Mark statically allocated objects

Author: markshannon

Include/internal/pycore_object.h

@@ -73,14 +73,24 @@ PyAPI_FUNC(int) _PyObject_IsFreed(PyObject *);
 #define _PyObject_HEAD_INIT(type)                   \
     {                                               \
         .ob_ref_local = _Py_IMMORTAL_REFCNT_LOCAL,  \
+        .ob_flags = _Py_STATICALLY_ALLOCATED_FLAG,  \
         .ob_type = (type)                           \
     }
 #else
+#if SIZEOF_VOID_P > 4
 #define _PyObject_HEAD_INIT(type)         \
     {                                     \
-        .ob_refcnt = _Py_IMMORTAL_INITIAL_REFCNT, \
+        .ob_refcnt = _Py_IMMORTAL_INITIAL_REFCNT,  \
+        .ob_flags = _Py_STATICALLY_ALLOCATED_FLAG, \
         .ob_type = (type)                 \
     }
+#else
+#define _PyObject_HEAD_INIT(type)         \
+    {                                     \
+        .ob_refcnt = _Py_STATIC_IMMORTAL_INITIAL_REFCNT, \
+        .ob_type = (type)                 \
+    }
+#endif
 #endif
 #define _PyVarObject_HEAD_INIT(type, size)    \
     {                                         \

Include/object.h

@@ -152,7 +152,7 @@ struct _object {
     // trashcan mechanism as a linked list pointer and by the GC to store the
     // computed "gc_refs" refcount.
     uintptr_t ob_tid;
-    uint16_t _padding;
+    uint16_t ob_flags;
     PyMutex ob_mutex;           // per-object lock
     uint8_t ob_gc_bits;         // gc-related state
     uint32_t ob_ref_local;      // local reference count

Include/refcount.h

@@ -54,10 +54,15 @@ immortality, but the execution would still be correct.
 Reference count increases and decreases will first go through an immortality
 check by comparing the reference count field to the minimum immortality refcount.
 */
-#define _Py_IMMORTAL_INITIAL_REFCNT ((Py_ssize_t)(3L << 29))
+#define _Py_IMMORTAL_INITIAL_REFCNT ((Py_ssize_t)(5L << 28))
 #define _Py_IMMORTAL_MINIMUM_REFCNT ((Py_ssize_t)(1L << 30))
+#define _Py_STATIC_IMMORTAL_INITIAL_REFCNT ((Py_ssize_t)(7L << 28))
+#define _Py_STATIC_IMMORTAL_MINIMUM_REFCNT ((Py_ssize_t)(6L << 28))
 #endif
 
+/* Leave the low bits for refcount overflow for old stable ABI code */
+#define _Py_STATICALLY_ALLOCATED_FLAG (1 << 7)
+
 // Py_GIL_DISABLED builds indicate immortal objects using `ob_ref_local`, which is
 // always 32-bits.
 #ifdef Py_GIL_DISABLED
@@ -123,6 +128,16 @@ static inline Py_ALWAYS_INLINE int _Py_IsImmortal(PyObject *op)
 #define _Py_IsImmortal(op) _Py_IsImmortal(_PyObject_CAST(op))
 
 
+static inline Py_ALWAYS_INLINE int _Py_IsStaticImmortal(PyObject *op)
+{
+#if defined(Py_GIL_DISABLED) || SIZEOF_VOID_P > 4
+    return (op->ob_flags & _Py_STATICALLY_ALLOCATED_FLAG) != 0;
+#else
+    return op->ob_refcnt >= _Py_STATIC_IMMORTAL_MINIMUM_REFCNT;
+#endif
+}
+#define _Py_IsStaticImmortal(op) _Py_IsStaticImmortal(_PyObject_CAST(op))
+
 // Py_SET_REFCNT() implementation for stable ABI
 PyAPI_FUNC(void) _Py_SetRefcnt(PyObject *ob, Py_ssize_t refcnt);