Downgrade for old compiler

CMakeLists.txt

@@ -3,6 +3,7 @@ set(headers
     src/espcrc32builder.h
     src/esprandom.h
     src/espstrutils.h
+    src/futurecpp.h
     src/lockhelper.h
     src/lockingqueue.h
     src/recursivelockhelper.h

src/espstrutils.cpp

@@ -10,6 +10,7 @@
 #include <esp_log.h>
 
 // 3rdparty lib includes
+#include <futurecpp.h>
 #include <fmt/core.h>
 
 using namespace std::string_literals;

src/futurecpp.h

@@ -0,0 +1,30 @@
+#pragma once
+
+// system includes
+#include <cstring>
+#include <limits>
+#include <type_traits>
+
+// C++20 backports (until espressif finally updates their aged compiler suite)
+
+namespace std {
+template <class To, class From>
+typename std::enable_if_t<
+    sizeof(To) == sizeof(From) && std::is_trivially_copyable_v<From> && std::is_trivially_copyable_v<To>,
+    To>
+// constexpr support needs compiler magic
+bit_cast(const From& src) noexcept
+{
+    static_assert(std::is_trivially_constructible_v<To>,
+                  "This implementation additionally requires destination type to be trivially constructible");
+
+    To dst;
+    std::memcpy(&dst, &src, sizeof(To));
+    return dst;
+}
+
+template <typename EnumT, typename = std::enable_if_t<std::is_enum<EnumT>{}>>
+constexpr std::underlying_type_t<EnumT> to_underlying(EnumT e) noexcept {
+    return static_cast<std::underlying_type_t<EnumT>>(e);
+}
+} // namespace std

src/taskutils.cpp

@@ -9,6 +9,9 @@
 // esp-idf includes
 #include <esp_log.h>
 
+// 3rdparty lib includes
+#include <futurecpp.h>
+
 namespace espcpputils {
 namespace {
 constexpr const char * const TAG = "ESPCPPUTILS";

src/wrappers/websocket_client.h

@@ -11,6 +11,7 @@
 
 // 3rdparty lib includes
 #include <fmt/core.h>
+#include <futurecpp.h>
 
 namespace espcpputils {
 class websocket_client