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gh-155742: Check singletons consistency at Python exit (#157572) · python/cpython@8bcbcf8 · GitHub

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  2. cpython

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vstinner
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encukou
authored
gh-155742: Check singletons consistency at Python exit (#157572)
In debug mode at Python exit, check if immutable singleton objects have been modified by mistake to detect bugs in C extensions. Add tests corrupting bytes, str, bool and int singleton objects. Add pycore_global_objects_fini.h internal header file. pycore_global_objects_fini_generated.h is now fully generated by the script. Co-authored-by: Petr Viktorin <encukou@gmail.com>
1 parent e8c06d6 commit 8bcbcf8

12 files changed

Lines changed: 1231 additions & 2475 deletions

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‎Include/internal/pycore_global_objects_fini.h‎

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#ifndef Py_INTERNAL_GLOBAL_OBJECTS_FINI_H
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#define Py_INTERNAL_GLOBAL_OBJECTS_FINI_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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#ifndef Py_BUILD_CORE
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# error "this header requires Py_BUILD_CORE define"
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#endif
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#ifdef Py_DEBUG
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#include "pycore_bytesobject.h" // _PyBytes_CheckOverflow()
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#include "pycore_long.h" // TAG_FROM_SIGN_AND_SIZE()
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static inline void
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_PyStaticObject_CheckSingleton(PyObject *obj, PyTypeObject *type)
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{
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// Check PyObject.ob_refcnt
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_PyObject_ASSERT(obj, _Py_IsImmortal(obj));
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// Check PyObject.ob_type
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_PyObject_ASSERT(obj, Py_TYPE(obj) == type);
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}
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static void
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_PyStaticObject_CheckLongSingleton(PyObject *obj, long value, int is_bool)
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{
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PyTypeObject *type = is_bool ? &PyBool_Type : &PyLong_Type;
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_PyStaticObject_CheckSingleton(obj, type);
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// Check _PyLong_CompactValue()
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Py_ssize_t compact = _PyLong_CompactValue((const PyLongObject *)obj);
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_PyObject_ASSERT(obj, compact == value);
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// Check tv_tag and ob_digit[0]
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_PyLongValue *long_value = &((PyLongObject*)obj)->long_value;
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int sign = (value == 0) ? 0 : ((value < 0) ? -1 : 1);
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uintptr_t lv_tag = TAG_FROM_SIGN_AND_SIZE(sign, (value == 0) ? 0 : 1);
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if (!is_bool) {
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lv_tag |= IMMORTALITY_BIT_MASK;
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}
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_PyObject_ASSERT(obj, long_value->lv_tag == lv_tag);
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_PyObject_ASSERT(obj, long_value->ob_digit[0] == Py_ABS(value));
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}
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static inline void
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_PyStaticObject_CheckBytesSingleton(PyObject *obj,
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Py_ssize_t size, unsigned char ch)
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{
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_PyStaticObject_CheckSingleton(obj, &PyBytes_Type);
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_PyObject_ASSERT(obj, PyBytes_GET_SIZE(obj) == size);
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const unsigned char *str = (const unsigned char *)PyBytes_AS_STRING(obj);
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_PyObject_ASSERT(obj, str[0] == ch);
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_PyBytes_CheckOverflow(obj, obj, "bytes singleton");
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}
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static void
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_PyStaticObject_CheckUnicode(PyObject *obj, const char *str, Py_ssize_t length)
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{
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_PyStaticObject_CheckSingleton(obj, &PyUnicode_Type);
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_PyObject_ASSERT(obj, _PyUnicode_CheckConsistency(obj, 1));
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_PyObject_ASSERT(obj, PyUnicode_GET_LENGTH(obj) == length);
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_PyObject_ASSERT(obj, PyUnicode_KIND(obj) == PyUnicode_1BYTE_KIND);
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const Py_UCS1 *data = PyUnicode_1BYTE_DATA(obj);
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_PyObject_ASSERT(obj, memcmp(data, str, length) == 0);
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_PyObject_ASSERT(obj, data[length] == 0);
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}
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static void
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_PyStaticObject_CheckUnicodeCharSingleton(PyObject *obj, unsigned char ch)
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{
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_PyStaticObject_CheckUnicode(obj, (char *)&ch, 1);
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_PyObject_ASSERT(obj, PyUnicode_IS_ASCII(obj) == (ch <= 127));
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}
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static void
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_PyStaticObject_CheckUnicodeSingleton(PyObject *obj,
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const char *str, Py_ssize_t length)
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{
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_PyStaticObject_CheckUnicode(obj, str, length);
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_PyObject_ASSERT(obj, PyUnicode_IS_ASCII(obj));
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}
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#endif // Py_DEBUG
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#ifdef __cplusplus
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}
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#endif
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#endif /* !Py_INTERNAL_GLOBAL_OBJECTS_FINI_H */

‎Include/internal/pycore_global_objects_fini_generated.h‎

Lines changed: 912 additions & 2438 deletions
Some generated files are not rendered by default. Learn more about customizing how changed files appear on GitHub.

‎Lib/test/test_capi/test_misc.py‎

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@@ -3094,5 +3094,51 @@ def test_ceval_decref(self):
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self.assertEqual(lines.count("DESTROY list"), 2)
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@unittest.skipUnless(support.Py_DEBUG, 'need Py_DEBUG')
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class TestCheckSingleton(unittest.TestCase):
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# Test that _PyStaticObjects_CheckAll() detects memory corruptions in
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# singleton objects at Python exit.
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def check(self, code):
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code = f"""if 1:
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import _testcapi
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from test import support
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support.SuppressCrashReport().__enter__()
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{code}
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"""
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proc = assert_python_failure("-c", code)
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return proc.err
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def test_corrupt_bytes(self):
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stderr = self.check("_testcapi.corrupt_bytes(b'a', b'#')")
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self.assertIn((b'_PyStaticObject_CheckBytesSingleton: '
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b'Assertion "str[0] == ch" failed'), stderr)
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self.assertIn(b"object repr : b'#'", stderr)
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def test_corrupt_unicode(self):
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stderr = self.check("_testcapi.corrupt_unicode('a', '#')")
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self.assertIn((b'_PyStaticObject_CheckUnicode: '
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b'Assertion "memcmp(data, str, length) == 0" failed'), stderr)
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self.assertIn(b"object repr : '#'", stderr)
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def test_corrupt_bool(self):
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stderr = self.check("_testcapi.corrupt_long(True, 0)")
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self.assertIn((b'_PyStaticObject_CheckLongSingleton: '
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b'Assertion "compact == value" failed'),
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stderr)
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self.assertIn(b"object repr : True", stderr)
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def test_corrupt_long(self):
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stderr = self.check("_testcapi.corrupt_long(5, 42)")
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self.assertIn((b'_PyStaticObject_CheckLongSingleton: '
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b'Assertion "compact == value" failed'),
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stderr)
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self.assertIn(b"object repr : 42", stderr)
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if __name__ == "__main__":
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unittest.main()

‎Makefile.pre.in‎

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@@ -1345,6 +1345,7 @@ PYTHON_HEADERS= \
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$(srcdir)/Include/internal/pycore_getopt.h \
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$(srcdir)/Include/internal/pycore_gil.h \
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$(srcdir)/Include/internal/pycore_global_objects.h \
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$(srcdir)/Include/internal/pycore_global_objects_fini.h \
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$(srcdir)/Include/internal/pycore_global_objects_fini_generated.h \
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$(srcdir)/Include/internal/pycore_global_strings.h \
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$(srcdir)/Include/internal/pycore_hamt.h \

‎Misc/NEWS.d/next/Core_and_Builtins/2026-09-15-17-04-54.gh-issue-155742.2DUW_9.rst‎

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In debug mode at Python exit, check if immutable singleton objects have been
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modified by mistake to detect bugs in C extensions. Patch by Victor Stinner.

‎Modules/_testcapi/bytes.c‎

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@@ -567,6 +567,21 @@ bytearray_overflow(PyObject *Py_UNUSED(module), PyObject *args)
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}
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// Write into an immutable bytes object to test _PyStaticObjects_CheckAll()
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static PyObject *
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corrupt_bytes(PyObject *Py_UNUSED(module), PyObject *args)
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{
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char *bytes, *override;
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Py_ssize_t size;
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if (!PyArg_ParseTuple(args, "yy#", &bytes, &override, &size)) {
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return NULL;
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}
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memcpy(bytes, override, size);
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Py_RETURN_NONE;
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}
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static PyMethodDef test_methods[] = {
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{"bytes_resize", bytes_resize, METH_VARARGS},
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{"bytes_join", bytes_join, METH_VARARGS},
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{"test_byteswriter_ptr", test_byteswriter_ptr, METH_NOARGS},
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{"bytes_overflow", bytes_overflow, METH_VARARGS},
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{"bytearray_overflow", bytearray_overflow, METH_VARARGS},
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{"corrupt_bytes", corrupt_bytes, METH_VARARGS},
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{NULL},
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};
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‎Modules/_testcapi/long.c‎

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@@ -281,6 +281,21 @@ get_pylong_layout(PyObject *module, PyObject *Py_UNUSED(args))
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}
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// Write into an immutable int object to test _PyStaticObjects_CheckAll()
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static PyObject *
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corrupt_long(PyObject *Py_UNUSED(module), PyObject *args)
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{
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PyObject *obj;
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int value;
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if (!PyArg_ParseTuple(args, "Oi", &obj, &value)) {
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return NULL;
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}
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((PyLongObject*)obj)->long_value.ob_digit[0] = value;
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Py_RETURN_NONE;
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}
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static PyMethodDef test_methods[] = {
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_TESTCAPI_CALL_LONG_COMPACT_API_METHODDEF
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{"pylong_fromunicodeobject", pylong_fromunicodeobject, METH_VARARGS},
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{"pylong_ispositive", pylong_ispositive, METH_O},
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{"pylong_isnegative", pylong_isnegative, METH_O},
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{"pylong_iszero", pylong_iszero, METH_O},
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{"corrupt_long", corrupt_long, METH_VARARGS},
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{NULL},
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};
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‎Modules/_testcapi/unicode.c‎

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}
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// Write into an immutable str object to test _PyStaticObjects_CheckAll()
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static PyObject *
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corrupt_unicode(PyObject *Py_UNUSED(module), PyObject *args)
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{
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PyObject *obj, *override;
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if (!PyArg_ParseTuple(args, "OO", &obj, &override)) {
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return NULL;
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}
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assert(PyUnicode_KIND(obj) == PyUnicode_1BYTE_KIND);
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assert(PyUnicode_KIND(override) == PyUnicode_1BYTE_KIND);
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Py_UCS1 *dst = PyUnicode_1BYTE_DATA(obj);
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Py_UCS1 *src = PyUnicode_1BYTE_DATA(override);
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Py_ssize_t size = PyUnicode_GET_LENGTH(override);
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memcpy(dst, src, size);
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Py_RETURN_NONE;
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}
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// --- PyUnicodeWriter type -------------------------------------------------
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typedef struct {
@@ -622,6 +641,7 @@ static PyMethodDef TestMethods[] = {
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{"unicode_copycharacters", unicode_copycharacters, METH_VARARGS},
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{"unicode_GET_CACHED_HASH", unicode_GET_CACHED_HASH, METH_O},
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{"test_py_identifier", test_py_identifier, METH_NOARGS},
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{"corrupt_unicode", corrupt_unicode, METH_VARARGS},
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{NULL},
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};
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‎PCbuild/pythoncore.vcxproj‎

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<ClInclude Include="..\Include\internal\pycore_getopt.h" />
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<ClInclude Include="..\Include\internal\pycore_gil.h" />
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<ClInclude Include="..\Include\internal\pycore_global_objects.h" />
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<ClInclude Include="..\Include\internal\pycore_global_objects_fini.h" />
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<ClInclude Include="..\Include\internal\pycore_global_objects_fini_generated.h" />
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<ClInclude Include="..\Include\internal\pycore_hamt.h" />
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<ClInclude Include="..\Include\internal\pycore_hashtable.h" />

‎PCbuild/pythoncore.vcxproj.filters‎

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<ClInclude Include="..\Include\internal\pycore_global_objects.h">
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<Filter>Include\internal</Filter>
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</ClInclude>
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<ClInclude Include="..\Include\internal\pycore_global_objects_fini.h">
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<Filter>Include\internal</Filter>
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</ClInclude>
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<ClInclude Include="..\Include\internal\pycore_global_objects_fini_generated.h">
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<Filter>Include\internal</Filter>
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</ClInclude>

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