[PyROOT] Don't add gROOT and other globals manually to PyROOT via C++

This is not necessary if we consider that `gROOT` is actually a
preprocessor macro that aliases to `ROOT::GetROOT()`, which we can use
directly in Python via cppyy. Same with the `gInterpreter`.

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

@@ -176,6 +176,8 @@ def find_spec(self, fullname: str, path, target=None) -> ModuleSpec:
 # Register cleanup
 import atexit
 
+# Private handle to gROOT for later cleanup
+_gROOTForCleanup = cppyy.gbl.ROOT.GetROOT()
 
 def cleanup():
     # If spawned, stop thread which processes ROOT events
@@ -185,15 +187,14 @@ def cleanup():
         facade.__dict__["app"].process_root_events.join()
 
     if "libROOTPythonizations" in sys.modules:
-        backend = sys.modules["libROOTPythonizations"]
 
         from ROOT import PyConfig
 
         if PyConfig.ShutDown:
             # Hard teardown: run part of the gROOT shutdown sequence.
             # Running it here ensures that it is done before any ROOT libraries
             # are off-loaded, with unspecified order of static object destruction.
-            backend.gROOT.EndOfProcessCleanups()
+            _gROOTForCleanup.EndOfProcessCleanups()
 
 
 atexit.register(cleanup)

bindings/pyroot/pythonizations/python/ROOT/_facade.py

@@ -8,8 +8,6 @@
 
 import cppyy.ll
 
-from libROOTPythonizations import gROOT
-
 from ._application import PyROOTApplication
 from ._numbadeclare import _NumbaDeclareDecorator
 
@@ -36,7 +34,7 @@ class _gROOTWrapper(object):
 
     def __init__(self, facade):
         self.__dict__["_facade"] = facade
-        self.__dict__["_gROOT"] = gROOT
+        self.__dict__["_gROOT"] = cppyy.gbl.ROOT.GetROOT()
 
     def __getattr__(self, name):
         if name != "SetBatch" and self._facade.__dict__["gROOT"] != self._gROOT:
@@ -158,7 +156,7 @@ def _fallback_getattr(self, name):
         elif hasattr(cppyy.gbl.ROOT, name):
             return getattr(cppyy.gbl.ROOT, name)
         else:
-            res = gROOT.FindObject(name)
+            res = cppyy.gbl.ROOT.GetROOT().FindObject(name)
             if res:
                 return res
         raise AttributeError("Failed to get attribute {} from ROOT".format(name))
@@ -204,7 +202,7 @@ def _register_converters_and_executors(self):
 
     def _finalSetup(self):
         # Prevent this method from being re-entered through the gROOT wrapper
-        self.__dict__["gROOT"] = gROOT
+        self.__dict__["gROOT"] = cppyy.gbl.ROOT.GetROOT()
 
         # Setup interactive usage from Python
         self.__dict__["app"] = PyROOTApplication(self.PyConfig, self._is_ipython)

bindings/pyroot/pythonizations/src/PyROOTWrapper.cxx

@@ -13,33 +13,13 @@
 #include "PyROOTWrapper.h"
 #include "TMemoryRegulator.h"
 
-// Cppyy
-#include "CPyCppyy/API.h"
-
 // ROOT
 #include "TROOT.h"
-#include "TSystem.h"
-#include "TClass.h"
-#include "TInterpreter.h"
-#include "DllImport.h"
 
 namespace PyROOT {
 R__EXTERN PyObject *gRootModule;
 }
 
-using namespace PyROOT;
-
-namespace {
-
-static void AddToGlobalScope(const char *label, TObject *obj, const char *classname)
-{
-   // Bind the given object with the given class in the global scope with the
-   // given label for its reference.
-   PyModule_AddObject(gRootModule, label, CPyCppyy::Instance_FromVoidPtr(obj, classname));
-}
-
-} // unnamed namespace
-
 PyROOT::RegulatorCleanup &GetRegulatorCleanup()
 {
    // The object is thread-local because it can happen that we call into
@@ -59,9 +39,4 @@ void PyROOT::Init()
 
    // Memory management
    gROOT->GetListOfCleanups()->Add(&GetRegulatorCleanup());
-
-   // Bind ROOT globals that will be needed in ROOT.py
-   AddToGlobalScope("gROOT", gROOT, gROOT->IsA()->GetName());
-   AddToGlobalScope("gSystem", gSystem, gSystem->IsA()->GetName());
-   AddToGlobalScope("gInterpreter", gInterpreter, gInterpreter->IsA()->GetName());
 }