Use Py_VISIT in all tp_traverse methods, instead of traversing manually or

using a custom, nearly-identical macro. This probably changes how some of
these functions are compiled, which may result in fractionally slower (or
faster) execution. Considering the nature of traversal, visiting much of the
address space in unpredictable patterns, I'd argue the code readability and
maintainability is well worth it ;P

13 files changed, 68 insertions, 257 deletions

diff --git a/Objects/cellobject.c b/Objects/cellobject.c
index e617e5e5f3..da48dea745 100644
--- a/Objects/cellobject.c
+++ b/Objects/cellobject.c
@@ -73,8 +73,7 @@ cell_repr(PyCellObject *op)
 static int
 cell_traverse(PyCellObject *op, visitproc visit, void *arg)
 {
-	if (op->ob_ref)
-		return visit(op->ob_ref, arg);
+	Py_VISIT(op->ob_ref);
 	return 0;
 }
 
diff --git a/Objects/classobject.c b/Objects/classobject.c
index 474c666c28..a723bd6012 100644
--- a/Objects/classobject.c
+++ b/Objects/classobject.c
@@ -404,37 +404,12 @@ class_str(PyClassObject *op)
 static int
 class_traverse(PyClassObject *o, visitproc visit, void *arg)
 {
-	int err;
-	if (o->cl_bases) {
-		err = visit(o->cl_bases, arg);
-		if (err)
-			return err;
-	}
-	if (o->cl_dict) {
-		err = visit(o->cl_dict, arg);
-		if (err)
-			return err;
-	}
-	if (o->cl_name) {
-		err = visit(o->cl_name, arg);
-		if (err)
-			return err;
-	}
-	if (o->cl_getattr) {
-		err = visit(o->cl_getattr, arg);
-		if (err)
-			return err;
-	}
-	if (o->cl_setattr) {
-		err = visit(o->cl_setattr, arg);
-		if (err)
-			return err;
-	}
-	if (o->cl_delattr) {
-		err = visit(o->cl_delattr, arg);
-		if (err)
-			return err;
-	}
+	Py_VISIT(o->cl_bases);
+	Py_VISIT(o->cl_dict);
+	Py_VISIT(o->cl_name);
+	Py_VISIT(o->cl_getattr);
+	Py_VISIT(o->cl_setattr);
+	Py_VISIT(o->cl_delattr);
 	return 0;
 }
 
@@ -979,17 +954,8 @@ instance_hash(PyInstanceObject *inst)
 static int
 instance_traverse(PyInstanceObject *o, visitproc visit, void *arg)
 {
-	int err;
-	if (o->in_class) {
-		err = visit((PyObject *)(o->in_class), arg);
-		if (err)
-			return err;
-	}
-	if (o->in_dict) {
-		err = visit(o->in_dict, arg);
-		if (err)
-			return err;
-	}
+	Py_VISIT(o->in_class);
+	Py_VISIT(o->in_dict);
 	return 0;
 }
 
@@ -2348,22 +2314,9 @@ instancemethod_hash(PyMethodObject *a)
 static int
 instancemethod_traverse(PyMethodObject *im, visitproc visit, void *arg)
 {
-	int err;
-	if (im->im_func) {
-		err = visit(im->im_func, arg);
-		if (err)
-			return err;
-	}
-	if (im->im_self) {
-		err = visit(im->im_self, arg);
-		if (err)
-			return err;
-	}
-	if (im->im_class) {
-		err = visit(im->im_class, arg);
-		if (err)
-			return err;
-	}
+	Py_VISIT(im->im_func);
+	Py_VISIT(im->im_self);
+	Py_VISIT(im->im_class);
 	return 0;
 }
 
diff --git a/Objects/descrobject.c b/Objects/descrobject.c
index bfa25e98f6..561ba4a5f0 100644
--- a/Objects/descrobject.c
+++ b/Objects/descrobject.c
@@ -377,13 +377,7 @@ static int
 descr_traverse(PyObject *self, visitproc visit, void *arg)
 {
 	PyDescrObject *descr = (PyDescrObject *)self;
-	int err;
-
-	if (descr->d_type) {
-		err = visit((PyObject *)(descr->d_type), arg);
-		if (err)
-			return err;
-	}
+	Py_VISIT(descr->d_type);
 	return 0;
 }
 
@@ -814,13 +808,7 @@ static int
 proxy_traverse(PyObject *self, visitproc visit, void *arg)
 {
 	proxyobject *pp = (proxyobject *)self;
-	int err;
-
-	if (pp->dict) {
-		err = visit(pp->dict, arg);
-		if (err)
-			return err;
-	}
+	Py_VISIT(pp->dict);
 	return 0;
 }
 
@@ -999,18 +987,8 @@ static int
 wrapper_traverse(PyObject *self, visitproc visit, void *arg)
 {
 	wrapperobject *wp = (wrapperobject *)self;
-	int err;
-
-	if (wp->descr) {
-		err = visit((PyObject *)(wp->descr), arg);
-		if (err)
-			return err;
-	}
-	if (wp->self) {
-		err = visit(wp->self, arg);
-		if (err)
-			return err;
-	}
+	Py_VISIT(wp->descr);
+	Py_VISIT(wp->self);
 	return 0;
 }
 
@@ -1237,20 +1215,10 @@ static int
 property_traverse(PyObject *self, visitproc visit, void *arg)
 {
 	propertyobject *pp = (propertyobject *)self;
-	int err;
-
-#define VISIT(SLOT) \
-	if (pp->SLOT) { \
-		err = visit((PyObject *)(pp->SLOT), arg); \
-		if (err) \
-			return err; \
-	}
-
-	VISIT(prop_get);
-	VISIT(prop_set);
-	VISIT(prop_del);
-	VISIT(prop_doc);
-
+	Py_VISIT(pp->prop_get);
+	Py_VISIT(pp->prop_set);
+	Py_VISIT(pp->prop_del);
+	Py_VISIT(pp->prop_doc);
 	return 0;
 }
 
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 31ef958e63..f5799ee09f 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -1732,17 +1732,12 @@ static int
 dict_traverse(PyObject *op, visitproc visit, void *arg)
 {
 	Py_ssize_t i = 0;
-	int err;
 	PyObject *pk;
 	PyObject *pv;
 
 	while (PyDict_Next(op, &i, &pk, &pv)) {
-		err = visit(pk, arg);
-		if (err)
-			return err;
-		err = visit(pv, arg);
-		if (err)
-			return err;
+		Py_VISIT(pk);
+		Py_VISIT(pv);
 	}
 	return 0;
 }
diff --git a/Objects/enumobject.c b/Objects/enumobject.c
index cd31dc15d5..a8f43e0738 100644
--- a/Objects/enumobject.c
+++ b/Objects/enumobject.c
@@ -49,18 +49,8 @@ enum_dealloc(enumobject *en)
 static int
 enum_traverse(enumobject *en, visitproc visit, void *arg)
 {
-	int err;
-
-	if (en->en_sit) {
-		err = visit(en->en_sit, arg);
-		if (err)
-			return err;
-	}
-	if (en->en_result) {
-		err = visit(en->en_result, arg);
-		if (err)
-			return err;
-	}
+	Py_VISIT(en->en_sit);
+	Py_VISIT(en->en_result);
 	return 0;
 }
 
@@ -205,8 +195,7 @@ reversed_dealloc(reversedobject *ro)
 static int
 reversed_traverse(reversedobject *ro, visitproc visit, void *arg)
 {
-	if (ro->seq)
-		return visit((PyObject *)(ro->seq), arg);
+	Py_VISIT(ro->seq);
 	return 0;
 }
 
diff --git a/Objects/funcobject.c b/Objects/funcobject.c
index b86319cad8..59cb519507 100644
--- a/Objects/funcobject.c
+++ b/Objects/funcobject.c
@@ -466,47 +466,14 @@ func_repr(PyFunctionObject *op)
 static int
 func_traverse(PyFunctionObject *f, visitproc visit, void *arg)
 {
-	int err;
-	if (f->func_code) {
-		err = visit(f->func_code, arg);
-		if (err)
-			return err;
-	}
-	if (f->func_globals) {
-		err = visit(f->func_globals, arg);
-		if (err)
-			return err;
-	}
-	if (f->func_module) {
-		err = visit(f->func_module, arg);
-		if (err)
-			return err;
-	}
-	if (f->func_defaults) {
-		err = visit(f->func_defaults, arg);
-		if (err)
-			return err;
-	}
-	if (f->func_doc) {
-		err = visit(f->func_doc, arg);
-		if (err)
-			return err;
-	}
-	if (f->func_name) {
-		err = visit(f->func_name, arg);
-		if (err)
-			return err;
-	}
-	if (f->func_dict) {
-		err = visit(f->func_dict, arg);
-		if (err)
-			return err;
-	}
-	if (f->func_closure) {
-		err = visit(f->func_closure, arg);
-		if (err)
-			return err;
-	}
+	Py_VISIT(f->func_code);
+	Py_VISIT(f->func_globals);
+	Py_VISIT(f->func_module);
+	Py_VISIT(f->func_defaults);
+	Py_VISIT(f->func_doc);
+	Py_VISIT(f->func_name);
+	Py_VISIT(f->func_dict);
+	Py_VISIT(f->func_closure);
 	return 0;
 }
 
@@ -647,9 +614,8 @@ cm_dealloc(classmethod *cm)
 static int
 cm_traverse(classmethod *cm, visitproc visit, void *arg)
 {
-	if (!cm->cm_callable)
-		return 0;
-	return visit(cm->cm_callable, arg);
+	Py_VISIT(cm->cm_callable);
+	return 0;
 }
 
 static int
@@ -806,9 +772,8 @@ sm_dealloc(staticmethod *sm)
 static int
 sm_traverse(staticmethod *sm, visitproc visit, void *arg)
 {
-	if (!sm->sm_callable)
-		return 0;
-	return visit(sm->sm_callable, arg);
+	Py_VISIT(sm->sm_callable);
+	return 0;
 }
 
 static int
diff --git a/Objects/iterobject.c b/Objects/iterobject.c
index 14cacc6938..cf839f4781 100644
--- a/Objects/iterobject.c
+++ b/Objects/iterobject.c
@@ -38,9 +38,8 @@ iter_dealloc(seqiterobject *it)
 static int
 iter_traverse(seqiterobject *it, visitproc visit, void *arg)
 {
-	if (it->it_seq == NULL)
-		return 0;
-	return visit(it->it_seq, arg);
+	Py_VISIT(it->it_seq);
+	return 0;
 }
 
 static PyObject *
@@ -162,11 +161,8 @@ calliter_dealloc(calliterobject *it)
 static int
 calliter_traverse(calliterobject *it, visitproc visit, void *arg)
 {
-	int err;
-	if (it->it_callable != NULL && (err = visit(it->it_callable, arg)))
-		return err;
-	if (it->it_sentinel != NULL && (err = visit(it->it_sentinel, arg)))
-		return err;
+	Py_VISIT(it->it_callable);
+	Py_VISIT(it->it_sentinel);
 	return 0;
 }
 
diff --git a/Objects/listobject.c b/Objects/listobject.c
index 1debd23791..78961f33da 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -2276,14 +2276,8 @@ list_traverse(PyListObject *o, visitproc visit, void *arg)
 	Py_ssize_t i;
 	PyObject *x;
 
-	for (i = o->ob_size; --i >= 0; ) {
-		x = o->ob_item[i];
-		if (x != NULL) {
-			int err = visit(x, arg);
-			if (err)
-				return err;
-		}
-	}
+	for (i = o->ob_size; --i >= 0; )
+		Py_VISIT(o->ob_item[i]);
 	return 0;
 }
 
@@ -2779,9 +2773,8 @@ listiter_dealloc(listiterobject *it)
 static int
 listiter_traverse(listiterobject *it, visitproc visit, void *arg)
 {
-	if (it->it_seq == NULL)
-		return 0;
-	return visit((PyObject *)it->it_seq, arg);
+	Py_VISIT(it->it_seq);
+	return 0;
 }
 
 static PyObject *
@@ -2898,9 +2891,8 @@ listreviter_dealloc(listreviterobject *it)
 static int
 listreviter_traverse(listreviterobject *it, visitproc visit, void *arg)
 {
-	if (it->it_seq == NULL)
-		return 0;
-	return visit((PyObject *)it->it_seq, arg);
+	Py_VISIT(it->it_seq);
+	return 0;
 }
 
 static PyObject *
diff --git a/Objects/methodobject.c b/Objects/methodobject.c
index 8e3bf867ca..ecc9a0ab52 100644
--- a/Objects/methodobject.c
+++ b/Objects/methodobject.c
@@ -149,17 +149,8 @@ meth_get__name__(PyCFunctionObject *m, void *closure)
 static int
 meth_traverse(PyCFunctionObject *m, visitproc visit, void *arg)
 {
-	int err;
-	if (m->m_self != NULL) {
-		err = visit(m->m_self, arg);
-		if (err)
-			return err;
-	}
-	if (m->m_module != NULL) {
-		err = visit(m->m_module, arg);
-		if (err)
-			return err;
-	}
+	Py_VISIT(m->m_self);
+	Py_VISIT(m->m_module);
 	return 0;
 }
 
diff --git a/Objects/moduleobject.c b/Objects/moduleobject.c
index 812496806b..e454fcf321 100644
--- a/Objects/moduleobject.c
+++ b/Objects/moduleobject.c
@@ -204,8 +204,7 @@ module_repr(PyModuleObject *m)
 static int
 module_traverse(PyModuleObject *m, visitproc visit, void *arg)
 {
-	if (m->md_dict != NULL)
-		return visit(m->md_dict, arg);
+	Py_VISIT(m->md_dict);
 	return 0;
 }
 
diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index 10b7aaffbf..2161ab9ec1 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -438,16 +438,9 @@ static int
 tupletraverse(PyTupleObject *o, visitproc visit, void *arg)
 {
 	Py_ssize_t i;
-	PyObject *x;
-
-	for (i = o->ob_size; --i >= 0; ) {
-		x = o->ob_item[i];
-		if (x != NULL) {
-			int err = visit(x, arg);
-			if (err)
-				return err;
-		}
-	}
+
+	for (i = o->ob_size; --i >= 0; )
+		Py_VISIT(o->ob_item[i]);
 	return 0;
 }
 
@@ -802,9 +795,8 @@ tupleiter_dealloc(tupleiterobject *it)
 static int
 tupleiter_traverse(tupleiterobject *it, visitproc visit, void *arg)
 {
-	if (it->it_seq == NULL)
-		return 0;
-	return visit((PyObject *)it->it_seq, arg);
+	Py_VISIT(it->it_seq);
+	return 0;
 }
 
 static PyObject *
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index a0af2c9b42..43f04694f9 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -525,21 +525,15 @@ subtype_traverse(PyObject *self, visitproc visit, void *arg)
 
 	if (type->tp_dictoffset != base->tp_dictoffset) {
 		PyObject **dictptr = _PyObject_GetDictPtr(self);
-		if (dictptr && *dictptr) {
-			int err = visit(*dictptr, arg);
-			if (err)
-				return err;
-		}
+		if (dictptr && *dictptr)
+			Py_VISIT(*dictptr);
 	}
 
-	if (type->tp_flags & Py_TPFLAGS_HEAPTYPE) {
+	if (type->tp_flags & Py_TPFLAGS_HEAPTYPE)
 		/* For a heaptype, the instances count as references
 		   to the type.  Traverse the type so the collector
 		   can find cycles involving this link. */
-		int err = visit((PyObject *)type, arg);
-		if (err)
-			return err;
-	}
+		Py_VISIT(type);
 
 	if (basetraverse)
 		return basetraverse(self, visit, arg);
@@ -2198,32 +2192,21 @@ PyDoc_STRVAR(type_doc,
 static int
 type_traverse(PyTypeObject *type, visitproc visit, void *arg)
 {
-	int err;
-
 	/* Because of type_is_gc(), the collector only calls this
 	   for heaptypes. */
 	assert(type->tp_flags & Py_TPFLAGS_HEAPTYPE);
 
-#define VISIT(SLOT) \
-	if (SLOT) { \
-		err = visit((PyObject *)(SLOT), arg); \
-		if (err) \
-			return err; \
-	}
-
-	VISIT(type->tp_dict);
-	VISIT(type->tp_cache);
-	VISIT(type->tp_mro);
-	VISIT(type->tp_bases);
-	VISIT(type->tp_base);
+	Py_VISIT(type->tp_dict);
+	Py_VISIT(type->tp_cache);
+	Py_VISIT(type->tp_mro);
+	Py_VISIT(type->tp_bases);
+	Py_VISIT(type->tp_base);
 
 	/* There's no need to visit type->tp_subclasses or
 	   ((PyHeapTypeObject *)type)->ht_slots, because they can't be involved
 	   in cycles; tp_subclasses is a list of weak references,
 	   and slots is a tuple of strings. */
 
-#undef VISIT
-
 	return 0;
 }
 
@@ -5805,20 +5788,10 @@ static int
 super_traverse(PyObject *self, visitproc visit, void *arg)
 {
 	superobject *su = (superobject *)self;
-	int err;
-
-#define VISIT(SLOT) \
-	if (SLOT) { \
-		err = visit((PyObject *)(SLOT), arg); \
-		if (err) \
-			return err; \
-	}
-
-	VISIT(su->obj);
-	VISIT(su->type);
-	VISIT(su->obj_type);
 
-#undef VISIT
+	Py_VISIT(su->obj);
+	Py_VISIT(su->type);
+	Py_VISIT(su->obj_type);
 
 	return 0;
 }
diff --git a/Objects/weakrefobject.c b/Objects/weakrefobject.c
index a116efc863..a8ab56ecd8 100644
--- a/Objects/weakrefobject.c
+++ b/Objects/weakrefobject.c
@@ -109,8 +109,7 @@ weakref_dealloc(PyObject *self)
 static int
 gc_traverse(PyWeakReference *self, visitproc visit, void *arg)
 {
-    if (self->wr_callback != NULL)
-        return visit(self->wr_callback, arg);
+    Py_VISIT(self->wr_callback);
     return 0;
 }