Handle statically-allocated PyTypeObjects by having the collector keep a list of them.

Even with some optimizations it seems to hurt perf a little bit...
we'll have to see if it's worth it.

Also, rename "static roots" to "permanent roots", since it's
slightly different than the "static allocation" problem we're
tackling here.

src/gc/collector.cpp

@@ -37,31 +37,46 @@ namespace pyston {
 namespace gc {
 
 static TraceStack roots;
-void registerStaticRootObj(void* obj) {
+void registerPermanentRoot(void* obj) {
     assert(global_heap.getAllocationFromInteriorPointer(obj));
     roots.push(obj);
+
+#ifndef NDEBUG
+    // Check for double-registers.  Wouldn't cause any problems, but we probably shouldn't be doing them.
+    static std::unordered_set<void*> roots;
+    ASSERT(roots.count(obj) == 0, "Please only register roots once");
+    roots.insert(obj);
+#endif
 }
 
-std::vector<std::pair<void*, void*> > static_root_memory;
-void registerStaticRootMemory(void* start, void* end) {
-    assert(start < end);
+static std::unordered_set<void*> nonheap_roots;
+// Track the highest-addressed nonheap root; the assumption is that the nonheap roots will
+// typically all have lower addresses than the heap roots, so this can serve as a cheap
+// way to verify it's not a nonheap root (the full check requires a hashtable lookup).
+static void* max_nonheap_root = 0;
+void registerNonheapRootObject(void* obj) {
+    // I suppose that things could work fine even if this were true, but why would it happen?
+    assert(global_heap.getAllocationFromInteriorPointer(obj) == NULL);
+    assert(nonheap_roots.count(obj) == 0);
 
-    // While these aren't necessary to work correctly, they are the anticipated use case:
-    assert(global_heap.getAllocationFromInteriorPointer(start) == NULL);
-    assert(global_heap.getAllocationFromInteriorPointer(end) == NULL);
+    nonheap_roots.insert(obj);
 
-    static_root_memory.push_back(std::make_pair(start, end));
+    max_nonheap_root = std::max(obj, max_nonheap_root);
 }
 
-static std::unordered_set<StaticRootHandle*>* getRootHandles() {
-    static std::unordered_set<StaticRootHandle*> root_handles;
+static bool isNonheapRoot(void* p) {
+    return p <= max_nonheap_root && nonheap_roots.count(p) != 0;
+}
+
+static std::unordered_set<GCRootHandle*>* getRootHandles() {
+    static std::unordered_set<GCRootHandle*> root_handles;
     return &root_handles;
 }
 
-StaticRootHandle::StaticRootHandle() {
+GCRootHandle::GCRootHandle() {
     getRootHandles()->insert(this);
 }
-StaticRootHandle::~StaticRootHandle() {
+GCRootHandle::~GCRootHandle() {
     getRootHandles()->erase(this);
 }
 
@@ -72,19 +87,19 @@ bool TraceStackGCVisitor::isValid(void* p) {
 }
 
 void TraceStackGCVisitor::visit(void* p) {
-    assert(global_heap.getAllocationFromInteriorPointer(p)->user_data == p);
-    stack->push(p);
+    if (isNonheapRoot(p)) {
+        return;
+    } else {
+        assert(global_heap.getAllocationFromInteriorPointer(p)->user_data == p);
+        stack->push(p);
+    }
 }
 
 void TraceStackGCVisitor::visitRange(void* const* start, void* const* end) {
-#ifndef NDEBUG
-    void* const* cur = start;
-    while (cur < end) {
-        assert(isValid(*cur));
-        cur++;
+    while (start < end) {
+        visit(*start);
+        start++;
     }
-#endif
-    stack->pushall(start, end);
 }
 
 void TraceStackGCVisitor::visitPotential(void* p) {
@@ -113,8 +128,14 @@ static void markPhase() {
 
     TraceStackGCVisitor visitor(&stack);
 
-    for (const auto& p : static_root_memory) {
-        visitor.visitPotentialRange((void**)p.first, (void**)p.second);
+    for (void* p : nonheap_roots) {
+        Box* b = reinterpret_cast<Box*>(p);
+        BoxedClass* cls = b->cls;
+
+        if (cls) {
+            ASSERT(cls->gc_visit, "%s", getTypeName(b)->c_str());
+            cls->gc_visit(&visitor, b);
+        }
     }
 
     for (auto h : *getRootHandles()) {

src/gc/collector.h

@@ -27,7 +27,7 @@ private:
     std::vector<void*> v;
 
 public:
-    void pushall(void* const* start, void* const* end) { v.insert(v.end(), start, end); }
+    template <typename T> void pushall(T start, T end) { v.insert(v.end(), start, end); }
 
     void push(void* p) { v.push_back(p); }
 
@@ -62,25 +62,27 @@ public:
 
 // Mark this gc-allocated object as being a root, even if there are no visible references to it.
 // (Note: this marks the gc allocation itself, not the pointer that points to one.  For that, use
-// a StaticRootHandle or registerStaticRootMemory)
-void registerStaticRootObj(void* root_obj);
-// Register a non-gc region of memory (such as statically-allocated memory) as a source of potential
-// GC roots.
-void registerStaticRootMemory(void* start, void* end);
-void runCollection();
+// a GCRootHandle)
+void registerPermanentRoot(void* root_obj);
+// Register an object that was not allocated through this collector, as a root for this collector.
+// The motivating usecase is statically-allocated PyTypeObject objects, which are full Python objects
+// even if they are not heap allocated.
+void registerNonheapRootObject(void* obj);
 
 // If you want to have a static root "location" where multiple values could be stored, use this:
-class StaticRootHandle {
+class GCRootHandle {
 public:
     Box* value;
 
-    StaticRootHandle();
-    ~StaticRootHandle();
+    GCRootHandle();
+    ~GCRootHandle();
 
     void operator=(Box* b) { value = b; }
 
     operator Box*() { return value; }
 };
+
+void runCollection();
 }
 }
 

src/runtime/bool.cpp

@@ -71,8 +71,8 @@ void setupBool() {
     True = new BoxedBool(true);
     False = new BoxedBool(false);
 
-    gc::registerStaticRootObj(True);
-    gc::registerStaticRootObj(False);
+    gc::registerPermanentRoot(True);
+    gc::registerPermanentRoot(False);
 }
 
 void teardownBool() {

src/runtime/builtin_modules/builtins.cpp

@@ -528,7 +528,7 @@ void setupBuiltins() {
     notimplemented_cls->giveAttr("__repr__", new BoxedFunction(boxRTFunction((void*)notimplementedRepr, STR, 1)));
     notimplemented_cls->freeze();
     NotImplemented = new Box(notimplemented_cls);
-    gc::registerStaticRootObj(NotImplemented);
+    gc::registerPermanentRoot(NotImplemented);
 
     builtins_module->giveAttr("NotImplemented", NotImplemented);
     builtins_module->giveAttr("NotImplementedType", notimplemented_cls);

src/runtime/builtin_modules/sys.cpp

@@ -101,7 +101,7 @@ public:
 
 void setupSys() {
     sys_modules_dict = new BoxedDict();
-    gc::registerStaticRootObj(sys_modules_dict);
+    gc::registerPermanentRoot(sys_modules_dict);
 
     // This is ok to call here because we've already created the sys_modules_dict
     sys_module = createModule("sys", "__builtin__");

src/runtime/capi.cpp

@@ -201,7 +201,7 @@ extern "C" void conservativeGCHandler(GCVisitor* v, Box* b) {
 }
 
 extern "C" int PyType_Ready(PyTypeObject* cls) {
-    gc::registerStaticRootMemory(cls, cls + 1);
+    gc::registerNonheapRootObject(cls);
 
     // unhandled fields:
     RELEASE_ASSERT(cls->tp_print == NULL, "");

src/runtime/dict.cpp

@@ -263,7 +263,6 @@ void setupDict() {
 
     dict_cls->freeze();
 
-    gc::registerStaticRootObj(dict_iterator_cls);
     dict_iterator_cls->giveAttr("__name__", boxStrConstant("dictiterator"));
 
     CLFunction* hasnext = boxRTFunction((void*)dictIterHasnextUnboxed, BOOL, 1);

src/runtime/generator.cpp

@@ -190,7 +190,6 @@ void setupGenerator() {
     generator_cls->giveAttr("send", new BoxedFunction(boxRTFunction((void*)generatorSend, UNKNOWN, 2)));
     generator_cls->giveAttr("throw", new BoxedFunction(boxRTFunction((void*)generatorThrow, UNKNOWN, 2)));
 
-    gc::registerStaticRootObj(generator_cls);
     generator_cls->freeze();
 }
 }

src/runtime/int.cpp

@@ -659,7 +659,7 @@ static void _addFuncIntUnknown(const char* name, ConcreteCompilerType* rtn_type,
 void setupInt() {
     for (int i = 0; i < NUM_INTERNED_INTS; i++) {
         interned_ints[i] = new BoxedInt(int_cls, i);
-        gc::registerStaticRootObj(interned_ints[i]);
+        gc::registerPermanentRoot(interned_ints[i]);
     }
 
     int_cls->giveAttr("__name__", boxStrConstant("int"));

src/runtime/list.cpp

@@ -575,7 +575,6 @@ void setupList() {
     list_cls->freeze();
 
 
-    gc::registerStaticRootObj(list_iterator_cls);
     list_iterator_cls->giveAttr("__name__", boxStrConstant("listiterator"));
 
     CLFunction* hasnext = boxRTFunction((void*)listiterHasnextUnboxed, BOOL, 1);

src/runtime/objmodel.cpp

@@ -413,7 +413,7 @@ BoxedClass::BoxedClass(BoxedClass* base, gcvisit_func gc_visit, int attrs_offset
     }
 
     if (!is_user_defined)
-        gc::registerStaticRootObj(this);
+        gc::registerPermanentRoot(this);
 }
 
 extern "C" const std::string* getNameOfClass(BoxedClass* cls) {
@@ -696,7 +696,7 @@ static Box* _handleClsAttr(Box* obj, Box* attr) {
                 return boxBool(rtn);
             }
             case BoxedMemberDescriptor::INT: {
-                int rtn = reinterpret_cast<int*>(obj)[member_desc->offset/sizeof(int)];
+                int rtn = reinterpret_cast<int*>(obj)[member_desc->offset / sizeof(int)];
                 return boxInt(rtn);
             }
             default:

src/runtime/set.cpp

@@ -213,7 +213,6 @@ void setupSet() {
                                new BoxedFunction(boxRTFunction((void*)setiteratorHasnext, BOXED_BOOL, 1)));
     set_iterator_cls->giveAttr("next", new BoxedFunction(boxRTFunction((void*)setiteratorNext, UNKNOWN, 1)));
     set_iterator_cls->freeze();
-    gc::registerStaticRootObj(set_iterator_cls);
 
     set_cls->giveAttr("__new__",
                       new BoxedFunction(boxRTFunction((void*)setNew, UNKNOWN, 2, 1, false, false), { None }));

src/runtime/stacktrace.cpp

@@ -102,7 +102,7 @@ void unwindExc(Box* exc_obj) {
 }
 
 static std::vector<const LineInfo*> getTracebackEntries();
-static gc::StaticRootHandle last_exc;
+static gc::GCRootHandle last_exc;
 static std::vector<const LineInfo*> last_tb;
 
 void raiseRaw(Box* exc_obj) __attribute__((__noreturn__));

src/runtime/str.cpp

@@ -784,7 +784,6 @@ Box* strCount2(BoxedString* self, Box* elt) {
 
 void setupStr() {
     str_iterator_cls = new BoxedClass(object_cls, &strIteratorGCHandler, 0, sizeof(BoxedString), false);
-    gc::registerStaticRootObj(str_iterator_cls);
     str_iterator_cls->giveAttr("__name__", boxStrConstant("striterator"));
     str_iterator_cls->giveAttr("__hasnext__",
                                new BoxedFunction(boxRTFunction((void*)BoxedStringIterator::hasnext, BOXED_BOOL, 1)));

src/runtime/tuple.cpp

@@ -329,7 +329,6 @@ void setupTuple() {
 
     tuple_cls->freeze();
 
-    gc::registerStaticRootObj(tuple_iterator_cls);
     tuple_iterator_cls->giveAttr("__name__", boxStrConstant("tupleiterator"));
 
     CLFunction* hasnext = boxRTFunction((void*)tupleiterHasnextUnboxed, BOOL, 1);

src/runtime/types.cpp

@@ -183,7 +183,7 @@ extern "C" void boxGCHandler(GCVisitor* v, Box* b) {
                 HCAttrs::AttrList* attr_list = attrs->attr_list;
                 assert(attr_list);
                 v->visit(attr_list);
-                v->visitPotentialRange((void**)&attr_list->attrs[0], (void**)&attr_list->attrs[nattrs]);
+                v->visitRange((void**)&attr_list->attrs[0], (void**)&attr_list->attrs[nattrs]);
             }
         }
     } else {
@@ -584,7 +584,7 @@ Box* objectStr(Box* obj) {
 bool TRACK_ALLOCATIONS = false;
 void setupRuntime() {
     root_hcls = HiddenClass::makeRoot();
-    gc::registerStaticRootObj(root_hcls);
+    gc::registerPermanentRoot(root_hcls);
 
     object_cls = new BoxedClass(NULL, &boxGCHandler, 0, sizeof(Box), false);
     type_cls = new BoxedClass(object_cls, &typeGCHandler, offsetof(BoxedClass, attrs), sizeof(BoxedClass), false);
@@ -593,7 +593,7 @@ void setupRuntime() {
 
     none_cls = new BoxedClass(object_cls, NULL, 0, sizeof(Box), false);
     None = new Box(none_cls);
-    gc::registerStaticRootObj(None);
+    gc::registerPermanentRoot(None);
 
     // TODO we leak all the string data!
     str_cls = new BoxedClass(object_cls, NULL, 0, sizeof(BoxedString), false);
@@ -607,7 +607,7 @@ void setupRuntime() {
 
     tuple_cls = new BoxedClass(object_cls, &tupleGCHandler, 0, sizeof(BoxedTuple), false);
     EmptyTuple = new BoxedTuple({});
-    gc::registerStaticRootObj(EmptyTuple);
+    gc::registerPermanentRoot(EmptyTuple);
 
 
     module_cls = new BoxedClass(object_cls, NULL, offsetof(BoxedModule, attrs), sizeof(BoxedModule), false);

src/runtime/types.h

@@ -331,7 +331,8 @@ public:
     int offset;
 
     BoxedMemberDescriptor(MemberType type, int offset) : Box(member_cls), type(type), offset(offset) {}
-    BoxedMemberDescriptor(PyMemberDef* member) : Box(member_cls), type((MemberType)member->type), offset(member->offset) {}
+    BoxedMemberDescriptor(PyMemberDef* member)
+        : Box(member_cls), type((MemberType)member->type), offset(member->offset) {}
 };
 
 // TODO is there any particular reason to make this a Box, ie a python-level object?