fix serialization being different on mac

On Mac, size_t is a distinct type from uint64_t, and some
types (in wallet cache as well as cold/hot wallet transfer
data) use pairs/containers with size_t as fields. Mac would
save those as full size, while other platforms would save
them as varints. Might apply to other platforms where the
types are distinct.

There's a nasty hack for backward compatibility, which can
go after a couple forks.

1 files changed, 14 insertions, 9 deletions

diff --git a/src/serialization/container.h b/src/serialization/container.h
index d5e75bb4f..a4997c8ae 100644
--- a/src/serialization/container.h
+++ b/src/serialization/container.h
@@ -32,22 +32,27 @@ namespace serialization
 {
   namespace detail
   {
-    template <typename Archive, class T>
-    bool serialize_container_element(Archive& ar, T& e)
+    template<typename T>
+    inline constexpr bool use_container_varint() noexcept
     {
-      return ::do_serialize(ar, e);
+      return std::is_integral<T>::value && std::is_unsigned<T>::value && sizeof(T) > 1;
     }
 
-    template <typename Archive>
-    bool serialize_container_element(Archive& ar, uint32_t& e)
+    template <typename Archive, class T>
+    typename std::enable_if<!use_container_varint<T>(), bool>::type
+    serialize_container_element(Archive& ar, T& e)
     {
-      ar.serialize_varint(e);
-      return true;
+      return ::do_serialize(ar, e);
     }
 
-    template <typename Archive>
-    bool serialize_container_element(Archive& ar, uint64_t& e)
+    template<typename Archive, typename T>
+    typename std::enable_if<use_container_varint<T>(), bool>::type
+    serialize_container_element(Archive& ar, T& e)
     {
+      static constexpr const bool previously_varint = std::is_same<uint64_t, T>() || std::is_same<uint32_t, T>();
+
+      if (!previously_varint && ar.varint_bug_backward_compatibility_enabled() && !typename Archive::is_saving())
+        return ::do_serialize(ar, e);
       ar.serialize_varint(e);
       return true;
     }