bpo-40584: Update PyType_FromModuleAndSpec() to process tp_vectorcall_offset (GH-20026)

1 files changed, 12 insertions, 2 deletions

diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 525f5ac..a36b4dc 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -2954,10 +2954,10 @@ PyType_FromModuleAndSpec(PyObject *module, PyType_Spec *spec, PyObject *bases)
     PyTypeObject *type, *base;
 
     const PyType_Slot *slot;
-    Py_ssize_t nmembers, weaklistoffset, dictoffset;
+    Py_ssize_t nmembers, weaklistoffset, dictoffset, vectorcalloffset;
     char *res_start;
 
-    nmembers = weaklistoffset = dictoffset = 0;
+    nmembers = weaklistoffset = dictoffset = vectorcalloffset = 0;
     for (slot = spec->slots; slot->slot; slot++) {
         if (slot->slot == Py_tp_members) {
             nmembers = 0;
@@ -2975,6 +2975,12 @@ PyType_FromModuleAndSpec(PyObject *module, PyType_Spec *spec, PyObject *bases)
                     assert(memb->flags == READONLY);
                     dictoffset = memb->offset;
                 }
+                if (strcmp(memb->name, "__vectorcalloffset__") == 0) {
+                    // The PyMemberDef must be a Py_ssize_t and readonly
+                    assert(memb->type == T_PYSSIZET);
+                    assert(memb->flags == READONLY);
+                    vectorcalloffset = memb->offset;
+                }
             }
         }
     }
@@ -3123,6 +3129,10 @@ PyType_FromModuleAndSpec(PyObject *module, PyType_Spec *spec, PyObject *bases)
         type->tp_dealloc = subtype_dealloc;
     }
 
+    if (vectorcalloffset) {
+        type->tp_vectorcall_offset = vectorcalloffset;
+    }
+
     if (PyType_Ready(type) < 0)
         goto fail;