Update isValidGCObject to check the allocation kind

ie make sure both that it's a valid allocation, but also that
it will have Python destructor semantics applied when it is freed
(as opposed to, say, STLCompatAllocator-allocated memory).

This is to make sure that extension modules don't use a different
allocation routine than we expected.

There are only a few specialized places that I could find that we
actually want the old-behavior; in dump(), and in PyObject_Init right
before we call setIsPythonObject.  So for those cases, add a new
isValidGCMemory call that doesn't do the allocation-kind check.

src/gc/collector.cpp

@@ -180,10 +180,19 @@ bool isNonheapRoot(void* p) {
     return nonheap_roots.count(p) != 0;
 }
 
-bool isValidGCObject(void* p) {
+bool isValidGCMemory(void* p) {
     return isNonheapRoot(p) || (global_heap.getAllocationFromInteriorPointer(p)->user_data == p);
 }
 
+bool isValidGCObject(void* p) {
+    if (isNonheapRoot(p))
+        return true;
+    GCAllocation* al = global_heap.getAllocationFromInteriorPointer(p);
+    if (!al)
+        return false;
+    return al->user_data == p && (al->kind_id == GCKind::CONSERVATIVE_PYTHON || al->kind_id == GCKind::PYTHON);
+}
+
 void setIsPythonObject(Box* b) {
     auto al = global_heap.getAllocationFromInteriorPointer(b);
     assert(al->user_data == (char*)b);

src/gc/collector.h

@@ -60,7 +60,8 @@ void disableGC();
 void enableGC();
 
 // These are mostly for debugging:
-bool isValidGCObject(void* p);
+bool isValidGCMemory(void* p); // if p is a valid gc-allocated pointer (or a non-heap root)
+bool isValidGCObject(void* p); // whether p is valid gc memory and is set to have Python destructor semantics applied
 bool isNonheapRoot(void* p);
 void setIsPythonObject(Box* b);
 

src/runtime/capi.cpp

@@ -1645,7 +1645,7 @@ static Box* methodGetDoc(Box* b, void*) {
 
 extern "C" PyObject* _PyObject_GC_Malloc(size_t basicsize) noexcept {
     Box* r = ((PyObject*)PyObject_MALLOC(basicsize));
-    RELEASE_ASSERT(gc::isValidGCObject(r), "");
+    RELEASE_ASSERT(gc::isValidGCMemory(r), "");
     return r;
 }
 

src/runtime/objmodel.cpp

@@ -2338,7 +2338,7 @@ extern "C" void dumpEx(void* p, int levels) {
     printf("\n");
     printf("Raw address: %p\n", p);
 
-    bool is_gc = gc::isValidGCObject(p);
+    bool is_gc = gc::isValidGCMemory(p);
     if (!is_gc) {
         printf("non-gc memory\n");
         return;

src/runtime/types.cpp

@@ -2233,11 +2233,11 @@ inline void initUserAttrs(Box* obj, BoxedClass* cls) {
 extern "C" void PyCallIter_AddHasNext();
 
 extern "C" PyVarObject* PyObject_InitVar(PyVarObject* op, PyTypeObject* tp, Py_ssize_t size) noexcept {
-    assert(gc::isValidGCObject(op));
-    assert(gc::isValidGCObject(tp));
+    assert(op);
+    assert(tp);
 
-    RELEASE_ASSERT(op, "");
-    RELEASE_ASSERT(tp, "");
+    assert(gc::isValidGCMemory(op));
+    assert(gc::isValidGCObject(tp));
 
     gc::setIsPythonObject(op);
 
@@ -2251,7 +2251,7 @@ extern "C" PyObject* PyObject_Init(PyObject* op, PyTypeObject* tp) noexcept {
     assert(op);
     assert(tp);
 
-    assert(gc::isValidGCObject(op));
+    assert(gc::isValidGCMemory(op));
     assert(gc::isValidGCObject(tp));
 
     gc::setIsPythonObject(op);