Improvements to the refcount checker

I thought I was getting close so I spent a few days on this.
But there's still a lot of work left to be done to get it to be usable.

Makefile

@@ -922,7 +922,7 @@ watch_%:
 		TARGET=$(dir $@)$(patsubst watch_%,%,$(notdir $@)); \
 		clear; $(MAKE) $$TARGET $(WATCH_ARGS); true; \
 		while inotifywait -q -e modify -e attrib -e move -e move_self -e create -e delete -e delete_self \
-		Makefile $$(find src test \( -name '*.cpp' -o -name '*.h' -o -name '*.py' \) ); do clear; \
+		Makefile $$(find src test plugins \( -name '*.cpp' -o -name '*.h' -o -name '*.py' \) ); do clear; \
 			$(MAKE) $$TARGET $(WATCH_ARGS); \
 		done )
 		# Makefile $$(find \( -name '*.cpp' -o -name '*.h' -o -name '*.py' \) -o -type d ); do clear; $(MAKE) $(patsubst watch_%,%,$@); done )
@@ -1089,7 +1089,7 @@ refcheck_%: %.cpp refcount_checker
 	cd $(CMAKE_DIR_DBG); $(REFCOUNT_CHECKER_RUN_PATH) ../../$<
 .PHONY: dbg_refcheck_%
 dbg_refcheck_%: %.cpp refcount_checker
-	cd $(CMAKE_DIR_DBG); $(GDB) --args $(REFCOUNT_CHECKER_RUN_PATH) ../../$<
+	cd $(CMAKE_DIR_DBG); $(GDB) --ex run --ex "bt 20" --args $(REFCOUNT_CHECKER_RUN_PATH) ../../$<
 
 
 .PHONY: clang_lint

from_cpython/Include/pyerrors.h

@@ -90,7 +90,7 @@ typedef struct {
 PyAPI_FUNC(void) PyErr_SetNone(PyObject *) PYSTON_NOEXCEPT;
 PyAPI_FUNC(void) PyErr_SetObject(PyObject *, PyObject *) PYSTON_NOEXCEPT;
 PyAPI_FUNC(void) PyErr_SetString(PyObject *, const char *) PYSTON_NOEXCEPT;
-PyAPI_FUNC(PyObject *) PyErr_Occurred(void) PYSTON_NOEXCEPT;
+PyAPI_FUNC(BORROWED(PyObject *)) PyErr_Occurred(void) PYSTON_NOEXCEPT;
 PyAPI_FUNC(void) PyErr_Clear(void) PYSTON_NOEXCEPT;
 PyAPI_FUNC(void) PyErr_Fetch(PyObject **, PyObject **, PyObject **) PYSTON_NOEXCEPT;
 PyAPI_FUNC(void) PyErr_Restore(STOLEN(PyObject *), STOLEN(PyObject *), STOLEN(PyObject *)) PYSTON_NOEXCEPT;
@@ -219,7 +219,8 @@ PyAPI_FUNC(PyObject *) PyErr_SetFromErrnoWithUnicodeFilename(
     PyObject *, const Py_UNICODE *) PYSTON_NOEXCEPT;
 #endif /* MS_WINDOWS */
 
-PyAPI_FUNC(PyObject *) PyErr_Format(PyObject *, const char *, ...)
+// This actually always returns NULL:
+PyAPI_FUNC(BORROWED(PyObject *)) PyErr_Format(PyObject *, const char *, ...)
                         PYSTON_NOEXCEPT Py_GCC_ATTRIBUTE((format(printf, 2, 3)));
 
 #ifdef MS_WINDOWS

minibenchmarks/raytrace.py

@@ -65,9 +65,9 @@ VUP = Vector(0,1,0)
 VOUT = Vector(0,0,1)
 
 if not (VRIGHT.reflectThrough(VUP) == VRIGHT):
-    print 1/0
+    print(1/0)
 if not (Vector(-1,-1,0).reflectThrough(VUP) == Vector(-1,1,0)):
-    print 1/0
+    print(1/0)
 
 class Point(object):
     def __init__(self, initx, inity, initz):
@@ -216,7 +216,7 @@ class Scene(object):
         for y in range(canvas.height):
             currentfraction = 1.0 * y / canvas.height
             if currentfraction - previousfraction > 0.05:
-                print '%d%% complete' % int(currentfraction * 100)
+                print('%d%% complete' % int(currentfraction * 100))
                 previousfraction = currentfraction
             for x in range(canvas.width):
                 xcomp = vpRight.scale(x * pixelWidth - halfWidth)
@@ -225,7 +225,7 @@ class Scene(object):
                 colour = self.rayColour(ray)
                 canvas.plot(x,y,colour[0], colour[1], colour[2])
 
-        print 'Complete.'
+        print('Complete.')
         # canvas.save()
 
     def rayColour(self, ray):