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gh-123465: Allow Py_RELATIVE_OFFSET for __*offset__ members (GH-123474)

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Petr Viktorin 2024-09-05 14:14:05 +02:00 • committed by GitHub
parent ce9f84a47b
commit 16be8db6be
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8 changed files with 422 additions and 74 deletions
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85
Objects/typeobject.c
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@ -4642,6 +4642,41 @@ check_basicsize_includes_size_and_offsets(PyTypeObject* type)
return 1;
}
/* Set *dest to the offset specified by a special "__*offset__" member.
* Return 0 on success, -1 on failure.
*/
static inline int
special_offset_from_member(
const PyMemberDef *memb /* may be NULL */,
Py_ssize_t type_data_offset,
Py_ssize_t *dest /* not NULL */)
{
if (memb == NULL) {
*dest = 0;
return 0;
}
if (memb->type != Py_T_PYSSIZET) {
PyErr_Format(
PyExc_SystemError,
"type of %s must be Py_T_PYSSIZET",
memb->name);
return -1;
}
if (memb->flags == Py_READONLY) {
*dest = memb->offset;
return 0;
}
else if (memb->flags == (Py_READONLY | Py_RELATIVE_OFFSET)) {
*dest = memb->offset + type_data_offset;
return 0;
}
PyErr_Format(
PyExc_SystemError,
"flags for %s must be Py_READONLY or (Py_READONLY | Py_RELATIVE_OFFSET)",
memb->name);
return -1;
}
static PyObject *
_PyType_FromMetaclass_impl(
PyTypeObject *metaclass, PyObject *module,
@ -4667,10 +4702,11 @@ _PyType_FromMetaclass_impl(
const PyType_Slot *slot;
Py_ssize_t nmembers = 0;
Py_ssize_t weaklistoffset, dictoffset, vectorcalloffset;
const PyMemberDef *weaklistoffset_member = NULL;
const PyMemberDef *dictoffset_member = NULL;
const PyMemberDef *vectorcalloffset_member = NULL;
char *res_start;
nmembers = weaklistoffset = dictoffset = vectorcalloffset = 0;
for (slot = spec->slots; slot->slot; slot++) {
if (slot->slot < 0
|| (size_t)slot->slot >= Py_ARRAY_LENGTH(pyslot_offsets)) {
@ -4687,24 +4723,6 @@ _PyType_FromMetaclass_impl(
}
for (const PyMemberDef *memb = slot->pfunc; memb->name != NULL; memb++) {
nmembers++;
if (strcmp(memb->name, "__weaklistoffset__") == 0) {
// The PyMemberDef must be a Py_ssize_t and readonly
assert(memb->type == Py_T_PYSSIZET);
assert(memb->flags == Py_READONLY);
weaklistoffset = memb->offset;
}
if (strcmp(memb->name, "__dictoffset__") == 0) {
// The PyMemberDef must be a Py_ssize_t and readonly
assert(memb->type == Py_T_PYSSIZET);
assert(memb->flags == Py_READONLY);
dictoffset = memb->offset;
}
if (strcmp(memb->name, "__vectorcalloffset__") == 0) {
// The PyMemberDef must be a Py_ssize_t and readonly
assert(memb->type == Py_T_PYSSIZET);
assert(memb->flags == Py_READONLY);
vectorcalloffset = memb->offset;
}
if (memb->flags & Py_RELATIVE_OFFSET) {
if (spec->basicsize > 0) {
PyErr_SetString(
@ -4719,6 +4737,15 @@ _PyType_FromMetaclass_impl(
goto finally;
}
}
if (strcmp(memb->name, "__weaklistoffset__") == 0) {
weaklistoffset_member = memb;
}
if (strcmp(memb->name, "__dictoffset__") == 0) {
dictoffset_member = memb;
}
if (strcmp(memb->name, "__vectorcalloffset__") == 0) {
vectorcalloffset_member = memb;
}
}
break;
case Py_tp_doc:
@ -4882,6 +4909,24 @@ _PyType_FromMetaclass_impl(
Py_ssize_t itemsize = spec->itemsize;
/* Compute special offsets */
Py_ssize_t weaklistoffset = 0;
if (special_offset_from_member(weaklistoffset_member, type_data_offset,
&weaklistoffset) < 0) {
goto finally;
}
Py_ssize_t dictoffset = 0;
if (special_offset_from_member(dictoffset_member, type_data_offset,
&dictoffset) < 0) {
goto finally;
}
Py_ssize_t vectorcalloffset = 0;
if (special_offset_from_member(vectorcalloffset_member, type_data_offset,
&vectorcalloffset) < 0) {
goto finally;
}
/* Allocate the new type
*
* Between here and PyType_Ready, we should limit: