diff --git a/TODO.md b/TODO.md
new file mode 100644
index 0000000..7d23ecd
--- /dev/null
+++ b/TODO.md
@@ -0,0 +1,25 @@
+## General refactoring
+- replace all malloc() and free() with allocator_alloc() and allocator_free()
+- replace allocating constructors with Type_init(var_ptr, ...)
+- replace Struct_free functions with Struct_destruct which will not call free() on the struct ptr
+- store in resizable structs their buffer allocators and free them with Struct_destruct()
+- check allocator_free call order
+- replace LinearAllocator with StackingAllocator when possible (in DtsodV24_deserialize)
+
+## Autoarr
+- store lenght and max_lenght inside the struct instead of calculating them by macro
+- keep Autoarr_length() and Autoarr_maxLength() to old code compatibility
+
+## Hashtable
+- store hash in KVPair
+- don't use Autoarr in Hashtable
+- make Hashtable generic struct
+
+## Unitype
+- replace UniPtrHeap with UniPtrStack
+- do something with VoidPtr ownership
+
+## String
+- add `bool zero_terminated`
+- rewrite all code to use `string` instead of `char*`
+- rewrite `StringBuilder` 
diff --git a/src/DtsodParser/DtsodV24_deserialize.c b/src/DtsodParser/DtsodV24_deserialize.c
index af2131f..da3d911 100644
--- a/src/DtsodParser/DtsodV24_deserialize.c
+++ b/src/DtsodParser/DtsodV24_deserialize.c
@@ -10,11 +10,13 @@ typedef struct DeserializeSharedData{
     char* sh_text;
     bool sh_partOfDollarList;
     bool sh_calledRecursively;
+    allocator_ptr sh_tmp_al;
 } DeserializeSharedData;
 
 #define text shared->sh_text
 #define partOfDollarList shared->sh_partOfDollarList
 #define calledRecursively shared->sh_calledRecursively
+#define tmp_al shared->sh_tmp_al
 
 
 // special func for throwing error messages about wrong characters in deserializing text
@@ -94,7 +96,7 @@ Maybe __ReadName(DeserializeSharedData* shared){
                 safethrow_wrongchar(c,;);
             return SUCCESS(UniHeapPtr(char,NULL));
         case ':':
-            return SUCCESS(UniHeapPtr(char,string_extract(nameStr)));
+            return SUCCESS(UniHeapPtr(char,string_extract(tmp_al, nameStr)));
         case '$':
             if(nameStr.length!=0)
                 safethrow_wrongchar(c,;);
@@ -111,7 +113,7 @@ Maybe __ReadName(DeserializeSharedData* shared){
 }
 #define ReadName() __ReadName(shared)
 
-Maybe __deserialize(char** _text, bool _calledRecursively);
+Maybe __deserialize(char** _text, bool _calledRecursively, allocator_ptr _tmp_al);
 Maybe __ReadValue(DeserializeSharedData* shared, bool* readingList);
 #define ReadValue(rL) __ReadValue(shared, rL)
 
@@ -119,7 +121,9 @@ Maybe __ReadValue(DeserializeSharedData* shared, bool* readingList);
 Maybe __ReadString(DeserializeSharedData* shared){
     char c;
     bool prevIsBackslash=false;
-    StringBuilder* b=StringBuilder_create();
+    StringBuilder _sb;
+    StringBuilder* b=&_sb;
+    StringBuilder_construct(b, tmp_al);
 
     while ((c=*++text)){
         if(c=='"') {
@@ -175,34 +179,34 @@ Maybe __ParseValue(DeserializeSharedData* shared, string str){
             else safethrow_wrongchar(*str.ptr,;);
         // Float64
         case 'f': {
-            char* _c=string_extract(str);
+            char* _c=string_extract(tmp_al, str);
             Unitype rez=UniFloat64(strtod(_c,NULL));
-            free(_c);
+            // allocator_free(tmp_al,_c);
             return SUCCESS(rez);
         }
         // UInt64
         case 'u': {
             u64 lu=0;
-            char* _c=string_extract(str);
+            char* _c=string_extract(tmp_al, str);
             if(sscanf(_c, IFWIN("%llu", "%lu"), &lu)!=1){
                 char err[64];
                 sprintf_s(err, sizeof(err), "can't parse to int: <%s>", _c);
-                safethrow(err,free(_c));
+                safethrow(err, /*allocator_free(tmp_al, _c)*/);
             }
-            free(_c);
+            // allocator_free(tmp_al, _c);
             return SUCCESS(UniUInt64(lu));
         }
         // Int64
         case '0': case '1': case '2': case '3': case '4':
         case '5': case '6': case '7': case '8': case '9': {
             i64 li=0;
-            char* _c=string_extract(str);
+            char* _c=string_extract(tmp_al, str);
             if(sscanf(_c, IFWIN("%lli", "%li"), &li)!=1){
                 char err[64];
                 sprintf_s(err, sizeof(err),"can't parse to int: <%s>",_c);
-                safethrow(err,free(_c));
+                // safethrow(err,allocator_free(tmp_al, _c));
             }
-            free(_c);
+            // allocator_free(tmp_al, _c);
             return SUCCESS(UniInt64(li));
         }
         // wrong type
@@ -249,7 +253,7 @@ Maybe __ReadValue(DeserializeSharedData* shared, bool* readingList){
         case '{':
             if(valueStr.length!=0) safethrow_wrongchar(c,Unitype_destruct(&value));
             ++text; // skips '{'
-            try(__deserialize(&text,true), val,Unitype_destruct(&value))
+            try(__deserialize(&text,true,tmp_al), val, Unitype_destruct(&value))
                 value=val.value;
             break;
         case '[':
@@ -282,12 +286,13 @@ Maybe __ReadValue(DeserializeSharedData* shared, bool* readingList){
 }
 
 
-Maybe __deserialize(char** _text, bool _calledRecursively) {
+Maybe __deserialize(char** _text, bool _calledRecursively, allocator_ptr _tmp_al) {
     DeserializeSharedData _shared={
         .sh_text_first=*_text,
         .sh_text=*_text,
         .sh_partOfDollarList=false,
-        .sh_calledRecursively=_calledRecursively
+        .sh_calledRecursively=_calledRecursively,
+        .sh_tmp_al=_tmp_al
     };
     DeserializeSharedData* shared=&_shared;
     Hashtable* dict=Hashtable_create();
@@ -300,7 +305,8 @@ Maybe __deserialize(char** _text, bool _calledRecursively) {
         char* nameCPtr=maybeName.value.VoidPtr;
         try(ReadValue(NULL), val, {
             Hashtable_destruct(dict);
-            free(nameCPtr);
+            // do not use, free call order is incorrect
+            // allocator_free(tmp_al, nameCPtr);
         }) {
             if(partOfDollarList){
                 partOfDollarList=false;
@@ -310,7 +316,8 @@ Maybe __deserialize(char** _text, bool _calledRecursively) {
                     list=(Autoarr(Unitype)*)lu.VoidPtr;
                     // Key is not used in that case, because it is already added
                     // to the table with the first dollar list item.
-                    free(nameCPtr);
+                    // do not use, free call order is incorrect
+                    // allocator_free(tmp_al, nameCPtr);
                 }
                 else{
                     list=Autoarr_create(Unitype,ARR_BC,ARR_BL);
@@ -328,5 +335,9 @@ Maybe __deserialize(char** _text, bool _calledRecursively) {
 }
 
 Maybe DtsodV24_deserialize(char* _text) {
-    return __deserialize(&_text, false);
+    LinearAllocator _tmp_al;
+    LinearAllocator_construct(&_tmp_al, 1024);
+    Maybe m=__deserialize(&_text, false, (allocator_ptr)&_tmp_al);
+    LinearAllocator_destruct(&_tmp_al);
+    return m;
 }
diff --git a/src/DtsodParser/DtsodV24_serialize.c b/src/DtsodParser/DtsodV24_serialize.c
index 31c1a03..16bb040 100644
--- a/src/DtsodParser/DtsodV24_serialize.c
+++ b/src/DtsodParser/DtsodV24_serialize.c
@@ -123,8 +123,13 @@ Maybe __serialize(StringBuilder* _b, u8 _tabs, Hashtable* dtsod){
 }
 
 Maybe DtsodV24_serialize(Hashtable* dtsod){
-    StringBuilder* sb=StringBuilder_create();
-    try(__serialize(sb,0,dtsod),__, StringBuilder_destruct(sb));
+    LinearAllocator _al; allocator_ptr al=(allocator_ptr)&_al;
+    LinearAllocator_construct(&_al, 512);
+    StringBuilder _sb;
+    StringBuilder* sb=&_sb;
+    StringBuilder_construct(sb, al);
+    try(__serialize(sb,0,dtsod),__, StringBuilder_destruct(sb); LinearAllocator_destruct(&_al););
     char* str=StringBuilder_build(sb).ptr;
+    LinearAllocator_destruct(&_al);
     return SUCCESS(UniHeapPtr(char, str));
 }
diff --git a/src/Filesystem/dir.c b/src/Filesystem/dir.c
index 2531468..411ce60 100644
--- a/src/Filesystem/dir.c
+++ b/src/Filesystem/dir.c
@@ -38,7 +38,7 @@ Maybe dir_create(const char* path){
     {
         char err[512];
         sprintf_s(err, sizeof(err), "can't create dicectory <%s>", path);
-        safethrow(err,;);
+        safethrow(err, LinearAllocator_destruct(&_al));
     }
     LinearAllocator_destruct(&_al);
     return MaybeNull;
diff --git a/src/Filesystem/file.c b/src/Filesystem/file.c
index c079097..4bf03fa 100644
--- a/src/Filesystem/file.c
+++ b/src/Filesystem/file.c
@@ -53,7 +53,7 @@ Maybe file_open(const char* path, FileOpenMode mode){
     LinearAllocator _al; LinearAllocator_construct(&_al, 128);
     allocator_ptr al=&_al.base;
     if(!file)
-        safethrow(cptr_concat(al, "can't open file ", (char*)path),;);
+        safethrow(cptr_concat(al, "can't open file ", (char*)path), LinearAllocator_destruct(&_al));
     LinearAllocator_destruct(&_al);
     return SUCCESS(UniHeapPtr(FileHandle,file));
 }
@@ -115,7 +115,9 @@ Maybe file_readAll(FileHandle file, char** allBytes){
     i32 rezult=0;
     char buffer[256];
     string bufStr={.ptr=buffer, .length=sizeof(buffer)};
-    StringBuilder* sb=StringBuilder_create();
+    StringBuilder _sb;
+    StringBuilder* sb=&_sb;
+    StringBuilder_construct(sb, NULL);
     u64 i=0;
     while(true){
         rezult=fgetc(file);
diff --git a/src/Filesystem/path.c b/src/Filesystem/path.c
index b3e7557..ba0e848 100644
--- a/src/Filesystem/path.c
+++ b/src/Filesystem/path.c
@@ -52,7 +52,8 @@ Maybe path_throwIfEscapes(const char* path){
     LinearAllocator _al; LinearAllocator_construct(&_al, 128);
     allocator_ptr al=&_al.base;
     if(cptr_contains(path,".."))
-        safethrow(cptr_concat(al, "path <",path,"> uses <..>, that's not allowed"),);
+        safethrow(cptr_concat(al, "path <",path,"> uses <..>, that's not allowed"),
+            LinearAllocator_destruct(&_al));
     LinearAllocator_destruct(&_al);
     return MaybeNull;
 }
@@ -83,5 +84,5 @@ char* path_basename(allocator_ptr al, char* path, bool with_extension){
         if(extIndex!=0 && extIndex!=-1)
             rezult.length=extIndex;
     }
-    return string_extract(rezult);
+    return string_extract(al, rezult);
 }
diff --git a/src/LinkedList/LinkedList_declare.h b/src/LinkedList/LinkedList_declare.h
index e7dbff4..26d2da7 100644
--- a/src/LinkedList/LinkedList_declare.h
+++ b/src/LinkedList/LinkedList_declare.h
@@ -27,7 +27,7 @@ STRUCT(LinkedList(TYPE), \
 ) \
 \
 typedef struct LinkedList_##TYPE##_functions_t { \
-    freeMembers_t freeMembers; \
+    destruct_t freeMembers; \
     void (*removePrev)(LinkedList(TYPE)* llist, LLNode(TYPE)* nextNode, bool freeRemoved); \
     void (*removeNext)(LinkedList(TYPE)* llist, LLNode(TYPE)* prevNode, bool freeRemoved); \
 } LinkedList_##TYPE##_functions_t; \
diff --git a/src/String/StringBuilder.c b/src/String/StringBuilder.c
index d1ab98f..f56c761 100644
--- a/src/String/StringBuilder.c
+++ b/src/String/StringBuilder.c
@@ -1,6 +1,6 @@
 #include "StringBuilder.h"
 
-kt_define(StringBuilder, __StringBuilder_destruct, NULL);
+kt_define(StringBuilder, (destruct_t)StringBuilder_destruct, NULL);
 
 #define BL_C 32
 #define BL_L 1024
@@ -10,7 +10,8 @@ void complete_buf(StringBuilder* b){
     if(!b->compl_bufs)
         b->compl_bufs=Autoarr_create(string,BL_C,BL_L);
     u32 len=Autoarr_length(b->curr_buf);
-    if(!len) return;
+    if(len==0)
+        return;
     string str={.length=len, .ptr=malloc(len)};
     u32 i=0;
     Autoarr_foreach(b->curr_buf, c,
@@ -21,27 +22,19 @@ void complete_buf(StringBuilder* b){
     b->curr_buf=Autoarr_create(i8,BL_C,BL_L);
 }
 
-void try_complete_buf(StringBuilder* b){
-    if(b->curr_buf->chunks_count==BL_C)
-        complete_buf(b);
-}
 
-
-StringBuilder* StringBuilder_create(){
-    StringBuilder* b=malloc(sizeof(StringBuilder));
+void StringBuilder_construct(StringBuilder* b, allocator_ptr external_al){
+    InternalAllocator_setExternalOrConstruct(b, external_al, LinearAllocator, 1024);
     b->compl_bufs=NULL;
     b->curr_buf=Autoarr_create(i8,BL_C,BL_L);
-    return b;
 }
 
-void __StringBuilder_destruct(void* _b){
-    StringBuilder* b=_b;
-    if(b->compl_bufs) Autoarr_destruct(b->compl_bufs, true);
-    Autoarr_destruct(b->curr_buf, true);
-}
 void StringBuilder_destruct(StringBuilder* b){
-    __StringBuilder_destruct(b);
-    free(b);
+    if(b->compl_bufs)
+        Autoarr_destruct(b->compl_bufs, true);
+    Autoarr_destruct(b->curr_buf, true);
+    if(InternalAllocator_isInternal(b))
+        LinearAllocator_destruct((LinearAllocator*)InternalAllocator_getPtr(b));
 }
 
 string StringBuilder_build(StringBuilder* b){
@@ -52,11 +45,10 @@ string StringBuilder_build(StringBuilder* b){
     );
     string str= { .length=len, .ptr=malloc(len+1) };
     str.ptr[len]='\0';
-    u32 i=0;
+    u32 l=0;
     Autoarr_foreach(b->compl_bufs, cs,
-        for(u32 n=0;n<cs.length;n++)
-            str.ptr[i++]=cs.ptr[n];
-        free(cs.ptr);
+        memcpy(str.ptr+l, cs.ptr, cs.length);
+        l+=cs.length;
     );
     StringBuilder_destruct(b);
     return str;
@@ -75,14 +67,15 @@ void StringBuilder_rmchar(StringBuilder* b){
 
 
 void StringBuilder_append_char(StringBuilder* b, char c){
-    try_complete_buf(b);
+    if(b->curr_buf->chunks_count==BL_C)
+        complete_buf(b);
     Autoarr_add(b->curr_buf,c);
 }
 
-
 void StringBuilder_append_string(StringBuilder* b, string s){
     complete_buf(b);
-    Autoarr_add(b->compl_bufs, string_copy(s));
+    // TODO remove copying
+    Autoarr_add(b->compl_bufs, string_copy(InternalAllocator_getPtr(b), s));
 }
 
 void StringBuilder_append_cptr(StringBuilder* b, char* s){
@@ -90,16 +83,10 @@ void StringBuilder_append_cptr(StringBuilder* b, char* s){
         .ptr=s,
         .length=cptr_length(s)
     };
-    StringBuilder_append_string(b,str);
-}
-
-void curr_buf_add_string(StringBuilder* b, string s){
-    for(u32 i=0; i<s.length; i++)
-        Autoarr_add(b->curr_buf,s.ptr[i]);
+    StringBuilder_append_string(b, str);
 }
 
 void StringBuilder_append_i64(StringBuilder* b, i64 a){
-    try_complete_buf(b);
     u8 i=0;
     if(a==0){
         Autoarr_add(b->curr_buf,'0');
@@ -114,13 +101,11 @@ void StringBuilder_append_i64(StringBuilder* b, i64 a){
         buf[i++]='0'+a%10;
         a/=10;
     }
-    string rev=string_reverse((string){buf,i});
-    curr_buf_add_string(b,rev);
-    free(rev.ptr);
+    string rev=string_reverse(InternalAllocator_getPtr(b), (string){buf,i});
+    StringBuilder_append_string(b, rev);
 }
 
 void StringBuilder_append_u64(StringBuilder* b, u64 a){
-    try_complete_buf(b);
     u8 i=0;
     if(a==0){
         Autoarr_add(b->curr_buf,'0');
@@ -131,14 +116,12 @@ void StringBuilder_append_u64(StringBuilder* b, u64 a){
         buf[i++]='0'+a%10;
         a/=10;
     }
-    string rev=string_reverse((string){buf,i});
-    curr_buf_add_string(b,rev);
-    free(rev.ptr);
+    string rev=string_reverse(InternalAllocator_getPtr(b), (string){buf,i});
+    StringBuilder_append_string(b, rev);
 }
 
 void StringBuilder_append_f64(StringBuilder* b, f64 a){
-    try_complete_buf(b);
     char buf[32];
     sprintf_s(buf, sizeof(buf), "%lf", a);
-    curr_buf_add_string(b, (string){.ptr=buf, .length=cptr_length(buf)});
+    StringBuilder_append_string(b, (string){.ptr=buf, .length=cptr_length(buf)});
 }
diff --git a/src/String/StringBuilder.h b/src/String/StringBuilder.h
index 2d0c694..181f249 100644
--- a/src/String/StringBuilder.h
+++ b/src/String/StringBuilder.h
@@ -8,17 +8,19 @@ extern "C" {
 #include "string.h"
 
 STRUCT(StringBuilder,
+    InternalAllocator_decl(LinearAllocator);
 	Autoarr(string)* compl_bufs;
 	Autoarr(i8)* curr_buf;
 )
 
-StringBuilder* StringBuilder_create(void);
+///@param external_al if null, creates internal allocator 
+void StringBuilder_construct(StringBuilder* b, allocator_ptr external_al);
 void StringBuilder_destruct(StringBuilder* b);
-void __StringBuilder_destruct(void* b);
+
 // Joins all strings from compl_bufs.
 // Returns zero-terminated string.
-// No need to call string_extract()!
-// Frees StringBuilder.
+// No need to call string_extract!
+// Destructs StringBuilder.
 string StringBuilder_build(StringBuilder* b);
 // removes last char
 void StringBuilder_rmchar(StringBuilder* b);
diff --git a/src/String/string.c b/src/String/string.c
index 5f55ec9..676bb43 100644
--- a/src/String/string.c
+++ b/src/String/string.c
@@ -4,32 +4,32 @@ kt_define(string, NULL, NULL);
 Autoarr_define(string, false);
 
 // copies str content to new char pointer value (adding '\0' at the end)
-char* string_extract(string str){
+char* string_extract(allocator_ptr al, string str){
     if(str.length==0) return NULL;
-    char* cptr=malloc(str.length*sizeof(char)+1);
+    char* cptr=allocator_alloc(al, str.length+1);
+    memcpy(cptr, str.ptr, str.length);
     cptr[str.length]=0;
-    while(str.length-->0)
-        cptr[str.length]=str.ptr[str.length];
     return cptr;
 }
-
+    
 // copies src.ptr content to new string and adds \0 at the end
-string string_copy(string src){
+string string_copy(allocator_ptr al, string src){
     if(!src.ptr)
-        return src;
+        throw(ERR_NULLPTR);
     string nstr;
     nstr.length=src.length;
-    nstr.ptr=malloc(nstr.length+1);
-    for(u32 i=0;i<nstr.length;i++)
-        nstr.ptr[i]=src.ptr[i];
+    nstr.ptr=allocator_alloc(al, nstr.length+1);
+    memcpy(nstr.ptr, src.ptr, nstr.length);
     nstr.ptr[nstr.length]='\0';
     return nstr;
 }
 
 // compares two strings, NullPtr-friendly
 bool string_compare(string str0, string str1){
-    if(str0.length!=str1.length) return false;
-    if(!str0.ptr) return str1.ptr ? false : true;
+    if(str0.length!=str1.length)
+        return false;
+    if(!str0.ptr)
+        return str1.ptr ? false : true;
     else if(!str1.ptr) return false;
     while(str0.length-->0)
         if(*str0.ptr++ != *str1.ptr++)
@@ -38,9 +38,12 @@ bool string_compare(string str0, string str1){
 }
 
 // creates new string which is reversed variant of <s>
-string string_reverse(string s){
-    if(s.length==0) return s;
-    string r={malloc(s.length), s.length};
+string string_reverse(allocator_ptr al, string s){
+    if(s.length==0) 
+        return s;
+    string r;
+    r.ptr=allocator_alloc(al, s.length);
+    r.length=s.length;
     for(u32 i=0; i<s.length; i++)
         r.ptr[i]=s.ptr[s.length-i-1];
     return r;
diff --git a/src/String/string.h b/src/String/string.h
index 2f84b86..f14aa0d 100644
--- a/src/String/string.h
+++ b/src/String/string.h
@@ -22,16 +22,16 @@ static const string stringNull={NULL,0};
 #define string_fromCptr(CPTR) (string){ .ptr=CPTR, .length=cptr_length(CPTR) }
 
 // copies str content to new char pointer value (adding '\0' at the end)
-char* string_extract(string str);
+char* string_extract(allocator_ptr al, string str);
 
 // copies src.ptr content to new string and adds \0 at the end
-string string_copy(string src);
+string string_copy(allocator_ptr al, string src);
 
 // compares two strings, NullPtr-friendly
 bool string_compare(string str0, string str1);
 
 // creates new string which is reversed variant of <s>
-string string_reverse(string s);
+string string_reverse(allocator_ptr al, string s);
 
 #if __cplusplus
 }
diff --git a/src/base/cptr.c b/src/base/cptr.c
index 071332e..22ce87c 100644
--- a/src/base/cptr.c
+++ b/src/base/cptr.c
@@ -191,7 +191,9 @@ char* cptr_replaceCharIn(allocator_ptr al, const char* src, char c_old, char c_n
 }
 
 char* cptr_replaceIn(allocator_ptr al, const char* src, const char* str_old, const char* str_new, u32 startIndex, u32 seekLength){
-    StringBuilder* sb=StringBuilder_create();
+    StringBuilder _sb;
+    StringBuilder* sb=&_sb;
+    StringBuilder_construct(sb, al);
     const u32 str_old_len=cptr_length(str_old);
     const u32 str_new_len=cptr_length(str_new);
     i32 i=startIndex;
diff --git a/src/base/memory/LinearAllocator.c b/src/base/memory/LinearAllocator.c
index 9641962..5129262 100644
--- a/src/base/memory/LinearAllocator.c
+++ b/src/base/memory/LinearAllocator.c
@@ -81,4 +81,4 @@ void LinearAllocator_construct(LinearAllocator* self, size_t starting_size){
     self->chunks[0]=chunk_alloc(starting_size, 0);
 }
 
-kt_define(LinearAllocator, (freeMembers_t)LinearAllocator_destruct, NULL)
+kt_define(LinearAllocator, (destruct_t)LinearAllocator_destruct, NULL)
diff --git a/src/base/memory/StackingAllocator.c b/src/base/memory/StackingAllocator.c
index 3ca44aa..b8ce0c9 100644
--- a/src/base/memory/StackingAllocator.c
+++ b/src/base/memory/StackingAllocator.c
@@ -55,4 +55,4 @@ void StackingAllocator_construct(StackingAllocator* self, size_t starting_size){
     self->allocations_count=0;
 }
 
-kt_define(StackingAllocator, (freeMembers_t)StackingAllocator_destruct, NULL)
+kt_define(StackingAllocator, (destruct_t)StackingAllocator_destruct, NULL)
diff --git a/src/base/memory/memory.h b/src/base/memory/memory.h
index 78c91f8..9912e27 100644
--- a/src/base/memory/memory.h
+++ b/src/base/memory/memory.h
@@ -4,3 +4,36 @@
 #define memory_align sizeof(void*)
 // adds padding if memory_align if N isn't a multiple of memory_aligh
 #define add_padding(N) (N + (N%memory_align != 0)*(memory_align - N%memory_align)) 
+
+
+///////////////////////////////////////////
+//           NOT AN ALLOCATOR            //
+///////////////////////////////////////////
+// Macros to embed internal allocator    //
+// into some collection struct.          // 
+///////////////////////////////////////////
+
+/// call this macro inside struct declaration
+#define InternalAllocator_decl(AL_TYPE) \
+    AL_TYPE _internal_al; \
+    allocator_ptr _internal_al_ptr;
+
+/// get pointer to allocator
+#define InternalAllocator_getPtr(STRUCT_PTR) (STRUCT_PTR->_internal_al_ptr)
+
+/// true if allocator is stored inside the struct, otherwise false
+#define InternalAllocator_isInternal(STRUCT_PTR) (bool)(STRUCT_PTR->_internal_al_ptr == (allocator_ptr)&STRUCT_PTR->_internal_al)
+
+/// set ptr to external allocator
+#define InternalAllocator_setExternal(STRUCT_PTR, EXT_AL_PTR) (STRUCT_PTR->_internal_al_ptr = EXT_AL_PTR);
+
+/// create internal allocator and set ptr to it
+#define InternalAllocator_construct(STRUCT_PTR, TYPE, CTOR_ARGS...) ({ \
+    TYPE##_construct(&STRUCT_PTR->_internal_al, CTOR_ARGS); \
+    STRUCT_PTR->_internal_al_ptr = (allocator_ptr)&STRUCT_PTR->_internal_al; \
+})
+
+/// if EXT_AL_PTR isn't null, set external allocator, otherwise create new
+#define InternalAllocator_setExternalOrConstruct(STRUCT_PTR, EXT_AL_PTR, TYPE, CTOR_ARGS...) \
+    if(EXT_AL_PTR!=NULL) InternalAllocator_setExternal(STRUCT_PTR, EXT_AL_PTR) \
+    else InternalAllocator_construct(STRUCT_PTR, TYPE, CTOR_ARGS)
diff --git a/src/base/type_system/ktDescriptor.h b/src/base/type_system/ktDescriptor.h
index e492cf1..7a72a31 100644
--- a/src/base/type_system/ktDescriptor.h
+++ b/src/base/type_system/ktDescriptor.h
@@ -31,14 +31,14 @@ extern "C" {
         .toString=TOSTRING_F \
     };
 
-typedef void (*freeMembers_t)(void*);
+typedef void (*destruct_t)(void*);
 typedef char* (*toString_t)(allocator_ptr al, void* obj, u32 fmt);
 
 STRUCT(ktDescriptor,
     char* name;
     ktid id;
     u16 size;
-    freeMembers_t freeMembers; // NULL or function which frees all struct members
+    destruct_t freeMembers; // NULL or function which frees all struct members
     toString_t toString; // NULL or function which generates string representaion of object
 )
 
diff --git a/src/base/type_system/typedef_macros.h b/src/base/type_system/typedef_macros.h
index ccaab8d..6b2a299 100644
--- a/src/base/type_system/typedef_macros.h
+++ b/src/base/type_system/typedef_macros.h
@@ -8,6 +8,10 @@
     ENUM_MEMBERS \
 } __attribute__((__packed__)) ENUM_NAME;
 
+#define PACKED_STRUCT(STRUCT_NAME, STRUCT_MEMBERS...) typedef struct STRUCT_NAME { \
+    STRUCT_MEMBERS \
+} __attribute__((__packed__)) STRUCT_NAME;
+
 #define STRUCT(STRUCT_NAME, STRUCT_MEMBERS...) typedef struct STRUCT_NAME STRUCT_NAME; \
 typedef struct STRUCT_NAME { \
     STRUCT_MEMBERS \
diff --git a/src/base/type_system/unitype.c b/src/base/type_system/unitype.c
index 79fd2d7..986c8d6 100644
--- a/src/base/type_system/unitype.c
+++ b/src/base/type_system/unitype.c
@@ -6,7 +6,7 @@ char *__Unitype_toString(allocator_ptr al, void *_u, u32 fmt)
     return Unitype_toString(al, *(Unitype *)_u, fmt);
 }
 
-kt_define(Unitype, (freeMembers_t)Unitype_destruct, __Unitype_toString);
+kt_define(Unitype, (destruct_t)Unitype_destruct, __Unitype_toString);
 
 void Unitype_destruct(Unitype* u)
 {
diff --git a/src/kprint/kprint.c b/src/kprint/kprint.c
index a700dcc..d483e83 100644
--- a/src/kprint/kprint.c
+++ b/src/kprint/kprint.c
@@ -47,13 +47,15 @@ Maybe check_argsN(u8 n){
 Maybe __ksprint(allocator_ptr al, u8 n, kp_fmt* formats, __kp_value_union* objects){
     try(check_argsN(n), _,;);
     n/=2;
-    StringBuilder* strb=StringBuilder_create();
+    StringBuilder _sb;
+    StringBuilder* sb=&_sb;
+    StringBuilder_construct(sb, al);
     for(u8 i=0; i<n; i++){
         try(__next_toString(al, formats[i], &objects[i]),mStr,;);
-        StringBuilder_append_cptr(strb, mStr.value.VoidPtr);
+        StringBuilder_append_cptr(sb, mStr.value.VoidPtr);
         allocator_free(al, mStr.value.VoidPtr);
     }
-    char* rezult=StringBuilder_build(strb).ptr;
+    char* rezult=StringBuilder_build(sb).ptr;
     return SUCCESS(UniHeapPtr(char, rezult));
 }
 
@@ -173,17 +175,19 @@ void kprint_setColor(kp_fmt f){
     ktDescriptor* type=ktDescriptor_get(format.typeId);
     if(!type->toString)
         safethrow("type descriptor doesnt have toString() func",;);
-    StringBuilder* strb=StringBuilder_create();
-    StringBuilder_append_char(strb, '[');
+    StringBuilder _sb;
+    StringBuilder* sb=&_sb;
+    StringBuilder_construct(sb, al);
+    StringBuilder_append_char(sb, '[');
     for (u16 e=1; e<count; e++){
-        StringBuilder_append_char(strb, ' ');
+        StringBuilder_append_char(sb, ' ');
         char* elStr=type->toString(array+type->size*e, &format);
-        StringBuilder_append_cptr(strb, elStr);
-        StringBuilder_append_char(strb, ',');
+        StringBuilder_append_cptr(sb, elStr);
+        StringBuilder_append_char(sb, ',');
     }
-    StringBuilder_rmchar(strb);
-    StringBuilder_append_char(strb, ' ');
-    StringBuilder_append_char(strb, ']');
+    StringBuilder_rmchar(sb);
+    StringBuilder_append_char(sb, ' ');
+    StringBuilder_append_char(sb, ']');
 } */
 
 static const char* _kp_colorNames[16]={
diff --git a/tests/test_safethrow.c b/tests/test_safethrow.c
index 3cc185c..f961aab 100644
--- a/tests/test_safethrow.c
+++ b/tests/test_safethrow.c
@@ -5,8 +5,7 @@ Maybe dont_throw(){
 }
 
 Maybe throw_error(){
-    char* k=malloc(64);
-    safethrow("test exception",free(k));
+    safethrow("test exception", kprintf("\e[94on_safethrow_free called\n"));
 }
 
 Maybe throw_errcode(){
diff --git a/tests/test_string.c b/tests/test_string.c
index d59c12d..8914cac 100644
--- a/tests/test_string.c
+++ b/tests/test_string.c
@@ -4,11 +4,14 @@
 void test_string(){
     optime(__func__,1,
         kprintf("\e[96m-------------[test_string]------------\n");
+        LinearAllocator _al;
+        LinearAllocator_construct(&_al, 64);
+        allocator_ptr al=(allocator_ptr)&_al;
         char c[]="0123456789abcdef";
         string s={.ptr=c, .length=cptr_length(c)};
         if(s.length!=sizeof(c)-1) throw("string created with incorrect length");
-        char* p=string_extract(s);
-        kprintf("\e[94mstring_extract() -> \e[92m\"%s\"\n",p);
-        free(p);
+        char* p=string_extract(al, s);
+        kprintf("\e[94mstring_extract -> \e[92m\"%s\"\n",p);
+        LinearAllocator_destruct(&_al);
     );
 }