Solve #16375

TestData.cxx

@@ -1,6 +1,8 @@
 #include "TestData.h"
 #include "a_member.h"
 
+#include <TBuffer.h>
+
 ClassImp(TestData);
 
 TestData::~TestData() { delete sm; }
@@ -12,3 +14,25 @@ TestData::TestData() { Init(); }
 TestData::TestData(const TestData &other) = default;
 
 double TestData::Mag() const { return sm->get().Mag(); }
+
+//______________________________________________________________________________
+void TestData::Streamer(TBuffer &R__b)
+{
+   // Stream an object of class TestData.
+
+   if (R__b.IsReading()) {
+      UInt_t R__s, R__c;
+      Version_t R__v = R__b.ReadVersion(&R__s, &R__c);
+      if (R__v < 2) {
+         TObject::Streamer(R__b);
+         delete sm;
+         sm = nullptr;
+         R__b >> sm;
+         R__b.CheckByteCount(R__s, R__c, TestData::IsA());
+      } else {
+         R__b.ReadClassBuffer(TestData::Class(),this);
+      }
+   } else {
+      R__b.WriteClassBuffer(TestData::Class(),this);
+   }
+}

TestData.h

@@ -19,5 +19,5 @@ class TestData : public TObject {
   void Init();
   a_member *sm;
 
-  ClassDef(TestData, 1)
+  ClassDefOverride(TestData, 2)
 };

TestDataLinkDef.h

@@ -6,7 +6,7 @@
 
 // the missing "+" in TestData is 
 // the key to the problem
-#pragma link C++ class TestData;
+#pragma link C++ class TestData-;
 #pragma link C++ class a_member+;
 
 #endif

a_member.h

@@ -12,5 +12,5 @@ class a_member : public TObject {
   [[nodiscard]] const TLorentzVector& get() const;
 
 private:
-  ClassDef(a_member, 1)
-};
+  ClassDefOverride(a_member, 1)
+};

read_old.cxx

@@ -11,5 +11,6 @@ int main() {
     tree->GetEntry(i);
   }
   file.Close();
+  delete data;
   return 0;
-}
+}