diff --git a/CMakeLists.txt b/CMakeLists.txt
index 70cb8b8d..c7fc7c94 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -79,7 +79,7 @@ else()
   set(HAVE_SSE42 FALSE)
 endif()
 
-set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
 set(CMAKE_CXX_EXTENSIONS FALSE)
 
diff --git a/common/delay.h b/common/delay.h
index 2d5f37b2..3df8e7d8 100644
--- a/common/delay.h
+++ b/common/delay.h
@@ -18,7 +18,6 @@
 */
 #pragma once
 
-#include "absl/strings/internal/str_format/parser.h"
 #include "td/actor/actor.h"
 
 namespace ton {
diff --git a/crypto/test/test-db.cpp b/crypto/test/test-db.cpp
index c1e4c2ce..7ac1096f 100644
--- a/crypto/test/test-db.cpp
+++ b/crypto/test/test-db.cpp
@@ -62,6 +62,7 @@
 #include "vm/dict.h"
 
 #include <numeric>
+#include <optional>
 
 namespace vm {
 
@@ -2010,7 +2011,7 @@ TEST(TonDb, CompactArrayOld) {
     SCOPE_EXIT {
       ton_db->commit_transaction(std::move(txn));
     };
-    auto smart = txn->begin_smartcontract("");
+    auto smart = txn->begin_smartcontract();
     SCOPE_EXIT {
       txn->commit_smartcontract(std::move(smart));
     };
@@ -2037,7 +2038,7 @@ TEST(TonDb, CompactArrayOld) {
     SCOPE_EXIT {
       ton_db->commit_transaction(std::move(txn));
     };
-    auto smart = txn->begin_smartcontract("");
+    auto smart = txn->begin_smartcontract();
     //smart->validate_meta();
     SCOPE_EXIT {
       txn->commit_smartcontract(std::move(smart));
@@ -2058,7 +2059,7 @@ TEST(TonDb, CompactArrayOld) {
     SCOPE_EXIT {
       ton_db->abort_transaction(std::move(txn));
     };
-    auto smart = txn->begin_smartcontract("");
+    auto smart = txn->begin_smartcontract();
     SCOPE_EXIT {
       txn->abort_smartcontract(std::move(smart));
     };
@@ -2219,7 +2220,7 @@ TEST(TonDb, CellStat) {
     ASSERT_EQ(stat.cells, new_stat.get_stat().cells);
     ASSERT_EQ(stat.bits, new_stat.get_stat().bits);
 
-    CHECK(usage_tree.unique());
+    CHECK(usage_tree.use_count() == 1);
     usage_tree.reset();
     td::Ref<vm::Cell> C, BC, C_proof;
     std::shared_ptr<vm::CellUsageTree> usage_tree_B;
diff --git a/crypto/vm/cells/CellHash.h b/crypto/vm/cells/CellHash.h
index 2810ad46..9435675f 100644
--- a/crypto/vm/cells/CellHash.h
+++ b/crypto/vm/cells/CellHash.h
@@ -76,7 +76,7 @@ struct CellHash {
 
 inline size_t cell_hash_slice_hash(td::Slice hash) {
   // use offset 8, because in db keys are grouped by first bytes.
-  return td::as<size_t>(hash.ubegin() + 8);
+  return td::as<size_t>(hash.substr(8, 8).ubegin());
 }
 namespace std {
 template <>
diff --git a/crypto/vm/db/InMemoryBagOfCellsDb.cpp b/crypto/vm/db/InMemoryBagOfCellsDb.cpp
index 950233b3..aa8f7910 100644
--- a/crypto/vm/db/InMemoryBagOfCellsDb.cpp
+++ b/crypto/vm/db/InMemoryBagOfCellsDb.cpp
@@ -14,6 +14,8 @@
 #include "td/utils/HashMap.h"
 #include "td/utils/HashSet.h"
 
+#include <optional>
+
 #if TD_PORT_POSIX
 #include <sys/mman.h>
 #include <unistd.h>
@@ -98,7 +100,7 @@ class ArenaPrunnedCellCreator : public ExtCellCreator {
       }
 #else
       static std::unique_ptr<char, Deleter> alloc() {
-        auto ptr = reinterpret_cast<char *>(malloc(batch_size)));
+        auto ptr = reinterpret_cast<char *>(malloc(batch_size));
         CHECK(ptr != nullptr);
         return std::unique_ptr<char, Deleter>(ptr);
       }
@@ -292,7 +294,7 @@ struct CellInfoHashTableDense {
   }
   template <class Iterator>
   void init_from(Iterator begin, Iterator end) {
-    auto size = std::distance(begin, end);
+    auto size = td::narrow_cast<size_t>(std::distance(begin, end));
     dense_ht_buckets_ = std::max(size_t(1), size_t(size / 8));
 
     std::vector<size_t> offsets(dense_ht_buckets_ + 2);
@@ -438,16 +440,16 @@ class CellStorage {
       add_stat("ht.size", size);
       add_stat("ht.load", double(size) / std::max(1.0, double(capacity)));
     }
-    CHECK(stats.roots_total_count == local_roots_.size());
+    CHECK(td::narrow_cast<size_t>(stats.roots_total_count) == local_roots_.size());
     return stats;
   }
   void apply_stats_diff(DynamicBagOfCellsDb::Stats diff) {
     auto unique_access = local_access_.lock();
     stats_.apply_diff(diff);
-    CHECK(stats_.roots_total_count == local_roots_.size());
+    CHECK(td::narrow_cast<size_t>(stats_.roots_total_count) == local_roots_.size());
     size_t cells_count{0};
     for_each_bucket(0, [&](size_t bucket_id, auto &bucket) { cells_count += bucket.infos_.size(); });
-    CHECK(stats_.cells_total_count == cells_count);
+    CHECK(td::narrow_cast<size_t>(stats_.cells_total_count) == cells_count);
   }
 
   td::Result<Ref<DataCell>> load_cell(const CellHash &hash) const {
@@ -541,8 +543,8 @@ class CellStorage {
     DefaultPrunnedCellCreator default_pc_creator;
 
     auto timer = td::Timer();
-    size_t cell_count{0};
-    size_t desc_count{0};
+    td::int64 cell_count{0};
+    td::int64 desc_count{0};
     if (options.use_less_memory_during_creation) {
       auto [new_cell_count, new_desc_count] = parallel_scan_cells(
           default_pc_creator, options.use_arena,
diff --git a/crypto/vm/db/TonDb.h b/crypto/vm/db/TonDb.h
index 8779f1b2..6cd8aa4f 100644
--- a/crypto/vm/db/TonDb.h
+++ b/crypto/vm/db/TonDb.h
@@ -113,7 +113,8 @@ class TonDbTransactionImpl;
 using TonDbTransaction = std::unique_ptr<TonDbTransactionImpl>;
 class TonDbTransactionImpl {
  public:
-  SmartContractDb begin_smartcontract(td::Slice hash = {});
+
+  SmartContractDb begin_smartcontract(td::Slice hash = std::string(32, '\0'));
 
   void commit_smartcontract(SmartContractDb txn);
   void commit_smartcontract(SmartContractDiff txn);
diff --git a/tdactor/td/actor/core/ActorTypeStat.cpp b/tdactor/td/actor/core/ActorTypeStat.cpp
index e241dd56..8f50fa9c 100644
--- a/tdactor/td/actor/core/ActorTypeStat.cpp
+++ b/tdactor/td/actor/core/ActorTypeStat.cpp
@@ -2,12 +2,24 @@
 #include "td/actor/core/ActorTypeStat.h"
 #include "td/actor/core/Scheduler.h"
 #include "td/utils/port/thread_local.h"
-#include <cxxabi.h>
 #include <set>
 #include <map>
 #include <mutex>
 #include <typeindex>
 #include <typeinfo>
+#include <optional>
+#include "td/utils/port/platform.h"
+
+#ifdef __has_include
+#if __has_include(<cxxabi.h>)
+#include <cxxabi.h>
+#define CXXABI_AVAILABLE 1
+#else
+#define CXXABI_AVAILABLE 0
+#endif
+#else
+#define CXXABI_AVAILABLE 0
+#endif
 
 namespace td {
 namespace actor {
@@ -82,6 +94,7 @@ ActorTypeStatRef ActorTypeStatManager::get_actor_type_stat(td::uint32 id, Actor
 }
 
 std::string ActorTypeStatManager::get_class_name(const char *name) {
+#if CXXABI_AVAILABLE
   int status;
   char *real_name = abi::__cxa_demangle(name, nullptr, nullptr, &status);
   if (status < 0) {
@@ -91,6 +104,9 @@ std::string ActorTypeStatManager::get_class_name(const char *name) {
   std::string result = real_name;
   std::free(real_name);
   return result;
+#else
+  return name;
+#endif
 }
 
 ActorTypeStats ActorTypeStatManager::get_stats(double inv_ticks_per_second) {
diff --git a/tdutils/td/utils/port/Clocks.cpp b/tdutils/td/utils/port/Clocks.cpp
index 59e80f61..7e27d51a 100644
--- a/tdutils/td/utils/port/Clocks.cpp
+++ b/tdutils/td/utils/port/Clocks.cpp
@@ -22,6 +22,10 @@
 #include <ctime>
 
 namespace td {
+int64 Clocks::monotonic_nano() {
+  auto duration = std::chrono::steady_clock::now().time_since_epoch();
+  return std::chrono::duration_cast<std::chrono::nanoseconds>(duration).count();
+}
 
 double Clocks::monotonic() {
   // TODO write system specific functions, because std::chrono::steady_clock is steady only under Windows
diff --git a/tdutils/td/utils/port/Clocks.h b/tdutils/td/utils/port/Clocks.h
index 7640e216..b2054365 100644
--- a/tdutils/td/utils/port/Clocks.h
+++ b/tdutils/td/utils/port/Clocks.h
@@ -22,20 +22,22 @@
 namespace td {
 
 struct Clocks {
+  static int64 monotonic_nano();
+
   static double monotonic();
 
   static double system();
 
   static int tz_offset();
 
-#if defined(__i386__)
-  static __inline__ td::uint64 rdtsc(void) {
+#if defined(__i386__) or defined(__M_IX86)
+  static uint64 rdtsc() {
     unsigned long long int x;
     __asm__ volatile("rdtsc" : "=A"(x));
     return x;
   }
 
-  static constexpr td::uint64 rdtsc_frequency(void) {
+  static constexpr uint64 rdtsc_frequency() {
     return 2000'000'000;
   }
 
@@ -46,13 +48,13 @@ struct Clocks {
   static constexpr double inv_ticks_per_second() {
     return 0.5e-9;
   }
-#elif defined(__x86_64__)
-  static __inline__ td::uint64 rdtsc(void) {
+#elif defined(__x86_64__) or defined(__M_X64)
+  static uint64 rdtsc() {
     unsigned hi, lo;
     __asm__ __volatile__("rdtsc" : "=a"(lo), "=d"(hi));
     return ((unsigned long long)lo) | (((unsigned long long)hi) << 32);
   }
-  static constexpr td::uint64 rdtsc_frequency(void) {
+  static constexpr uint64 rdtsc_frequency() {
     return 2000'000'000;
   }
 
@@ -63,13 +65,13 @@ struct Clocks {
   static constexpr double inv_ticks_per_second() {
     return 0.5e-9;
   }
-#elif defined(__aarch64__)
-  static __inline__ td::uint64 rdtsc(void) {
+#elif defined(__aarch64__) or defined(_M_ARM64)
+  static uint64 rdtsc() {
     unsigned long long val;
     asm volatile("mrs %0, cntvct_el0" : "=r"(val));
     return val;
   }
-  static __inline__ td::uint64 rdtsc_frequency(void) {
+  static uint64 rdtsc_frequency() {
     unsigned long long val;
     asm volatile("mrs %0, cntfrq_el0" : "=r"(val));
     return val;
@@ -79,6 +81,21 @@ struct Clocks {
     return static_cast<double>(rdtsc_frequency());
   }
 
+  static double inv_ticks_per_second() {
+    return 1.0 / static_cast<double>(rdtsc_frequency());
+  }
+#else
+  static uint64 rdtsc() {
+    return monotonic_nano();
+  }
+  static uint64 rdtsc_frequency() {
+    return 1000'000'000;
+  }
+
+  static double ticks_per_second() {
+    return static_cast<double>(rdtsc_frequency());
+  }
+
   static double inv_ticks_per_second() {
     return 1.0 / static_cast<double>(rdtsc_frequency());
   }
diff --git a/validator/db/celldb.hpp b/validator/db/celldb.hpp
index f63d62cd..7cd36689 100644
--- a/validator/db/celldb.hpp
+++ b/validator/db/celldb.hpp
@@ -29,6 +29,8 @@
 #include "db-utils.h"
 #include "td/db/RocksDb.h"
 
+#include <optional>
+
 namespace rocksdb {
 class Statistics;
 class DB;