gh-100720: refactor calculation of number of frame slots for a code object into the new function _PyFrame_NumSlotsForCodeObject

Include/internal/pycore_frame.h

@@ -92,7 +92,16 @@ static inline void _PyFrame_StackPush(_PyInterpreterFrame *f, PyObject *value) {
     f->stacktop++;
 }
 
-#define FRAME_SPECIALS_SIZE ((sizeof(_PyInterpreterFrame)-1)/sizeof(PyObject *))
+#define FRAME_SPECIALS_SIZE ((int)((sizeof(_PyInterpreterFrame)-1)/sizeof(PyObject *)))
+
+static inline int
+_PyFrame_NumSlotsForCodeObject(PyCodeObject *code)
+{
+    /* This function needs to remain in sync with the calculation of
+     * co_framesize in Tools/build/deepfreeze.py */
+    assert(code->co_framesize >= FRAME_SPECIALS_SIZE);
+    return code->co_framesize - FRAME_SPECIALS_SIZE;
+}
 
 void _PyFrame_Copy(_PyInterpreterFrame *src, _PyInterpreterFrame *dest);
 

Misc/NEWS.d/next/Core and Builtins/2023-01-03-16-50-42.gh-issue-100720.UhE7P-.rst

@@ -0,0 +1 @@
+Added ``_PyFrame_NumSlotsForCodeObject``, which returns the number of slots needed in a frame for a given code object.

Objects/frameobject.c

@@ -946,7 +946,7 @@ frame_sizeof(PyFrameObject *f, PyObject *Py_UNUSED(ignored))
     Py_ssize_t res;
     res = offsetof(PyFrameObject, _f_frame_data) + offsetof(_PyInterpreterFrame, localsplus);
     PyCodeObject *code = f->f_frame->f_code;
-    res += (code->co_nlocalsplus+code->co_stacksize) * sizeof(PyObject *);
+    res += _PyFrame_NumSlotsForCodeObject(code) * sizeof(PyObject *);
     return PyLong_FromSsize_t(res);
 }
 

Objects/genobject.c

@@ -769,7 +769,7 @@ gen_sizeof(PyGenObject *gen, PyObject *Py_UNUSED(ignored))
     Py_ssize_t res;
     res = offsetof(PyGenObject, gi_iframe) + offsetof(_PyInterpreterFrame, localsplus);
     PyCodeObject *code = gen->gi_code;
-    res += (code->co_nlocalsplus+code->co_stacksize) * sizeof(PyObject *);
+    res += _PyFrame_NumSlotsForCodeObject(code) * sizeof(PyObject *);
     return PyLong_FromSsize_t(res);
 }
 
@@ -850,7 +850,7 @@ static PyObject *
 make_gen(PyTypeObject *type, PyFunctionObject *func)
 {
     PyCodeObject *code = (PyCodeObject *)func->func_code;
-    int slots = code->co_nlocalsplus + code->co_stacksize;
+    int slots = _PyFrame_NumSlotsForCodeObject(code);
     PyGenObject *gen = PyObject_GC_NewVar(PyGenObject, type, slots);
     if (gen == NULL) {
         return NULL;

Tools/build/deepfreeze.py

@@ -262,6 +262,7 @@ def generate_code(self, name: str, code: types.CodeType) -> str:
             self.field(code, "co_argcount")
             self.field(code, "co_posonlyargcount")
             self.field(code, "co_kwonlyargcount")
+            # The following should remain in sync with _PyFrame_NumSlotsForCodeObject
             self.write(f".co_framesize = {code.co_stacksize + len(localsplusnames)} + FRAME_SPECIALS_SIZE,")
             self.field(code, "co_stacksize")
             self.field(code, "co_firstlineno")