Fix some issues that occur when compiling with c++17 or c++20 (#149)

- The `noexcept` specifier on an std::function will not compile in c++17
or c++20
- In c++20 is_pod is deprecated
- In c++20 the separate functions for atomic shared pointers are
deprecated

src/dsl/word/UDP.hpp

@@ -132,7 +132,7 @@ namespace dsl {
                 // We can cast ourselves to a reference type so long as
                 // that reference type is plain old data
                 template <typename T>
-                operator std::enable_if_t<std::is_pod<T>::value, const T&>() {
+                operator std::enable_if_t<std::is_trivially_copyable<T>::value, const T&>() {
                     return *reinterpret_cast<const T*>(payload.data());
                 }
             };

src/threading/ReactionTask.hpp

@@ -57,7 +57,7 @@ namespace threading {
 
     public:
         /// Type of the functions that ReactionTasks execute
-        using TaskFunction = std::function<void(ReactionTask&) noexcept>;
+        using TaskFunction = std::function<void(ReactionTask&)>;
 
         /**
          * Gets the current executing task, or nullptr if there isn't one.

src/util/TypeMap.hpp

@@ -58,8 +58,12 @@ namespace util {
         TypeMap operator=(TypeMap&& /*other*/) noexcept = delete;
 
     private:
-        /// The data variable where the data is stored for this map key.
+/// The data variable where the data is stored for this map key.
+#if __cplusplus >= 202002L
+        static std::atomic<std::shared_ptr<Value>> data;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
+#else
         static std::shared_ptr<Value> data;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
+#endif
 
     public:
         /**
@@ -68,7 +72,11 @@ namespace util {
          * @param d A pointer to the data to be stored (the map takes ownership)
          */
         static void set(std::shared_ptr<Value> d) {
+#if __cplusplus >= 202002L
+            data.store(std::move(d), std::memory_order_release);
+#else
             std::atomic_store_explicit(&data, std::move(d), std::memory_order_release);
+#endif
         }
 
         /**
@@ -77,14 +85,23 @@ namespace util {
          * @return A shared_ptr to the data that was previously stored
          */
         static std::shared_ptr<Value> get() {
+#if __cplusplus >= 202002L
+            return data.load(std::memory_order_acquire);
+#else
             return std::atomic_load_explicit(&data, std::memory_order_acquire);
+#endif
         }
     };
 
     /// Initialize our shared_ptr data
     template <typename MapID, typename Key, typename Value>
-    std::shared_ptr<Value>
-        TypeMap<MapID, Key, Value>::data;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
+#if __cplusplus >= 202002L
+    // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+    std::atomic<std::shared_ptr<Value>> TypeMap<MapID, Key, Value>::data;
+#else
+    // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
+    std::shared_ptr<Value> TypeMap<MapID, Key, Value>::data;
+#endif
 
 }  // namespace util
 }  // namespace NUClear