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

bindings/pyroot/pythonizations/CMakeLists.txt

@@ -114,7 +114,6 @@ set(py_sources
 
 set(cpp_sources
     src/PyROOTModule.cxx
-    src/PyROOTWrapper.cxx
     src/RPyROOTApplication.cxx
     src/GenericPyz.cxx
     src/TClassPyz.cxx

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

@@ -185,15 +185,14 @@ 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()
+            facade.gROOT.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 = self.gROOT.FindObject(name)
             if res:
                 return res
         raise AttributeError("Failed to get attribute {} from ROOT".format(name))
@@ -204,7 +202,10 @@ 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()
+
+        # Make sure the interpreter is initialized once gROOT has been initialized
+        cppyy.gbl.TInterpreter.Instance()
 
         # Setup interactive usage from Python
         self.__dict__["app"] = PyROOTApplication(self.PyConfig, self._is_ipython)
@@ -387,7 +388,7 @@ def TMVA(self):
         from ._pythonization import _tmva
 
         ns = self._fallback_getattr("TMVA")
-        hasRDF = "dataframe" in gROOT.GetConfigFeatures()
+        hasRDF = "dataframe" in self.gROOT.GetConfigFeatures()
         if hasRDF:
             try:
                 from ._pythonization._tmva import inject_rbatchgenerator, _AsRTensor, SaveXGBoost

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

@@ -16,8 +16,6 @@
 
 from .. import pythonization
 
-from libROOTPythonizations import gROOT
-
 from ._factory import Factory
 from ._dataloader import DataLoader
 from ._crossvalidation import CrossValidation
@@ -45,7 +43,7 @@ def inject_rbatchgenerator(ns):
 
 from ._gnn import RModel_GNN, RModel_GraphIndependent
 
-hasRDF = "dataframe" in gROOT.GetConfigFeatures()
+hasRDF = "dataframe" in cppyy.gbl.ROOT.GetROOT().GetConfigFeatures()
 if hasRDF:
     from ._rtensor import get_array_interface, add_array_interface_property, RTensorGetitem, pythonize_rtensor, _AsRTensor
 

bindings/pyroot/pythonizations/src/PyROOTModule.cxx

@@ -11,15 +11,16 @@
 
 // Bindings
 #include "PyROOTPythonize.h"
-#include "PyROOTWrapper.h"
 #include "RPyROOTApplication.h"
+#include "TMemoryRegulator.h"
 
 // Cppyy
 #include "CPyCppyy/API.h"
 #include "../../cppyy/CPyCppyy/src/CallContext.h"
 #include "../../cppyy/CPyCppyy/src/ProxyWrappers.h"
 
 // ROOT
+#include "TInterpreter.h"
 #include "TROOT.h"
 #include "TSystem.h"
 #include "RConfigure.h"
@@ -62,6 +63,20 @@ PyObject *RegisterExecutorAlias(PyObject * /*self*/, PyObject *args)
 
 } // namespace PyROOT
 
+namespace {
+
+PyROOT::RegulatorCleanup &GetRegulatorCleanup()
+{
+   // The object is thread-local because it can happen that we call into
+   // C++ code (from the PyROOT CPython extension, from CPyCppyy or from cling)
+   // from different Python threads. A notable example is within a distributed
+   // RDataFrame application running on Dask.
+   thread_local PyROOT::RegulatorCleanup m;
+   return m;
+}
+
+} // namespace
+
 // Methods offered by the interface
 static PyMethodDef gPyROOTMethods[] = {
    {(char *)"AddCPPInstancePickling", (PyCFunction)PyROOT::AddCPPInstancePickling, METH_VARARGS,
@@ -144,8 +159,16 @@ extern "C" PyObject *PyInit_libROOTPythonizations()
    // keep gRootModule, but do not increase its reference count even as it is borrowed,
    // or a self-referencing cycle would be created
 
-   // setup PyROOT
-   PyROOT::Init();
+   // Initialize and acquire the GIL to allow for threading in ROOT
+#if PY_VERSION_HEX < 0x03090000
+   PyEval_InitThreads();
+#endif
+
+   // Memory management
+   gROOT->GetListOfCleanups()->Add(&GetRegulatorCleanup());
+
+   // Make sure the interpreter is initialized once gROOT has been initialized
+   TInterpreter::Instance();
 
    // signal policy: don't abort interpreter in interactive mode
    CallContext::SetGlobalSignalPolicy(!gROOT->IsBatch());

bindings/pyroot/pythonizations/test/numbadeclare.py

@@ -77,7 +77,7 @@ def fn1(x):
 
         self.assertTrue(hasattr(fn1, "__cpp_wrapper__"))
         self.assertTrue(type(fn1.__cpp_wrapper__) == str)
-        self.assertEqual(sys.getrefcount(fn1.__cpp_wrapper__), 3)
+        self.assertLessEqual(sys.getrefcount(fn1.__cpp_wrapper__), 3)
 
         self.assertTrue(hasattr(fn1, "__py_wrapper__"))
         self.assertTrue(type(fn1.__py_wrapper__) == str)