gh-126596: Use PyObject_VAR_HEAD for generator objects

Include/internal/pycore_genobject.h

@@ -13,7 +13,7 @@ extern "C" {
 /* _PyGenObject_HEAD defines the initial segment of generator
    and coroutine objects. */
 #define _PyGenObject_HEAD(prefix)                                           \
-    PyObject_HEAD                                                           \
+    PyObject_VAR_HEAD                                                       \
     /* List of weak reference. */                                           \
     PyObject *prefix##_weakreflist;                                         \
     /* Name of the generator. */                                            \

Lib/test/test_sys.py

@@ -1640,8 +1640,10 @@ def bar(cls):
             # classmethod
             check(bar, size('PP'))
         # generator
-        def get_gen(): yield 1
-        check(get_gen(), size('6P4c' + INTERPRETER_FRAME + 'P'))
+        def get_gen1(): yield
+        check(get_gen1(), size('7P4c' + INTERPRETER_FRAME + 'P'))
+        def get_gen2():  _ = yield
+        check(get_gen2(), size('7P4c' + INTERPRETER_FRAME + 'PP'))
         # iterator
         check(iter('abc'), size('lP'))
         # callable-iterator

Misc/NEWS.d/next/Core_and_Builtins/2024-11-18-22-29-58.gh-issue-126596.66G_sl.rst

@@ -0,0 +1,10 @@
+Generator objects now have a valid ``ob_size`` field.
+
+#.. section: Library #.. section: Documentation #.. section: Tests #..
+section: Build #.. section: Windows #.. section: macOS #.. section: IDLE #..
+section: Tools/Demos #.. section: C API
+
+# Write your Misc/NEWS.d entry below.  It should be a simple ReST paragraph.
+# Don't start with "- Issue #<n>: " or "- gh-issue-<n>: " or that sort of
+stuff.
+###########################################################################

Objects/genobject.c

@@ -814,24 +814,10 @@ static PyMemberDef gen_memberlist[] = {
     {NULL}      /* Sentinel */
 };
 
-static PyObject *
-gen_sizeof(PyGenObject *gen, PyObject *Py_UNUSED(ignored))
-{
-    Py_ssize_t res;
-    res = offsetof(PyGenObject, gi_iframe) + offsetof(_PyInterpreterFrame, localsplus);
-    PyCodeObject *code = _PyGen_GetCode(gen);
-    res += _PyFrame_NumSlotsForCodeObject(code) * sizeof(PyObject *);
-    return PyLong_FromSsize_t(res);
-}
-
-PyDoc_STRVAR(sizeof__doc__,
-"gen.__sizeof__() -> size of gen in memory, in bytes");
-
 static PyMethodDef gen_methods[] = {
     {"send", gen_send, METH_O, send_doc},
     {"throw", _PyCFunction_CAST(gen_throw), METH_FASTCALL, throw_doc},
     {"close", gen_close, METH_NOARGS, close_doc},
-    {"__sizeof__", (PyCFunction)gen_sizeof, METH_NOARGS, sizeof__doc__},
     {"__class_getitem__", Py_GenericAlias, METH_O|METH_CLASS, PyDoc_STR("See PEP 585")},
     {NULL, NULL}        /* Sentinel */
 };
@@ -1192,7 +1178,6 @@ static PyMethodDef coro_methods[] = {
     {"send", gen_send, METH_O, coro_send_doc},
     {"throw",_PyCFunction_CAST(gen_throw), METH_FASTCALL, coro_throw_doc},
     {"close", gen_close, METH_NOARGS, coro_close_doc},
-    {"__sizeof__", (PyCFunction)gen_sizeof, METH_NOARGS, sizeof__doc__},
     {"__class_getitem__", Py_GenericAlias, METH_O|METH_CLASS, PyDoc_STR("See PEP 585")},
     {NULL, NULL}        /* Sentinel */
 };
@@ -1620,7 +1605,6 @@ static PyMethodDef async_gen_methods[] = {
     {"asend", (PyCFunction)async_gen_asend, METH_O, async_asend_doc},
     {"athrow",(PyCFunction)async_gen_athrow, METH_VARARGS, async_athrow_doc},
     {"aclose", (PyCFunction)async_gen_aclose, METH_NOARGS, async_aclose_doc},
-    {"__sizeof__", (PyCFunction)gen_sizeof, METH_NOARGS, sizeof__doc__},
     {"__class_getitem__",    Py_GenericAlias,
     METH_O|METH_CLASS,       PyDoc_STR("See PEP 585")},
     {NULL, NULL}        /* Sentinel */