From 81dc8b12f08f64da756b5d0de5592e60740ba02c Mon Sep 17 00:00:00 2001
From: Dino Viehland <dinoviehland@meta.com>
Date: Wed, 8 Oct 2025 09:13:34 -0700
Subject: [PATCH] [3.14] gh-139525: Don't specialize functions which have a
 modified vectorcall (GH-139524) (#139709)

Don't specialize functions which have a modified vectorcall
---
 Lib/test/test_opcache.py    |  8 ++++++++
 Modules/_testinternalcapi.c | 20 ++++++++++++++++++++
 Python/specialize.c         |  9 +++++++++
 3 files changed, 37 insertions(+)

diff --git a/Lib/test/test_opcache.py b/Lib/test/test_opcache.py
index a45aafc63fa6..2e50c1c62b32 100644
--- a/Lib/test/test_opcache.py
+++ b/Lib/test/test_opcache.py
@@ -567,6 +567,14 @@ class TestCallCache(TestBase):
         with self.assertRaises(RecursionError):
             test()
 
+    def test_dont_specialize_custom_vectorcall(self):
+        def f():
+            raise Exception("no way")
+
+        _testinternalcapi.set_vectorcall_nop(f)
+        for _ in range(_testinternalcapi.SPECIALIZATION_THRESHOLD):
+            f()
+
 
 def make_deferred_ref_count_obj():
     """Create an object that uses deferred reference counting.
diff --git a/Modules/_testinternalcapi.c b/Modules/_testinternalcapi.c
index afb72d3df832..5d877b5655b8 100644
--- a/Modules/_testinternalcapi.c
+++ b/Modules/_testinternalcapi.c
@@ -2389,6 +2389,25 @@ emscripten_set_up_async_input_device(PyObject *self, PyObject *Py_UNUSED(ignored
 }
 #endif
 
+static PyObject *
+vectorcall_nop(PyObject *callable, PyObject *const *args,
+               size_t nargsf, PyObject *kwnames)
+{
+    Py_RETURN_NONE;
+}
+
+static PyObject *
+set_vectorcall_nop(PyObject *self, PyObject *func)
+{
+    if (!PyFunction_Check(func)) {
+        PyErr_SetString(PyExc_TypeError, "expected function");
+        return NULL;
+    }
+
+    ((PyFunctionObject*)func)->vectorcall = vectorcall_nop;
+    Py_RETURN_NONE;
+}
+
 static PyMethodDef module_functions[] = {
     {"get_configs", get_configs, METH_NOARGS},
     {"get_recursion_depth", get_recursion_depth, METH_NOARGS},
@@ -2496,6 +2515,7 @@ static PyMethodDef module_functions[] = {
 #ifdef __EMSCRIPTEN__
     {"emscripten_set_up_async_input_device", emscripten_set_up_async_input_device, METH_NOARGS},
 #endif
+    {"set_vectorcall_nop", set_vectorcall_nop, METH_O},
     {NULL, NULL} /* sentinel */
 };
 
diff --git a/Python/specialize.c b/Python/specialize.c
index dd00f1cb6b00..4ba854d2ae8c 100644
--- a/Python/specialize.c
+++ b/Python/specialize.c
@@ -630,6 +630,7 @@ _PyCode_Quicken(_Py_CODEUNIT *instructions, Py_ssize_t size, int enable_counters
 #define SPEC_FAIL_CALL_INIT_NOT_PYTHON 21
 #define SPEC_FAIL_CALL_PEP_523 22
 #define SPEC_FAIL_CALL_BOUND_METHOD 23
+#define SPEC_FAIL_CALL_VECTORCALL 24
 #define SPEC_FAIL_CALL_CLASS_MUTABLE 26
 #define SPEC_FAIL_CALL_METHOD_WRAPPER 28
 #define SPEC_FAIL_CALL_OPERATOR_WRAPPER 29
@@ -2071,6 +2072,10 @@ specialize_py_call(PyFunctionObject *func, _Py_CODEUNIT *instr, int nargs,
         SPECIALIZATION_FAIL(CALL, SPEC_FAIL_CALL_PEP_523);
         return -1;
     }
+    if (func->vectorcall != _PyFunction_Vectorcall) {
+        SPECIALIZATION_FAIL(CALL, SPEC_FAIL_CALL_VECTORCALL);
+        return -1;
+    }
     int argcount = -1;
     if (kind == SPEC_FAIL_CODE_NOT_OPTIMIZED) {
         SPECIALIZATION_FAIL(CALL, SPEC_FAIL_CODE_NOT_OPTIMIZED);
@@ -2110,6 +2115,10 @@ specialize_py_call_kw(PyFunctionObject *func, _Py_CODEUNIT *instr, int nargs,
         SPECIALIZATION_FAIL(CALL, SPEC_FAIL_CALL_PEP_523);
         return -1;
     }
+    if (func->vectorcall != _PyFunction_Vectorcall) {
+        SPECIALIZATION_FAIL(CALL, SPEC_FAIL_CALL_VECTORCALL);
+        return -1;
+    }
     if (kind == SPEC_FAIL_CODE_NOT_OPTIMIZED) {
         SPECIALIZATION_FAIL(CALL, SPEC_FAIL_CODE_NOT_OPTIMIZED);
         return -1;
-- 
2.47.3