5405b29570
Fixes the following security issue: - CVE-2021-3177: Python 3.x through 3.9.1 has a buffer overflow in PyCArg_repr in _ctypes/callproc.c, which may lead to remote code execution in certain Python applications that accept floating-point numbers as untrusted input, as demonstrated by a 1e300 argument to c_double.from_param. This occurs because sprintf is used unsafely. For details, see the advisory: https://python-security.readthedocs.io/vuln/ctypes-buffer-overflow-pycarg_repr.html Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
191 lines
7.3 KiB
Diff
191 lines
7.3 KiB
Diff
From c347cbe694743cee120457aa6626712f7799a932 Mon Sep 17 00:00:00 2001
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From: "Miss Islington (bot)"
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<31488909+miss-islington@users.noreply.github.com>
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Date: Mon, 18 Jan 2021 13:29:31 -0800
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Subject: [PATCH] closes bpo-42938: Replace snprintf with Python unicode
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formatting in ctypes param reprs. (GH-24247)
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(cherry picked from commit 916610ef90a0d0761f08747f7b0905541f0977c7)
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Co-authored-by: Benjamin Peterson <benjamin@python.org>
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Co-authored-by: Benjamin Peterson <benjamin@python.org>
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Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
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---
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Lib/ctypes/test/test_parameters.py | 43 ++++++++++++++++
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.../2021-01-18-09-27-31.bpo-42938.4Zn4Mp.rst | 2 +
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Modules/_ctypes/callproc.c | 51 +++++++------------
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3 files changed, 64 insertions(+), 32 deletions(-)
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create mode 100644 Misc/NEWS.d/next/Security/2021-01-18-09-27-31.bpo-42938.4Zn4Mp.rst
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diff --git a/Lib/ctypes/test/test_parameters.py b/Lib/ctypes/test/test_parameters.py
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index e4c25fd880..531894fdec 100644
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--- a/Lib/ctypes/test/test_parameters.py
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+++ b/Lib/ctypes/test/test_parameters.py
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@@ -201,6 +201,49 @@ class SimpleTypesTestCase(unittest.TestCase):
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with self.assertRaises(ZeroDivisionError):
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WorseStruct().__setstate__({}, b'foo')
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+ def test_parameter_repr(self):
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+ from ctypes import (
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+ c_bool,
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+ c_char,
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+ c_wchar,
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+ c_byte,
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+ c_ubyte,
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+ c_short,
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+ c_ushort,
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+ c_int,
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+ c_uint,
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+ c_long,
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+ c_ulong,
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+ c_longlong,
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+ c_ulonglong,
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+ c_float,
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+ c_double,
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+ c_longdouble,
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+ c_char_p,
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+ c_wchar_p,
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+ c_void_p,
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+ )
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+ self.assertRegex(repr(c_bool.from_param(True)), r"^<cparam '\?' at 0x[A-Fa-f0-9]+>$")
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+ self.assertEqual(repr(c_char.from_param(97)), "<cparam 'c' ('a')>")
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+ self.assertRegex(repr(c_wchar.from_param('a')), r"^<cparam 'u' at 0x[A-Fa-f0-9]+>$")
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+ self.assertEqual(repr(c_byte.from_param(98)), "<cparam 'b' (98)>")
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+ self.assertEqual(repr(c_ubyte.from_param(98)), "<cparam 'B' (98)>")
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+ self.assertEqual(repr(c_short.from_param(511)), "<cparam 'h' (511)>")
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+ self.assertEqual(repr(c_ushort.from_param(511)), "<cparam 'H' (511)>")
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+ self.assertRegex(repr(c_int.from_param(20000)), r"^<cparam '[li]' \(20000\)>$")
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+ self.assertRegex(repr(c_uint.from_param(20000)), r"^<cparam '[LI]' \(20000\)>$")
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+ self.assertRegex(repr(c_long.from_param(20000)), r"^<cparam '[li]' \(20000\)>$")
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+ self.assertRegex(repr(c_ulong.from_param(20000)), r"^<cparam '[LI]' \(20000\)>$")
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+ self.assertRegex(repr(c_longlong.from_param(20000)), r"^<cparam '[liq]' \(20000\)>$")
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+ self.assertRegex(repr(c_ulonglong.from_param(20000)), r"^<cparam '[LIQ]' \(20000\)>$")
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+ self.assertEqual(repr(c_float.from_param(1.5)), "<cparam 'f' (1.5)>")
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+ self.assertEqual(repr(c_double.from_param(1.5)), "<cparam 'd' (1.5)>")
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+ self.assertEqual(repr(c_double.from_param(1e300)), "<cparam 'd' (1e+300)>")
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+ self.assertRegex(repr(c_longdouble.from_param(1.5)), r"^<cparam ('d' \(1.5\)|'g' at 0x[A-Fa-f0-9]+)>$")
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+ self.assertRegex(repr(c_char_p.from_param(b'hihi')), "^<cparam 'z' \(0x[A-Fa-f0-9]+\)>$")
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+ self.assertRegex(repr(c_wchar_p.from_param('hihi')), "^<cparam 'Z' \(0x[A-Fa-f0-9]+\)>$")
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+ self.assertRegex(repr(c_void_p.from_param(0x12)), r"^<cparam 'P' \(0x0*12\)>$")
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+
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################################################################
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if __name__ == '__main__':
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diff --git a/Misc/NEWS.d/next/Security/2021-01-18-09-27-31.bpo-42938.4Zn4Mp.rst b/Misc/NEWS.d/next/Security/2021-01-18-09-27-31.bpo-42938.4Zn4Mp.rst
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new file mode 100644
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index 0000000000..7df65a156f
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--- /dev/null
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+++ b/Misc/NEWS.d/next/Security/2021-01-18-09-27-31.bpo-42938.4Zn4Mp.rst
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@@ -0,0 +1,2 @@
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+Avoid static buffers when computing the repr of :class:`ctypes.c_double` and
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+:class:`ctypes.c_longdouble` values.
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diff --git a/Modules/_ctypes/callproc.c b/Modules/_ctypes/callproc.c
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index b0a36a3024..f2506de544 100644
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--- a/Modules/_ctypes/callproc.c
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+++ b/Modules/_ctypes/callproc.c
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@@ -489,58 +489,47 @@ is_literal_char(unsigned char c)
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static PyObject *
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PyCArg_repr(PyCArgObject *self)
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{
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- char buffer[256];
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switch(self->tag) {
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case 'b':
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case 'B':
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- sprintf(buffer, "<cparam '%c' (%d)>",
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+ return PyUnicode_FromFormat("<cparam '%c' (%d)>",
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self->tag, self->value.b);
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- break;
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case 'h':
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case 'H':
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- sprintf(buffer, "<cparam '%c' (%d)>",
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+ return PyUnicode_FromFormat("<cparam '%c' (%d)>",
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self->tag, self->value.h);
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- break;
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case 'i':
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case 'I':
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- sprintf(buffer, "<cparam '%c' (%d)>",
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+ return PyUnicode_FromFormat("<cparam '%c' (%d)>",
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self->tag, self->value.i);
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- break;
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case 'l':
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case 'L':
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- sprintf(buffer, "<cparam '%c' (%ld)>",
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+ return PyUnicode_FromFormat("<cparam '%c' (%ld)>",
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self->tag, self->value.l);
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- break;
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case 'q':
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case 'Q':
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- sprintf(buffer,
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-#ifdef MS_WIN32
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- "<cparam '%c' (%I64d)>",
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-#else
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- "<cparam '%c' (%lld)>",
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-#endif
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+ return PyUnicode_FromFormat("<cparam '%c' (%lld)>",
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self->tag, self->value.q);
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- break;
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case 'd':
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- sprintf(buffer, "<cparam '%c' (%f)>",
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- self->tag, self->value.d);
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- break;
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- case 'f':
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- sprintf(buffer, "<cparam '%c' (%f)>",
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- self->tag, self->value.f);
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- break;
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-
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+ case 'f': {
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+ PyObject *f = PyFloat_FromDouble((self->tag == 'f') ? self->value.f : self->value.d);
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+ if (f == NULL) {
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+ return NULL;
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+ }
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+ PyObject *result = PyUnicode_FromFormat("<cparam '%c' (%R)>", self->tag, f);
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+ Py_DECREF(f);
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+ return result;
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+ }
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case 'c':
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if (is_literal_char((unsigned char)self->value.c)) {
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- sprintf(buffer, "<cparam '%c' ('%c')>",
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+ return PyUnicode_FromFormat("<cparam '%c' ('%c')>",
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self->tag, self->value.c);
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}
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else {
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- sprintf(buffer, "<cparam '%c' ('\\x%02x')>",
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+ return PyUnicode_FromFormat("<cparam '%c' ('\\x%02x')>",
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self->tag, (unsigned char)self->value.c);
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}
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- break;
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/* Hm, are these 'z' and 'Z' codes useful at all?
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Shouldn't they be replaced by the functionality of c_string
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@@ -549,22 +538,20 @@ PyCArg_repr(PyCArgObject *self)
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case 'z':
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case 'Z':
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case 'P':
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- sprintf(buffer, "<cparam '%c' (%p)>",
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+ return PyUnicode_FromFormat("<cparam '%c' (%p)>",
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self->tag, self->value.p);
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break;
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default:
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if (is_literal_char((unsigned char)self->tag)) {
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- sprintf(buffer, "<cparam '%c' at %p>",
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+ return PyUnicode_FromFormat("<cparam '%c' at %p>",
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(unsigned char)self->tag, (void *)self);
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}
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else {
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- sprintf(buffer, "<cparam 0x%02x at %p>",
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+ return PyUnicode_FromFormat("<cparam 0x%02x at %p>",
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(unsigned char)self->tag, (void *)self);
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}
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- break;
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}
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- return PyUnicode_FromString(buffer);
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}
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static PyMemberDef PyCArgType_members[] = {
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--
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2.20.1
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