partial bitcoin#24169: Add --enable-c++20 option

includes:
- fae679065e4ef0c6383bbdd1876aaed6c1e40104

src/net.h

@@ -133,15 +133,22 @@ struct AddedNodeInfo
 class CNodeStats;
 class CClientUIInterface;
 
-struct CSerializedNetMsg
+struct CSerializedNetMsg {
-{
     CSerializedNetMsg() = default;
     CSerializedNetMsg(CSerializedNetMsg&&) = default;
     CSerializedNetMsg& operator=(CSerializedNetMsg&&) = default;
-    // No copying, only moves.
+    // No implicit copying, only moves.
     CSerializedNetMsg(const CSerializedNetMsg& msg) = delete;
     CSerializedNetMsg& operator=(const CSerializedNetMsg&) = delete;
 
+    CSerializedNetMsg Copy() const
+    {
+        CSerializedNetMsg copy;
+        copy.data = data;
+        copy.m_type = m_type;
+        return copy;
+    }
+
     std::vector<unsigned char> data;
     std::string m_type;
 };

src/net_processing.cpp

@@ -2067,7 +2067,7 @@ void PeerManagerImpl::NewPoWValidBlock(const CBlockIndex *pindex, const std::sha
                     hashBlock.ToString(), pnode->GetId());
 
             const CSerializedNetMsg& ser_cmpctblock{lazy_ser.get()};
-            m_connman.PushMessage(pnode, CSerializedNetMsg{ser_cmpctblock.data, ser_cmpctblock.m_type});
+            m_connman.PushMessage(pnode, ser_cmpctblock.Copy());
             state.pindexBestHeaderSent = pindex;
         }
     });