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gh-103509: PEP 697 -- Limited C API for Extending Opaque Types (GH-103511)
Co-authored-by: Oleg Iarygin <oleg@arhadthedev.net> Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>
This commit is contained in:
Petr Viktorin
GitHub
parent
35d273825a
commit
cd9a56c2b0
30 changed files with 970 additions and 19 deletions
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@ -18,6 +18,7 @@
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#include "structmember.h" // PyMemberDef
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#include <ctype.h>
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#include <stddef.h> // ptrdiff_t
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/*[clinic input]
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class type "PyTypeObject *" "&PyType_Type"
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@ -1686,6 +1687,12 @@ PyType_GenericNew(PyTypeObject *type, PyObject *args, PyObject *kwds)
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/* Helpers for subtyping */
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static inline PyMemberDef *
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_PyHeapType_GET_MEMBERS(PyHeapTypeObject* type)
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{
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return PyObject_GetItemData((PyObject *)type);
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}
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static int
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traverse_slots(PyTypeObject *type, PyObject *self, visitproc visit, void *arg)
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{
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@ -3873,6 +3880,15 @@ static const PySlot_Offset pyslot_offsets[] = {
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#include "typeslots.inc"
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};
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/* Align up to the nearest multiple of alignof(max_align_t)
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* (like _Py_ALIGN_UP, but for a size rather than pointer)
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*/
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static Py_ssize_t
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_align_up(Py_ssize_t size)
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{
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return (size + ALIGNOF_MAX_ALIGN_T - 1) & ~(ALIGNOF_MAX_ALIGN_T - 1);
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}
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/* Given a PyType_FromMetaclass `bases` argument (NULL, type, or tuple of
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* types), return a tuple of types.
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*/
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@ -4013,6 +4029,20 @@ _PyType_FromMetaclass_impl(
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assert(memb->flags == READONLY);
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vectorcalloffset = memb->offset;
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}
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if (memb->flags & Py_RELATIVE_OFFSET) {
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if (spec->basicsize > 0) {
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PyErr_SetString(
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PyExc_SystemError,
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"With Py_RELATIVE_OFFSET, basicsize must be negative.");
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goto finally;
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}
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if (memb->offset < 0 || memb->offset >= -spec->basicsize) {
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PyErr_SetString(
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PyExc_SystemError,
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"Member offset out of range (0..-basicsize)");
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goto finally;
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}
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}
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}
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break;
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case Py_tp_doc:
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@ -4154,6 +4184,32 @@ _PyType_FromMetaclass_impl(
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// here we just check its work
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assert(_PyType_HasFeature(base, Py_TPFLAGS_BASETYPE));
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/* Calculate sizes */
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Py_ssize_t basicsize = spec->basicsize;
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Py_ssize_t type_data_offset = spec->basicsize;
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if (basicsize == 0) {
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/* Inherit */
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basicsize = base->tp_basicsize;
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}
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else if (basicsize < 0) {
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/* Extend */
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type_data_offset = _align_up(base->tp_basicsize);
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basicsize = type_data_offset + _align_up(-spec->basicsize);
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/* Inheriting variable-sized types is limited */
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if (base->tp_itemsize
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&& !((base->tp_flags | spec->flags) & Py_TPFLAGS_ITEMS_AT_END))
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{
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PyErr_SetString(
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PyExc_SystemError,
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"Cannot extend variable-size class without Py_TPFLAGS_ITEMS_AT_END.");
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goto finally;
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}
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}
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Py_ssize_t itemsize = spec->itemsize;
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/* Allocate the new type
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*
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* Between here and PyType_Ready, we should limit:
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@ -4201,8 +4257,8 @@ _PyType_FromMetaclass_impl(
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/* Copy the sizes */
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type->tp_basicsize = spec->basicsize;
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type->tp_itemsize = spec->itemsize;
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type->tp_basicsize = basicsize;
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type->tp_itemsize = itemsize;
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/* Copy all the ordinary slots */
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@ -4219,6 +4275,16 @@ _PyType_FromMetaclass_impl(
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size_t len = Py_TYPE(type)->tp_itemsize * nmembers;
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memcpy(_PyHeapType_GET_MEMBERS(res), slot->pfunc, len);
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type->tp_members = _PyHeapType_GET_MEMBERS(res);
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PyMemberDef *memb;
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Py_ssize_t i;
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for (memb = _PyHeapType_GET_MEMBERS(res), i = nmembers;
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i > 0; ++memb, --i)
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{
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if (memb->flags & Py_RELATIVE_OFFSET) {
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memb->flags &= ~Py_RELATIVE_OFFSET;
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memb->offset += type_data_offset;
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}
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}
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}
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break;
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default:
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@ -4227,6 +4293,7 @@ _PyType_FromMetaclass_impl(
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PySlot_Offset slotoffsets = pyslot_offsets[slot->slot];
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short slot_offset = slotoffsets.slot_offset;
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if (slotoffsets.subslot_offset == -1) {
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/* Set a slot in the main PyTypeObject */
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*(void**)((char*)res_start + slot_offset) = slot->pfunc;
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}
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else {
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@ -4461,6 +4528,34 @@ PyType_GetModuleByDef(PyTypeObject *type, PyModuleDef *def)
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return NULL;
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}
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void *
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PyObject_GetTypeData(PyObject *obj, PyTypeObject *cls)
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{
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assert(PyObject_TypeCheck(obj, cls));
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return (char *)obj + _align_up(cls->tp_base->tp_basicsize);
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}
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Py_ssize_t
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PyType_GetTypeDataSize(PyTypeObject *cls)
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{
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ptrdiff_t result = cls->tp_basicsize - _align_up(cls->tp_base->tp_basicsize);
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if (result < 0) {
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return 0;
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}
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return result;
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}
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void *
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PyObject_GetItemData(PyObject *obj)
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{
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if (!PyType_HasFeature(Py_TYPE(obj), Py_TPFLAGS_ITEMS_AT_END)) {
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PyErr_Format(PyExc_TypeError,
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"type '%s' does not have Py_TPFLAGS_ITEMS_AT_END",
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Py_TYPE(obj)->tp_name);
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return NULL;
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}
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return (char *)obj + Py_TYPE(obj)->tp_basicsize;
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}
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/* Internal API to look for a name through the MRO, bypassing the method cache.
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This returns a borrowed reference, and might set an exception.
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@ -5158,7 +5253,8 @@ PyTypeObject PyType_Type = {
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0, /* tp_as_buffer */
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
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Py_TPFLAGS_BASETYPE | Py_TPFLAGS_TYPE_SUBCLASS |
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Py_TPFLAGS_HAVE_VECTORCALL, /* tp_flags */
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Py_TPFLAGS_HAVE_VECTORCALL |
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Py_TPFLAGS_ITEMS_AT_END, /* tp_flags */
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type_doc, /* tp_doc */
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(traverseproc)type_traverse, /* tp_traverse */
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(inquiry)type_clear, /* tp_clear */
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@ -6572,9 +6668,14 @@ inherit_special(PyTypeObject *type, PyTypeObject *base)
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else if (PyType_IsSubtype(base, &PyDict_Type)) {
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type->tp_flags |= Py_TPFLAGS_DICT_SUBCLASS;
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}
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/* Setup some inheritable flags */
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if (PyType_HasFeature(base, _Py_TPFLAGS_MATCH_SELF)) {
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type->tp_flags |= _Py_TPFLAGS_MATCH_SELF;
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}
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if (PyType_HasFeature(base, Py_TPFLAGS_ITEMS_AT_END)) {
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type->tp_flags |= Py_TPFLAGS_ITEMS_AT_END;
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}
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}
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static int
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