[PyROOT] Expose gROOT via CPython extension for use in atexit handler

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

@@ -185,14 +185,15 @@ 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.
-            facade.gROOT.EndOfProcessCleanups()
+            backend.gROOT.EndOfProcessCleanups()
 
 
 atexit.register(cleanup)

bindings/pyroot/pythonizations/src/PyROOTModule.cxx

@@ -20,6 +20,7 @@
 #include "../../cppyy/CPyCppyy/src/ProxyWrappers.h"
 
 // ROOT
+#include "TInterpreter.h"
 #include "TROOT.h"
 #include "TSystem.h"
 #include "RConfigure.h"
@@ -166,6 +167,12 @@ extern "C" PyObject *PyInit_libROOTPythonizations()
    // Memory management
    gROOT->GetListOfCleanups()->Add(&GetRegulatorCleanup());
 
+   // Bind ROOT globals that will be needed in ROOT.py
+   PyModule_AddObject(gRootModule, "gROOT", CPyCppyy::Instance_FromVoidPtr(gROOT, "TROOT"));
+
+   // Make sure interpreter is initialized now
+   TInterpreter::Instance();
+
    // signal policy: don't abort interpreter in interactive mode
    CallContext::SetGlobalSignalPolicy(!gROOT->IsBatch());