
+      }
+    }
+    heap_next_obj_iterator(&it);
+  }
+  // fix pointers from stack
+  scan_and_fix_region(old_heap, (void *)__gc_stack_top + 4, (void *)__gc_stack_bottom + 4);
+
+  // fix pointers from extra_roots
+  scan_and_fix_region_roots(old_heap);
+
+#ifdef LAMA_ENV
+  assert((void *)&__stop_custom_data >= (void *)&__start_custom_data);
+  scan_and_fix_region(old_heap, (void *)&__start_custom_data, (void *)&__stop_custom_data);
+#endif
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "GC update_references finished\n");
+#endif
+}
+
+void physically_relocate (memory_chunk *old_heap) {
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "GC physically_relocate started\n");
+#endif
+  heap_iterator from_iter = heap_begin_iterator();
+
+  while (!heap_is_done_iterator(&from_iter)) {
+    void         *obj       = get_object_content_ptr(from_iter.current);
+    heap_iterator next_iter = from_iter;
+    heap_next_obj_iterator(&next_iter);
+    if (is_marked(obj)) {
+      // Move the object from its old location to its new location relative to
+      // the heap's (possibly new) location, 'to' points to future object header
+      size_t *to = heap.begin + ((size_t *)get_forward_address(obj) - (size_t *)old_heap->begin);
+      memmove(to, from_iter.current, obj_size_header_ptr(from_iter.current));
+      unmark_object(get_object_content_ptr(to));
+    }
+    from_iter = next_iter;
+  }
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "GC physically_relocate finished\n");
+#endif
+}
+
+inline bool is_valid_heap_pointer (const size_t *p) {
+  return !UNBOXED(p) && (size_t)heap.begin <= (size_t)p && (size_t)p <= (size_t)heap.current;
+}
+
+static inline bool is_valid_pointer (const size_t *p) { return !UNBOXED(p); }
+
+static inline void queue_enqueue (heap_iterator *tail_iter, void *obj) {
+  void *tail         = tail_iter->current;
+  void *tail_content = get_object_content_ptr(tail);
+  set_forward_address(tail_content, (size_t)obj);
+  make_enqueued(obj);
+  heap_next_obj_iterator(tail_iter);
+}
+
+static inline void *queue_dequeue (heap_iterator *head_iter) {
+  void *head         = head_iter->current;
+  void *head_content = get_object_content_ptr(head);
+  void *value        = (void *)get_forward_address(head_content);
+  make_dequeued(value);
+  heap_next_obj_iterator(head_iter);
+  return value;
+}
+
+void mark (void *obj) {
+  if (!is_valid_heap_pointer(obj) || is_marked(obj)) { return; }
+
+  // TL;DR: [q_head_iter, q_tail_iter) q_head_iter -- current dequeue's victim, q_tail_iter -- place for next enqueue
+  // in forward_address of corresponding element we store address of element to be removed after dequeue operation
+  heap_iterator q_head_iter = heap_begin_iterator();
+  // iterator where we will write address of the element that is going to be enqueued
+  heap_iterator q_tail_iter = q_head_iter;
+  queue_enqueue(&q_tail_iter, obj);
+
+  // invariant: queue contains only objects that are valid heap pointers (each corresponding to content of unmarked
+  // object) also each object is in queue only once
+  while (q_head_iter.current != q_tail_iter.current) {
+    // while the queue is non-empty
+    void *cur_obj = queue_dequeue(&q_head_iter);
+    mark_object(cur_obj);
+    void *header_ptr = get_obj_header_ptr(cur_obj);
+    for (obj_field_iterator ptr_field_it = ptr_field_begin_iterator(header_ptr);
+         !field_is_done_iterator(&ptr_field_it);
+         obj_next_ptr_field_iterator(&ptr_field_it)) {
+      void *field_value = *(void **)ptr_field_it.cur_field;
+      if (!is_valid_heap_pointer(field_value) || is_marked(field_value)
+          || is_enqueued(field_value)) {
+        continue;
+      }
+      // if we came to this point it must be true that field_value is unmarked and not currently in queue
+      // thus, we maintain the invariant
+      queue_enqueue(&q_tail_iter, field_value);
+    }
+  }
+}
+
+void scan_extra_roots (void) {
+  for (int i = 0; i < extra_roots.current_free; ++i) {
+    // this dereferencing is safe since runtime is pushing correct pointers into extra_roots
+    mark(*extra_roots.roots[i]);
+  }
+}
+
+#ifdef LAMA_ENV
+void scan_global_area (void) {
+  // __start_custom_data is pointing to beginning of global area, thus all dereferencings are safe
+  for (size_t *ptr = (size_t *)&__start_custom_data; ptr < (size_t *)&__stop_custom_data; ++ptr) {
+    mark(*(void **)ptr);
+  }
+}
+#endif
+
+extern void gc_test_and_mark_root (size_t **root) {
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr,
+          "\troot = %p (%p), stack addresses: [%p, %p)\n",
+          root,
+          *root,
+          (void *)__gc_stack_top + 4,
+          (void *)__gc_stack_bottom);
+#endif
+  mark((void *)*root);
+}
+
+void __gc_init (void) {
+  __gc_stack_bottom = (size_t)__builtin_frame_address(1) + 4;
+  __init();
+}
+
+void __init (void) {
+  signal(SIGSEGV, handler);
+  size_t space_size = INIT_HEAP_SIZE * sizeof(size_t);
+
+  srandom(time(NULL));
+
+  heap.begin = mmap(
+      NULL, space_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_32BIT, -1, 0);
+  if (heap.begin == MAP_FAILED) {
+    perror("ERROR: __init: mmap failed\n");
+    exit(1);
+  }
+  heap.end     = heap.begin + INIT_HEAP_SIZE;
+  heap.size    = INIT_HEAP_SIZE;
+  heap.current = heap.begin;
+  clear_extra_roots();
+}
+
+extern void __shutdown (void) {
+  munmap(heap.begin, heap.size);
+#ifdef DEBUG_VERSION
+  cur_id = 0;
+#endif
+  heap.begin        = NULL;
+  heap.end          = NULL;
+  heap.size         = 0;
+  heap.current      = NULL;
+  __gc_stack_top    = 0;
+  __gc_stack_bottom = 0;
+}
+
+void clear_extra_roots (void) { extra_roots.current_free = 0; }
+
+void push_extra_root (void **p) {
+  if (extra_roots.current_free >= MAX_EXTRA_ROOTS_NUMBER) {
+    perror("ERROR: push_extra_roots: extra_roots_pool overflow\n");
+    exit(1);
+  }
+  assert(p >= (void **)__gc_stack_top || p < (void **)__gc_stack_bottom);
+  extra_roots.roots[extra_roots.current_free] = p;
+  extra_roots.current_free++;
+}
+
+void pop_extra_root (void **p) {
+  if (extra_roots.current_free == 0) {
+    perror("ERROR: pop_extra_root: extra_roots are empty\n");
+    exit(1);
+  }
+  extra_roots.current_free--;
+  if (extra_roots.roots[extra_roots.current_free] != p) {
+    perror("ERROR: pop_extra_root: stack invariant violation\n");
+    exit(1);
+  }
+}
+
+/* Functions for tests */
+
+#if defined(DEBUG_VERSION)
+size_t objects_snapshot (int *object_ids_buf, size_t object_ids_buf_size) {
+  size_t *ids_ptr = (size_t *)object_ids_buf;
+  size_t  i       = 0;
+  for (heap_iterator it = heap_begin_iterator();
+       !heap_is_done_iterator(&it) && i < object_ids_buf_size;
+       heap_next_obj_iterator(&it), ++i) {
+    void *header_ptr = it.current;
+    data *d          = TO_DATA(get_object_content_ptr(header_ptr));
+    ids_ptr[i]       = d->id;
+  }
+  return i;
+}
+#endif
+
+#ifdef DEBUG_VERSION
+extern char *de_hash (int);
+
+void dump_heap () {
+  size_t i = 0;
+  for (heap_iterator it = heap_begin_iterator(); !heap_is_done_iterator(&it);
+       heap_next_obj_iterator(&it), ++i) {
+    void     *header_ptr  = it.current;
+    void     *content_ptr = get_object_content_ptr(header_ptr);
+    data     *d           = TO_DATA(content_ptr);
+    lama_type t           = get_type_header_ptr(header_ptr);
+    switch (t) {
+      case ARRAY: fprintf(stderr, "of kind ARRAY\n"); break;
+      case CLOSURE: fprintf(stderr, "of kind CLOSURE\n"); break;
+      case STRING: fprintf(stderr, "of kind STRING\n"); break;
+      case SEXP:
+        fprintf(stderr, "of kind SEXP with tag %s\n", de_hash(TO_SEXP(content_ptr)->tag));
+        break;
+    }
+  }
+}
+
+void set_stack (size_t stack_top, size_t stack_bottom) {
+  __gc_stack_top    = stack_top;
+  __gc_stack_bottom = stack_bottom;
+}
+
+void set_extra_roots (size_t extra_roots_size, void **extra_roots_ptr) {
+  memcpy(extra_roots.roots, extra_roots_ptr, MIN(sizeof(extra_roots.roots), extra_roots_size));
+  clear_extra_roots();
+}
+
+#endif
+
+/* Utility functions */
+
+size_t get_forward_address (void *obj) {
+  data *d = TO_DATA(obj);
+  return GET_FORWARD_ADDRESS(d->forward_address);
+}
+
+void set_forward_address (void *obj, size_t addr) {
+  data *d = TO_DATA(obj);
+  SET_FORWARD_ADDRESS(d->forward_address, addr);
+}
+
+bool is_marked (void *obj) {
+  data *d        = TO_DATA(obj);
+  int   mark_bit = GET_MARK_BIT(d->forward_address);
+  return mark_bit;
+}
+
+void mark_object (void *obj) {
+  data *d = TO_DATA(obj);
+  SET_MARK_BIT(d->forward_address);
+}
+
+void unmark_object (void *obj) {
+  data *d = TO_DATA(obj);
+  RESET_MARK_BIT(d->forward_address);
+}
+
+bool is_enqueued (void *obj) {
+  data *d = TO_DATA(obj);
+  return IS_ENQUEUED(d->forward_address) != 0;
+}
+
+void make_enqueued (void *obj) {
+  data *d = TO_DATA(obj);
+  MAKE_ENQUEUED(d->forward_address);
+}
+
+void make_dequeued (void *obj) {
+  data *d = TO_DATA(obj);
+  MAKE_DEQUEUED(d->forward_address);
+}
+
+heap_iterator heap_begin_iterator () {
+  heap_iterator it = {.current = heap.begin};
+  return it;
+}
+
+void heap_next_obj_iterator (heap_iterator *it) {
+  void  *ptr      = it->current;
+  size_t obj_size = obj_size_header_ptr(ptr);
+  // make sure we take alignment into consideration
+  obj_size = BYTES_TO_WORDS(obj_size);
+  it->current += obj_size;
+}
+
+bool heap_is_done_iterator (heap_iterator *it) { return it->current >= heap.current; }
+
+lama_type get_type_row_ptr (void *ptr) {
+  data *data_ptr = TO_DATA(ptr);
+  return get_type_header_ptr(data_ptr);
+}
+
+lama_type get_type_header_ptr (void *ptr) {
+  int *header = (int *)ptr;
+  switch (TAG(*header)) {
+    case ARRAY_TAG: return ARRAY;
+    case STRING_TAG: return STRING;
+    case CLOSURE_TAG: return CLOSURE;
+    case SEXP_TAG: return SEXP;
+    default: {
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+      fprintf(stderr, "ERROR: get_type_header_ptr: unknown object header, cur_id=%d", cur_id);
+      raise(SIGINT);   // only for debug purposes
+#else
+#  ifdef FULL_INVARIANT_CHECKS
+#    ifdef DEBUG_PRINT
+      fprintf(stderr,
+              "ERROR: get_type_header_ptr: unknown object header, ptr is %p, tag %i, heap size is "
+              "%d cur_id=%d stack_top=%p stack_bot=%p ",
+              ptr,
+              TAG(*header),
+              heap.size,
+              cur_id,
+              (void *)__gc_stack_top,
+              (void *)__gc_stack_bottom);
+#    endif
+      FILE *heap_before_compaction = print_objects_traversal("dump_kill", 1);
+      fclose(heap_before_compaction);
+#  endif
+      kill(getpid(), SIGSEGV);
+#endif
+      exit(1);
+    }
+  }
+}
+
+size_t obj_size_row_ptr (void *ptr) {
+  data *data_ptr = TO_DATA(ptr);
+  return obj_size_header_ptr(data_ptr);
+}
+
+size_t obj_size_header_ptr (void *ptr) {
+  int len = LEN(*(int *)ptr);
+  switch (get_type_header_ptr(ptr)) {
+    case ARRAY: return array_size(len);
+    case STRING: return string_size(len);
+    case CLOSURE: return closure_size(len);
+    case SEXP: return sexp_size(len);
+    default: {
+#ifdef DEBUG_VERSION
+      fprintf(stderr, "ERROR: obj_size_header_ptr: unknown object header, cur_id=%d", cur_id);
+      raise(SIGINT);   // only for debug purposes
+#else
+      perror("ERROR: obj_size_header_ptr: unknown object header\n");
+#endif
+      exit(1);
+    }
+  }
+}
+
+size_t array_size (size_t sz) { return get_header_size(ARRAY) + MEMBER_SIZE * sz; }
+
+size_t string_size (size_t len) {
+  // string should be null terminated
+  return get_header_size(STRING) + len + 1;
+}
+
+size_t closure_size (size_t sz) { return get_header_size(CLOSURE) + MEMBER_SIZE * sz; }
+
+size_t sexp_size (size_t members) { return get_header_size(SEXP) + MEMBER_SIZE * (members + 1); }
+
+obj_field_iterator field_begin_iterator (void *obj) {
+  lama_type          type = get_type_header_ptr(obj);
+  obj_field_iterator it = {.type = type, .obj_ptr = obj, .cur_field = get_object_content_ptr(obj)};
+  switch (type) {
+    case STRING: {
+      it.cur_field = get_end_of_obj(it.obj_ptr);
+      break;
+    }
+    case CLOSURE:
+    case SEXP: {
+      it.cur_field += MEMBER_SIZE;
+      break;
+    }
+    default: break;
+  }
+  return it;
+}
+
+obj_field_iterator ptr_field_begin_iterator (void *obj) {
+  obj_field_iterator it = field_begin_iterator(obj);
+  // corner case when obj has no fields
+  if (field_is_done_iterator(&it)) { return it; }
+  if (is_valid_pointer(*(size_t **)it.cur_field)) { return it; }
+  obj_next_ptr_field_iterator(&it);
+  return it;
+}
+
+void obj_next_field_iterator (obj_field_iterator *it) { it->cur_field += MEMBER_SIZE; }
+
+void obj_next_ptr_field_iterator (obj_field_iterator *it) {
+  do {
+    obj_next_field_iterator(it);
+  } while (!field_is_done_iterator(it) && !is_valid_pointer(*(size_t **)it->cur_field));
+}
+
+bool field_is_done_iterator (obj_field_iterator *it) {
+  return it->cur_field >= get_end_of_obj(it->obj_ptr);
+}
+
+void *get_obj_header_ptr (void *ptr) {
+  lama_type type = get_type_row_ptr(ptr);
+  return ptr - get_header_size(type);
+}
+
+void *get_object_content_ptr (void *header_ptr) {
+  lama_type type = get_type_header_ptr(header_ptr);
+  return header_ptr + get_header_size(type);
+}
+
+void *get_end_of_obj (void *header_ptr) { return header_ptr + obj_size_header_ptr(header_ptr); }
+
+size_t get_header_size (lama_type type) {
+  switch (type) {
+    case STRING:
+    case CLOSURE:
+    case ARRAY:
+    case SEXP: return DATA_HEADER_SZ;
+    default: perror("ERROR: get_header_size: unknown object type\n");
+#ifdef DEBUG_VERSION
+      raise(SIGINT);   // only for debug purposes
+#endif
+      exit(1);
+  }
+}
+
+void *alloc_string (int len) {
+  data *obj        = alloc(string_size(len));
+  obj->data_header = STRING_TAG | (len << 3);
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "%p, [STRING] tag=%zu\n", obj, TAG(obj->data_header));
+#endif
+#ifdef DEBUG_VERSION
+  obj->id = cur_id;
+#endif
+  obj->forward_address = 0;
+  return obj;
+}
+
+void *alloc_array (int len) {
+  data *obj        = alloc(array_size(len));
+  obj->data_header = ARRAY_TAG | (len << 3);
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "%p, [ARRAY] tag=%zu\n", obj, TAG(obj->data_header));
+#endif
+#ifdef DEBUG_VERSION
+  obj->id = cur_id;
+#endif
+  obj->forward_address = 0;
+  return obj;
+}
+
+void *alloc_sexp (int members) {
+  sexp *obj        = alloc(sexp_size(members));
+  obj->data_header = SEXP_TAG | (members << 3);
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "%p, SEXP tag=%zu\n", obj, TAG(obj->data_header));
+#endif
+#ifdef DEBUG_VERSION
+  obj->id = cur_id;
+#endif
+  obj->forward_address = 0;
+  obj->tag             = 0;
+  return obj;
+}
+
+void *alloc_closure (int captured) {
+
+  data *obj        = alloc(closure_size(captured));
+  obj->data_header = CLOSURE_TAG | (captured << 3);
+#if defined(DEBUG_VERSION) && defined(DEBUG_PRINT)
+  fprintf(stderr, "%p, [CLOSURE] tag=%zu\n", obj, TAG(obj->data_header));
+#endif
+#ifdef DEBUG_VERSION
+  obj->id = cur_id;
+#endif
+  obj->forward_address = 0;
+  return obj;
+}
diff --git a/byterun/src/interpreter.c b/byterun/src/interpreter.c
index 1de789dd2..ce7291de9 100644
--- a/byterun/src/interpreter.c
+++ b/byterun/src/interpreter.c
@@ -1,9 +1,9 @@
-#include "../include/interpreter.h"
-#include "../include/types.h"
-#include "../include/builtin.h"
-#include "../include/operations.h"
-#include "../../runtime/runtime.h"
-#include "../../runtime/gc.h"
+#include "interpreter.h"
+#include "types.h"
+#include "builtin.h"
+#include "operations.h"
+#include "runtime.h"
+#include "gc.h"
 
 int ip_read_int(char** ip) {
   *ip += sizeof(int);
diff --git a/byterun/src/parser.c b/byterun/src/parser.c
index fda5d8653..906a79349 100644
--- a/byterun/src/parser.c
+++ b/byterun/src/parser.c
@@ -4,9 +4,9 @@
 #include <errno.h>
 #include <malloc.h>
 
-#include "../../runtime/runtime.h"
+#include "runtime.h"
 
-#include "../include/parser.h"
+#include "parser.h"
 
 void *__start_custom_data;
 void *__stop_custom_data;
@@ -284,8 +284,3 @@ void dump_file (FILE *f, bytefile *bf) {
   disassemble (f, bf);
 }
 
-int main (int argc, char* argv[]) {
-  bytefile *f = read_file (argv[1]);
-  dump_file (stdout, f);
-  return 0;
-}
diff --git a/byterun/src/types.c b/byterun/src/types.c
index c00df02fd..eb5502c29 100644
--- a/byterun/src/types.c
+++ b/byterun/src/types.c
@@ -1,4 +1,4 @@
-#include "../include/types.h"
+#include "types.h"
 
 #include <stdlib.h>
 
diff --git a/byterun/src/utils.c b/byterun/src/utils.c
deleted file mode 100644
index 8d0f08780..000000000
--- a/byterun/src/utils.c
+++ /dev/null
@@ -1 +0,0 @@
-#include "../include/utils.h"
diff --git a/byterun/xmake.lua b/byterun/xmake.lua
new file mode 100644
index 000000000..7e66280c0
--- /dev/null
+++ b/byterun/xmake.lua
@@ -0,0 +1,9 @@
+add_rules("mode.debug", "mode.release")
+
+set_languages("c23")
+
+target("byterun")
+    set_kind("binary")
+    add_includedirs("include")
+    add_headerfiles("include/*.h")
+    add_files("src/*.c")