ProtocolBuffer object ByteSize is wrong - c++

Question

I have the following method:
void ConnectionManager::SendAll()
{
for (int t = 0; t < (int)m_Connections.size(); ++t)
{
if (m_Connections[t].socket != INVALID_SOCKET)
{
// Create the object
MessageID message;
message.set_type(MessageID::Type::MessageID_Type_PLAYERDATA);
for (int i = 0; i < (int)m_Connections.size(); ++i)
{
if (m_Connections[i].playerData.username() != google::protobuf::internal::kEmptyString)
{
auto temp = message.add_playerdata();
temp = &m_Connections[i].playerData;
}
}
if (message.playerdata_size() > 0)
{
// Serialize to byte array
int size = message.ByteSize();
void* buffer = malloc(size);
message.SerializeToArray(buffer, size);
Send(m_Connections[t].socket, buffer, size);
}
}
}
}
Now the problem lies at the end of this method, at the line:
int size = message.ByteSize();
I know that the data is loaded correctly (or it should be at least) but the size isn't right. It should be 30 and it returns 2. I have no idea what I'm doing wrong.
The data in m_Connections is available and should be reached by pointer temp. I think that, for some reason, the data is lost from the "message" object but I don't know how to solve it.

Answer 1

auto temp = message.add_playerdata();
temp = &m_Connections[i].playerData;
These lines look wrong. add_playerdata() returns a pointer. That means that the second line is just setting temp to some other pointer, not doing anything to the message which temp points at. It's more obvious if you write out the type rather than use auto:
MessageID::PlayerData* temp = message.add_playerdata();
temp = &m_Connections[i].playerData;
Maybe you wanted to do this instead:
*temp = m_Connections[i].playerData;
However, I do not see how this bug would lead to ByteSize() being 2. It looks like ByteSize() should only be 2 if you haven't added any players to the message, but then playerdata_size() would be zero, so you wouldn't get to the serialization step at all.