Get rid of static as a storage for the empty value

runtime-common/core/core-context.h

@@ -17,6 +17,7 @@ struct RuntimeContext final : vk::not_copyable {
   int32_t show_migration_php8_warning{};
   int32_t php_disable_warnings{};
   uint32_t empty_obj_count{};
+  void* empty_values{nullptr};
 
   string_buffer_lib_context sb_lib_context{};
   string_buffer static_SB{};

runtime-common/core/core-types/definition/mixed.inl

@@ -4,10 +4,17 @@
 
 #pragma once
 
+#include <cstddef>
+#include <typeindex>
+
 #include "common/algorithms/find.h"
 #include "common/smart_ptrs/intrusive_ptr.h"
 
+#include "runtime-common/core/allocator/script-allocator.h"
 #include "runtime-common/core/class-instance/refcountable-php-classes.h"
+#include "runtime-common/core/runtime-core.h"
+#include "runtime-common/core/std/containers.h"
+#include "runtime-common/core/utils/kphp-assert-core.h"
 #include "runtime-common/core/utils/migration-php8.h"
 
 #ifndef INCLUDED_FROM_KPHP_CORE
@@ -177,18 +184,30 @@ template<typename T>
 T& mixed::empty_value() noexcept {
   static_assert(vk::is_type_in_list<T, bool, int64_t, double, string, mixed, array<mixed>>{} || is_type_acceptable_for_mixed<T>::value, "unsupported type");
 
-  static T value;
-  value = T{};
-  return value;
+  auto& ctx{RuntimeContext::get()};
+
+  using type2value_t = kphp::stl::unordered_map<std::type_index, void*, kphp::memory::script_allocator>;
+  if (ctx.empty_values == nullptr) {
+    auto* raw_mem{RuntimeAllocator::get().alloc_script_memory(sizeof(type2value_t))};
+    php_assert(raw_mem);
+    ctx.empty_values = new (raw_mem) type2value_t{};
+    reinterpret_cast<type2value_t*>(ctx.empty_values)->reserve(6); // bool, int64_t, double, string, mixed, array<mixed>
+  }
+
+  auto* type2value{reinterpret_cast<type2value_t*>(ctx.empty_values)};
+  const auto it{type2value->find(std::type_index(typeid(T)))};
+  if (it != type2value->end()) {
+    *reinterpret_cast<T*>(it->second) = T{};
+    return *reinterpret_cast<T*>(it->second);
+  }
+
+  auto* raw_mem{RuntimeAllocator::get().alloc_script_memory(sizeof(T))};
+  php_assert(raw_mem);
+  return *reinterpret_cast<T*>(type2value->insert({std::type_index(typeid(T)), new (raw_mem) T{}}).first->second);
 }
 
 inline void mixed::reset_empty_values() noexcept {
-  empty_value<bool>();
-  empty_value<int64_t>();
-  empty_value<double>();
-  empty_value<string>();
-  empty_value<mixed>();
-  empty_value<array<mixed>>();
+  RuntimeContext::get().empty_values = nullptr;
 }
 
 template<class T>