[RF][PyROOT] Fix memory leaks with RooFit command arguments in PyROOT

bindings/pyroot/pythonizations/CMakeLists.txt

@@ -43,6 +43,7 @@ if(roofit)
         ROOT/_pythonization/_roofit/_roogenfitstudy.py
         ROOT/_pythonization/_roofit/_rooglobalfunc.py
         ROOT/_pythonization/_roofit/_roojsonfactorywstool.py
+        ROOT/_pythonization/_roofit/_roolinkedlist.py
         ROOT/_pythonization/_roofit/_roomcstudy.py
         ROOT/_pythonization/_roofit/_roomsgservice.py
         ROOT/_pythonization/_roofit/_roonllvar.py

bindings/pyroot/pythonizations/python/ROOT/_pythonization/_roofit/__init__.py

@@ -48,6 +48,7 @@
     MarkerStyle,
 )
 from ._roojsonfactorywstool import RooJSONFactoryWSTool
+from ._roolinkedlist import RooLinkedList
 from ._roomcstudy import RooMCStudy
 from ._roomsgservice import RooMsgService
 from ._roonllvar import RooNLLVar
@@ -79,6 +80,7 @@
     RooDecay,
     RooGenFitStudy,
     RooJSONFactoryWSTool,
+    RooLinkedList,
     RooMCStudy,
     RooMsgService,
     RooNLLVar,

bindings/pyroot/pythonizations/python/ROOT/_pythonization/_roofit/_roolinkedlist.py

@@ -0,0 +1,30 @@
+# Authors:
+# * Jonas Rembser 09/2023
+
+################################################################################
+# Copyright (C) 1995-2020, Rene Brun and Fons Rademakers.                      #
+# All rights reserved.                                                         #
+#                                                                              #
+# For the licensing terms see $ROOTSYS/LICENSE.                                #
+# For the list of contributors see $ROOTSYS/README/CREDITS.                    #
+################################################################################
+
+
+class RooLinkedList(object):
+
+    def Add(self, arg):
+        # The Add() method is only changed for the sake of changing the memory
+        # policy of the cppyy overload. The signature of the original C++
+        # function is RooLinkedList::Add(RooAbsArg *arg). PyROOT is wrongly
+        # interpreting this as the RooLinkedList taking ownership of the
+        # RooAbsArg. This results in a memory leak because nobody feels
+        # responsible for deleting the arg. This can be fixed by setting the
+        # memory policy of the method to "strict" and not to "heuristic".
+        #
+        # This might become unnecessary in the future if it is decided to set
+        # the global memory policy to "strict" in _facade.py.
+
+        import ROOT
+
+        self._Add.__mempolicy__ = ROOT.kMemoryStrict
+        return self._Add(arg)