https://github.com/python/cpython/commit/2894aa14f22430e9b6d4676afead6da7c79... commit: 2894aa14f22430e9b6d4676afead6da7c79209ca branch: main author: Steve Dower <steve.dower@python.org> committer: zooba <steve.dower@microsoft.com> date: 2024-06-28T16:26:21+01:00 summary: gh-121115: Skip __index__ in PyLong_AsNativeBytes by default (GH-121118) files: A Misc/NEWS.d/next/Core and Builtins/2024-06-28-10-02-58.gh-issue-121115.EeSLfc.rst M Doc/c-api/long.rst M Include/cpython/longobject.h M Lib/test/test_capi/test_long.py M Objects/longobject.c diff --git a/Doc/c-api/long.rst b/Doc/c-api/long.rst index a0e111af5996d7..42162914c0aec8 100644 --- a/Doc/c-api/long.rst +++ b/Doc/c-api/long.rst @@ -405,14 +405,13 @@ distinguished from a number. Use :c:func:`PyErr_Occurred` to disambiguate. Passing zero to *n_bytes* will return the size of a buffer that would be large enough to hold the value. This may be larger than technically - necessary, but not unreasonably so. + necessary, but not unreasonably so. If *n_bytes=0*, *buffer* may be + ``NULL``. .. note:: Passing *n_bytes=0* to this function is not an accurate way to determine - the bit length of a value. - - If *n_bytes=0*, *buffer* may be ``NULL``. + the bit length of the value. To get at the entire Python value of an unknown size, the function can be called twice: first to determine the buffer size, then to fill it:: @@ -462,6 +461,7 @@ distinguished from a number. Use :c:func:`PyErr_Occurred` to disambiguate. .. c:macro:: Py_ASNATIVEBYTES_NATIVE_ENDIAN ``3`` .. c:macro:: Py_ASNATIVEBYTES_UNSIGNED_BUFFER ``4`` .. c:macro:: Py_ASNATIVEBYTES_REJECT_NEGATIVE ``8`` + .. c:macro:: Py_ASNATIVEBYTES_ALLOW_INDEX ``16`` ============================================= ====== Specifying ``Py_ASNATIVEBYTES_NATIVE_ENDIAN`` will override any other endian @@ -483,6 +483,13 @@ distinguished from a number. Use :c:func:`PyErr_Occurred` to disambiguate. provided there is enough space for at least one sign bit, regardless of whether ``Py_ASNATIVEBYTES_UNSIGNED_BUFFER`` was specified. + If ``Py_ASNATIVEBYTES_ALLOW_INDEX`` is specified and a non-integer value is + passed, its :meth:`~object.__index__` method will be called first. This may + result in Python code executing and other threads being allowed to run, which + could cause changes to other objects or values in use. When *flags* is + ``-1``, this option is not set, and non-integer values will raise + :exc:`TypeError`. + .. note:: With the default *flags* (``-1``, or *UNSIGNED_BUFFER* without diff --git a/Include/cpython/longobject.h b/Include/cpython/longobject.h index 19a6722d07734a..e7e0c3d9764f20 100644 --- a/Include/cpython/longobject.h +++ b/Include/cpython/longobject.h @@ -10,6 +10,7 @@ PyAPI_FUNC(PyObject*) PyLong_FromUnicodeObject(PyObject *u, int base); #define Py_ASNATIVEBYTES_NATIVE_ENDIAN 3 #define Py_ASNATIVEBYTES_UNSIGNED_BUFFER 4 #define Py_ASNATIVEBYTES_REJECT_NEGATIVE 8 +#define Py_ASNATIVEBYTES_ALLOW_INDEX 16 /* PyLong_AsNativeBytes: Copy the integer value to a native variable. buffer points to the first byte of the variable. @@ -20,8 +21,10 @@ PyAPI_FUNC(PyObject*) PyLong_FromUnicodeObject(PyObject *u, int base); * 2 - native endian * 4 - unsigned destination (e.g. don't reject copying 255 into one byte) * 8 - raise an exception for negative inputs - If flags is -1 (all bits set), native endian is used and value truncation - behaves most like C (allows negative inputs and allow MSB set). + * 16 - call __index__ on non-int types + If flags is -1 (all bits set), native endian is used, value truncation + behaves most like C (allows negative inputs and allow MSB set), and non-int + objects will raise a TypeError. Big endian mode will write the most significant byte into the address directly referenced by buffer; little endian will write the least significant byte into that address. diff --git a/Lib/test/test_capi/test_long.py b/Lib/test/test_capi/test_long.py index 06a29b5a0505b4..7e8d571ae234d1 100644 --- a/Lib/test/test_capi/test_long.py +++ b/Lib/test/test_capi/test_long.py @@ -496,8 +496,9 @@ def test_long_asnativebytes(self): "PyLong_AsNativeBytes(v, <unknown>, 0, -1)") self.assertEqual(buffer, b"\x5a", "buffer overwritten when it should not have been") - # Also check via the __index__ path - self.assertEqual(expect, asnativebytes(Index(v), buffer, 0, -1), + # Also check via the __index__ path. + # We pass Py_ASNATIVEBYTES_NATIVE_ENDIAN | ALLOW_INDEX + self.assertEqual(expect, asnativebytes(Index(v), buffer, 0, 3 | 16), "PyLong_AsNativeBytes(Index(v), <unknown>, 0, -1)") self.assertEqual(buffer, b"\x5a", "buffer overwritten when it should not have been") @@ -607,6 +608,12 @@ def test_long_asnativebytes(self): with self.assertRaises(ValueError): asnativebytes(-1, buffer, 0, 8) + # Ensure omitting Py_ASNATIVEBYTES_ALLOW_INDEX raises on __index__ value + with self.assertRaises(TypeError): + asnativebytes(Index(1), buffer, 0, -1) + with self.assertRaises(TypeError): + asnativebytes(Index(1), buffer, 0, 3) + # Check a few error conditions. These are validated in code, but are # unspecified in docs, so if we make changes to the implementation, it's # fine to just update these tests rather than preserve the behaviour. diff --git a/Misc/NEWS.d/next/Core and Builtins/2024-06-28-10-02-58.gh-issue-121115.EeSLfc.rst b/Misc/NEWS.d/next/Core and Builtins/2024-06-28-10-02-58.gh-issue-121115.EeSLfc.rst new file mode 100644 index 00000000000000..aaecc873551cc7 --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2024-06-28-10-02-58.gh-issue-121115.EeSLfc.rst @@ -0,0 +1,3 @@ +:c:func:`PyLong_AsNativeBytes` no longer uses :meth:`~object.__index__` +methods by default. The ``Py_ASNATIVEBYTES_ALLOW_INDEX`` flag has been added +to allow it. diff --git a/Objects/longobject.c b/Objects/longobject.c index 86afec9a414134..4ca259fb08e8c7 100644 --- a/Objects/longobject.c +++ b/Objects/longobject.c @@ -1128,13 +1128,17 @@ PyLong_AsNativeBytes(PyObject* vv, void* buffer, Py_ssize_t n, int flags) if (PyLong_Check(vv)) { v = (PyLongObject *)vv; } - else { + else if (flags != -1 && (flags & Py_ASNATIVEBYTES_ALLOW_INDEX)) { v = (PyLongObject *)_PyNumber_Index(vv); if (v == NULL) { return -1; } do_decref = 1; } + else { + PyErr_Format(PyExc_TypeError, "expect int, got %T", vv); + return -1; + } if ((flags != -1 && (flags & Py_ASNATIVEBYTES_REJECT_NEGATIVE)) && _PyLong_IsNegative(v)) {