[PyROOT] Retain C++ ownership for TF2, TF3

Fixes root-project#16942

bindings/pyroot/pythonizations/CMakeLists.txt

@@ -97,6 +97,8 @@ set(py_sources
   ROOT/_pythonization/_tdirectory.py
   ROOT/_pythonization/_tdirectoryfile.py
   ROOT/_pythonization/_tf1.py
+  ROOT/_pythonization/_tf2.py
+  ROOT/_pythonization/_tf3.py
   ROOT/_pythonization/_tfile.py
   ROOT/_pythonization/_tformula.py
   ROOT/_pythonization/_tgraph.py

bindings/pyroot/pythonizations/python/ROOT/_pythonization/_tf2.py

@@ -0,0 +1,25 @@
+# Author: Vincenzo Eduardo Padulano CERN 11/2024
+
+################################################################################
+# Copyright (C) 1995-2024, Rene Brun and Fons Rademakers.                      #
+# All rights reserved.                                                         #
+#                                                                              #
+# For the licensing terms see $ROOTSYS/LICENSE.                                #
+# For the list of contributors see $ROOTSYS/README/CREDITS.                    #
+################################################################################
+from . import pythonization
+
+def _TF2_constructor(self, *args, **kwargs):
+    """
+    Forward the arguments to the C++ constructor and retain ownership. This
+    helps avoiding double deletes due to ROOT automatic memory management.
+    """
+    self._cpp_constructor(*args, **kwargs)
+    import ROOT
+    ROOT.SetOwnership(self, False)
+
+
+@pythonization("TF2")
+def pythonize_tf1(klass):
+    klass._cpp_constructor = klass.__init__
+    klass.__init__ = _TF2_constructor

bindings/pyroot/pythonizations/python/ROOT/_pythonization/_tf3.py

@@ -0,0 +1,25 @@
+# Author: Vincenzo Eduardo Padulano CERN 11/2024
+
+################################################################################
+# Copyright (C) 1995-2024, Rene Brun and Fons Rademakers.                      #
+# All rights reserved.                                                         #
+#                                                                              #
+# For the licensing terms see $ROOTSYS/LICENSE.                                #
+# For the list of contributors see $ROOTSYS/README/CREDITS.                    #
+################################################################################
+from . import pythonization
+
+def _TF3_constructor(self, *args, **kwargs):
+    """
+    Forward the arguments to the C++ constructor and retain ownership. This
+    helps avoiding double deletes due to ROOT automatic memory management.
+    """
+    self._cpp_constructor(*args, **kwargs)
+    import ROOT
+    ROOT.SetOwnership(self, False)
+
+
+@pythonization("TF3")
+def pythonize_tf1(klass):
+    klass._cpp_constructor = klass.__init__
+    klass.__init__ = _TF3_constructor

bindings/pyroot/pythonizations/test/memory.py

@@ -53,5 +53,18 @@ def test_tstyle_memory_management(self):
         groot.SetStyle(style.GetName())
         groot.ForceStyle()
 
+    def test_tf2_memory_regulation(self):
+        """Regression test for https://github.com/root-project/root/issues/16942"""
+        # The test is just that the memory regulation works correctly and the
+        # application does not segfault
+        f2 = ROOT.TF2("f2", "sin(x)*sin(y)/x/y")
+
+
+    def test_tf3_memory_regulation(self):
+        """Make sure TF3 is properly managed by the memory regulation logic"""
+        # The test is just that the memory regulation works correctly and the
+        # application does not segfault
+        f3 = ROOT.TF3("f3","[0] * sin(x) + [1] * cos(y) + [2] * z",0,10,0,10,0,10)
+
 if __name__ == '__main__':
     unittest.main()