fix for [#17878] Scripts operating on blender objects don't clear memory after a crash

This is an interesting bug since it is likely the cause of many other suspicious python crashes in blender.

sys.last_traceback would store references to PyObjects at the point of the crash.
it would only free these when sys.last_traceback was set again or on exit.

This caused many crashes in the BGE while testing since python would end up freeing invalid game objects -
When running scripts with errors, Blender would crash every 2-5 runs - in my test just now it crashed after 4 trys.

It could also segfault blender, when (for eg) you run a script that has objects referenced. then load a new file and run another script that raises an error.
In this case all the invalid Blender-Object's user counts would be decremented, even though none of the pointers were still valid.

1 files changed, 14 insertions, 0 deletions

diff --git a/source/gameengine/GameLogic/SCA_PythonController.cpp b/source/gameengine/GameLogic/SCA_PythonController.cpp
index 4cb9bc8fe53..1bbb93e0acc 100644
--- a/source/gameengine/GameLogic/SCA_PythonController.cpp
+++ b/source/gameengine/GameLogic/SCA_PythonController.cpp
@@ -262,6 +262,13 @@ void SCA_PythonController::Trigger(SCA_LogicManager* logicmgr)
 			printf("Python compile error from controller \"%s\": \n", GetName().Ptr());
 			//PyRun_SimpleString(m_scriptText.Ptr());
 			PyErr_Print();
+			
+			/* Added in 2.48a, the last_traceback can reference Objects for example, increasing
+			 * their user count. Not to mention holding references to wrapped data.
+			 * This is especially bad when the PyObject for the wrapped data is free'd, after blender 
+			 * has alredy dealocated the pointer */
+			PySys_SetObject( "last_traceback", Py_None);
+			
 			return;
 		}
 		m_bModified=false;
@@ -298,6 +305,13 @@ void SCA_PythonController::Trigger(SCA_LogicManager* logicmgr)
 		// something is wrong, tell the user what went wrong
 		printf("Python script error from controller \"%s\": \n", GetName().Ptr());
 		PyErr_Print();
+		
+		/* Added in 2.48a, the last_traceback can reference Objects for example, increasing
+		 * their user count. Not to mention holding references to wrapped data.
+		 * This is especially bad when the PyObject for the wrapped data is free'd, after blender 
+		 * has alredy dealocated the pointer */
+		PySys_SetObject( "last_traceback", Py_None);
+		
 		//PyRun_SimpleString(m_scriptText.Ptr());
 	}