gh-135763: Argument Clinic: Impl allow_negative for ssize_t

Author: wiomoc

Include/internal/pycore_abstract.h

@@ -51,6 +51,10 @@ extern int _PyObject_RealIsSubclass(PyObject *derived, PyObject *cls);
 // Export for '_bisect' shared extension.
 PyAPI_FUNC(int) _Py_convert_optional_to_ssize_t(PyObject *, void *);
 
+// Convert Python int to Py_ssize_t. Do nothing if the argument is None.
+// Raises ValueError if argument is negative
+PyAPI_FUNC(int) _Py_convert_optional_to_non_negative_ssize_t(PyObject *, void *);
+
 // Same as PyNumber_Index() but can return an instance of a subclass of int.
 // Export for 'math' shared extension.
 PyAPI_FUNC(PyObject*) _PyNumber_Index(PyObject *o);

Lib/test/clinic.test.c

@@ -1612,12 +1612,14 @@ test_Py_ssize_t_converter
     a: Py_ssize_t = 12
     b: Py_ssize_t(accept={int}) = 34
     c: Py_ssize_t(accept={int, NoneType}) = 56
+    d: Py_ssize_t(accept={int}, allow_negative=False) = 78
+    e: Py_ssize_t(accept={int, NoneType}, allow_negative=False) = 90
     /
 
 [clinic start generated code]*/
 
 PyDoc_STRVAR(test_Py_ssize_t_converter__doc__,
-"test_Py_ssize_t_converter($module, a=12, b=34, c=56, /)\n"
+"test_Py_ssize_t_converter($module, a=12, b=34, c=56, d=78, e=90, /)\n"
 "--\n"
 "\n");
 
@@ -1626,7 +1628,7 @@ PyDoc_STRVAR(test_Py_ssize_t_converter__doc__,
 
 static PyObject *
 test_Py_ssize_t_converter_impl(PyObject *module, Py_ssize_t a, Py_ssize_t b,
-                               Py_ssize_t c);
+                               Py_ssize_t c, Py_ssize_t d, Py_ssize_t e);
 
 static PyObject *
 test_Py_ssize_t_converter(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
@@ -1635,8 +1637,10 @@ test_Py_ssize_t_converter(PyObject *module, PyObject *const *args, Py_ssize_t na
     Py_ssize_t a = 12;
     Py_ssize_t b = 34;
     Py_ssize_t c = 56;
+    Py_ssize_t d = 78;
+    Py_ssize_t e = 90;
 
-    if (!_PyArg_CheckPositional("test_Py_ssize_t_converter", nargs, 0, 3)) {
+    if (!_PyArg_CheckPositional("test_Py_ssize_t_converter", nargs, 0, 5)) {
         goto exit;
     }
     if (nargs < 1) {
@@ -1675,17 +1679,43 @@ test_Py_ssize_t_converter(PyObject *module, PyObject *const *args, Py_ssize_t na
     if (!_Py_convert_optional_to_ssize_t(args[2], &c)) {
         goto exit;
     }
+    if (nargs < 4) {
+        goto skip_optional;
+    }
+    {
+        Py_ssize_t ival = -1;
+        PyObject *iobj = _PyNumber_Index(args[3]);
+        if (iobj != NULL) {
+            ival = PyLong_AsSsize_t(iobj);
+            Py_DECREF(iobj);
+        }
+        if (ival == -1 && PyErr_Occurred()) {
+            goto exit;
+        }
+        d = ival;
+        if (d < 0) {
+            PyErr_SetString(PyExc_ValueError,
+                            "d must not be negative");
+            goto exit;
+        }
+    }
+    if (nargs < 5) {
+        goto skip_optional;
+    }
+    if (!_Py_convert_optional_to_non_negative_ssize_t(args[4], &e)) {
+        goto exit;
+    }
 skip_optional:
-    return_value = test_Py_ssize_t_converter_impl(module, a, b, c);
+    return_value = test_Py_ssize_t_converter_impl(module, a, b, c, d, e);
 
 exit:
     return return_value;
 }
 
 static PyObject *
 test_Py_ssize_t_converter_impl(PyObject *module, Py_ssize_t a, Py_ssize_t b,
-                               Py_ssize_t c)
-/*[clinic end generated code: output=48214bc3d01f4dd7 input=3855f184bb3f299d]*/
+                               Py_ssize_t c, Py_ssize_t d, Py_ssize_t e)
+/*[clinic end generated code: output=df3873c05e53e497 input=5c693ea198fa3dd5]*/
 
 
 /*[clinic input]

Misc/NEWS.d/next/Library/2025-08-26-09-07-02.gh-issue-135763.DVpGUB.rst

@@ -0,0 +1,2 @@
+Add ``allow_negative`` flag to ``Py_ssize_t`` Argument Clinic converter, to
+enable generation of bound checking

Modules/_ctypes/_ctypes.c

@@ -859,7 +859,7 @@ _ctypes.CDataType.from_buffer as CDataType_from_buffer
     type: self
     cls: defining_class
     obj: object
-    offset: Py_ssize_t = 0
+    offset: Py_ssize_t(allow_negative=False) = 0
     /
 
 C.from_buffer(object, offset=0) -> C instance
@@ -870,7 +870,7 @@ Create a C instance from a writeable buffer.
 static PyObject *
 CDataType_from_buffer_impl(PyObject *type, PyTypeObject *cls, PyObject *obj,
                            Py_ssize_t offset)
-/*[clinic end generated code: output=57604e99635abd31 input=0f36cedd105ca28d]*/
+/*[clinic end generated code: output=57604e99635abd31 input=8f43e6bc44373180]*/
 {
     PyObject *mv;
     PyObject *result;
@@ -906,13 +906,6 @@ CDataType_from_buffer_impl(PyObject *type, PyTypeObject *cls, PyObject *obj,
         return NULL;
     }
 
-    if (offset < 0) {
-        PyErr_SetString(PyExc_ValueError,
-                        "offset cannot be negative");
-        Py_DECREF(mv);
-        return NULL;
-    }
-
     if (info->size > buffer->len - offset) {
         PyErr_Format(PyExc_ValueError,
                      "Buffer size too small "
@@ -955,7 +948,7 @@ _ctypes.CDataType.from_buffer_copy as CDataType_from_buffer_copy
     type: self
     cls: defining_class
     buffer: Py_buffer
-    offset: Py_ssize_t = 0
+    offset: Py_ssize_t(allow_negative=False) = 0
     /
 
 C.from_buffer_copy(object, offset=0) -> C instance
@@ -966,7 +959,7 @@ Create a C instance from a readable buffer.
 static PyObject *
 CDataType_from_buffer_copy_impl(PyObject *type, PyTypeObject *cls,
                                 Py_buffer *buffer, Py_ssize_t offset)
-/*[clinic end generated code: output=c8fc62b03e5cc6fa input=2a81e11b765a6253]*/
+/*[clinic end generated code: output=c8fc62b03e5cc6fa input=41f97f512295ceec]*/
 {
     PyObject *result;
 
@@ -980,12 +973,6 @@ CDataType_from_buffer_copy_impl(PyObject *type, PyTypeObject *cls,
         return NULL;
     }
 
-    if (offset < 0) {
-        PyErr_SetString(PyExc_ValueError,
-                        "offset cannot be negative");
-        return NULL;
-    }
-
     if (info->size > buffer->len - offset) {
         PyErr_Format(PyExc_ValueError,
                      "Buffer size too small (%zd instead of at least %zd bytes)",

Modules/_ctypes/callproc.c

@@ -1874,14 +1874,14 @@ My_Py_DECREF(PyObject *self, PyObject *arg)
 @critical_section obj
 _ctypes.resize
     obj: object(subclass_of="clinic_state()->PyCData_Type", type="CDataObject *")
-    size: Py_ssize_t
+    size: Py_ssize_t(allow_negative=False)
     /
 
 [clinic start generated code]*/
 
 static PyObject *
 _ctypes_resize_impl(PyObject *module, CDataObject *obj, Py_ssize_t size)
-/*[clinic end generated code: output=11c89c7dbdbcd53f input=bf5a6aaea8514261]*/
+/*[clinic end generated code: output=11c89c7dbdbcd53f input=1c986b76598bf0eb]*/
 {
     ctypes_state *st = get_module_state(module);
     StgInfo *info;

Modules/_ctypes/clinic/_ctypes.c.h

@@ -1017,23 +1017,18 @@ static PyType_Spec HASHobject_type_spec = {
 /*[clinic input]
 _hashlib.HASHXOF.digest
 
-  length: Py_ssize_t
+  length: Py_ssize_t(allow_negative=False)
 
 Return the digest value as a bytes object.
 [clinic start generated code]*/
 
 static PyObject *
 _hashlib_HASHXOF_digest_impl(HASHobject *self, Py_ssize_t length)
-/*[clinic end generated code: output=dcb09335dd2fe908 input=3eb034ce03c55b21]*/
+/*[clinic end generated code: output=dcb09335dd2fe908 input=224d047da2c12a42]*/
 {
     EVP_MD_CTX *temp_ctx;
     PyObject *retval;
 
-    if (length < 0) {
-        PyErr_SetString(PyExc_ValueError, "negative digest length");
-        return NULL;
-    }
-
     if (length == 0) {
         return Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
     }
@@ -1072,24 +1067,19 @@ _hashlib_HASHXOF_digest_impl(HASHobject *self, Py_ssize_t length)
 /*[clinic input]
 _hashlib.HASHXOF.hexdigest
 
-    length: Py_ssize_t
+    length: Py_ssize_t(allow_negative=False)
 
 Return the digest value as a string of hexadecimal digits.
 [clinic start generated code]*/
 
 static PyObject *
 _hashlib_HASHXOF_hexdigest_impl(HASHobject *self, Py_ssize_t length)
-/*[clinic end generated code: output=519431cafa014f39 input=0e58f7238adb7ab8]*/
+/*[clinic end generated code: output=519431cafa014f39 input=4a41b8ab5d3bfee2]*/
 {
     unsigned char *digest;
     EVP_MD_CTX *temp_ctx;
     PyObject *retval;
 
-    if (length < 0) {
-        PyErr_SetString(PyExc_ValueError, "negative digest length");
-        return NULL;
-    }
-
     if (length == 0) {
         return Py_GetConstant(Py_CONSTANT_EMPTY_STR);
     }

Modules/_ctypes/clinic/callproc.c.h

@@ -1526,7 +1526,7 @@ array.array.fromfile
 
     cls: defining_class
     f: object
-    n: Py_ssize_t
+    n: Py_ssize_t(allow_negative=False)
     /
 
 Read n objects from the file object f and append them to the end of the array.
@@ -1535,17 +1535,13 @@ Read n objects from the file object f and append them to the end of the array.
 static PyObject *
 array_array_fromfile_impl(arrayobject *self, PyTypeObject *cls, PyObject *f,
                           Py_ssize_t n)
-/*[clinic end generated code: output=83a667080b345ebc input=b2b4bdfb7ad4d4ae]*/
+/*[clinic end generated code: output=83a667080b345ebc input=db46b06ac1b6de87]*/
 {
     PyObject *b, *res;
     Py_ssize_t itemsize = self->ob_descr->itemsize;
     Py_ssize_t nbytes;
     int not_enough_bytes;
 
-    if (n < 0) {
-        PyErr_SetString(PyExc_ValueError, "negative count");
-        return NULL;
-    }
     if (n > PY_SSIZE_T_MAX / itemsize) {
         PyErr_NoMemory();
         return NULL;