https://github.com/python/cpython/commit/adc11271c117802ad1751c0cfbac131d68d0c156
commit: adc11271c117802ad1751c0cfbac131d68d0c156
branch: 3.15
author: Victor Stinner <[email protected]>
committer: vstinner <[email protected]>
date: 2026-10-16T16:18:33Z
summary:
[3.15] gh-157710: Add MemoryError tests to PyUnicodeWriter (#159548)
* gh-157710: Add _PyUnicodeWriter_CanWrite() function (#157712)
Make sure that a writer can be modified before writing into it.
* Document that PyUnicodeWriter is not thread safe.
* Add singletons tests to test_capi.test_unicode.
* Check PyUnicode_CheckExact() earlier in _PyUnicode_IsModifiable().
(cherry picked from commit 854295809ad5a42c9461f34d47b1252a3b4a2027)
* gh-157710: Add MemoryError tests to PyUnicodeWriter (#157853)
Add a test changing the buffer kind multiple times.
Add assertions to _PyUnicodeWriter_InitWithBuffer().
(cherry picked from commit 6b974528366e5452300c1f3de27f5062b1160039)
* No need to export _PyUnicode_IsModifiable()
files:
M Doc/c-api/unicode.rst
M Include/internal/pycore_unicodeobject.h
M Lib/test/support/__init__.py
M Lib/test/test_capi/test_unicode.py
M Objects/longobject.c
M Objects/unicode_writer.c
M Objects/unicodeobject.c
diff --git a/Doc/c-api/unicode.rst b/Doc/c-api/unicode.rst
index 268bcffc5dd1d1f..5b3a1b958a7217d 100644
--- a/Doc/c-api/unicode.rst
+++ b/Doc/c-api/unicode.rst
@@ -1826,6 +1826,9 @@ object.
The instance must be destroyed by :c:func:`PyUnicodeWriter_Finish` on
success, or :c:func:`PyUnicodeWriter_Discard` on error.
+ The API is **not thread safe**. To share a writer with multiple threads, a
+ critical section or a lock is needed.
+
.. c:function:: PyUnicodeWriter* PyUnicodeWriter_Create(Py_ssize_t length)
Create a Unicode writer instance.
diff --git a/Include/internal/pycore_unicodeobject.h
b/Include/internal/pycore_unicodeobject.h
index 74d84052a2bb2be..fcdf75ad50d74c3 100644
--- a/Include/internal/pycore_unicodeobject.h
+++ b/Include/internal/pycore_unicodeobject.h
@@ -104,12 +104,31 @@ _PyUnicode_EnsureUnicode(PyObject *obj)
return 0;
}
+#ifndef NDEBUG
+static inline int
+_PyUnicodeWriter_CanWrite(_PyUnicodeWriter *writer)
+{
+ // Code adapted from _PyUnicode_IsModifiable()
+ assert(!writer->readonly);
+ PyObject *buffer = writer->buffer;
+ assert(buffer != NULL);
+ // Do not use _PyObject_IsUniquelyReferenced(): the caller can have its own
+ // lock to prevent a writer being used by two theads at the same time.
+ assert(Py_REFCNT(buffer) == 1);
+ assert(PyUnstable_Unicode_GET_CACHED_HASH(buffer) == -1);
+ assert(!PyUnicode_CHECK_INTERNED(buffer));
+ assert(!_Py_IsImmortal(buffer));
+ return 1;
+}
+#endif
+
static inline int
_PyUnicodeWriter_WriteCharInline(_PyUnicodeWriter *writer, Py_UCS4 ch)
{
assert(ch <= _Py_MAX_UNICODE);
if (_PyUnicodeWriter_Prepare(writer, 1, ch) < 0)
return -1;
+ assert(_PyUnicodeWriter_CanWrite(writer));
PyUnicode_WRITE(writer->kind, writer->data, writer->pos, ch);
writer->pos++;
return 0;
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index cbfbac23aafdbbe..4d09bd7573d0e69 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -3453,3 +3453,22 @@ def built_with_c_assertions():
return Py_DEBUG
else:
return bool(_testlimitedcapi._py_getbuiltwithassert())
+
+
[email protected]
+def inject_memory_error_cm(start=0, stop=0):
+ """
+ Similar to inject_memory_error() but can be used as a context manager.
+
+ Raise SkipTest if the _testcapi extension module is missing
+ """
+ try:
+ import _testcapi
+ except ImportError:
+ raise unittest.SkipTest("_testcapi required")
+
+ try:
+ _testcapi.set_nomemory(start, stop)
+ yield
+ finally:
+ _testcapi.remove_mem_hooks()
diff --git a/Lib/test/test_capi/test_unicode.py
b/Lib/test/test_capi/test_unicode.py
index 06c13dcfe75720c..30549863cd04fde 100644
--- a/Lib/test/test_capi/test_unicode.py
+++ b/Lib/test/test_capi/test_unicode.py
@@ -2101,10 +2101,8 @@ def test_substring_empty(self):
self.assertEqual(writer.finish(), '')
def test_singletons(self):
- for size in (0, 123):
- with self.subTest(size=size):
- writer = self.create_writer(size)
- self.assertIs(writer.finish(), '')
+ writer = self.create_writer(5)
+ self.assertIs(writer.finish(), '')
for ch in range(256):
with self.subTest(ch=ch):
@@ -2113,6 +2111,39 @@ def test_singletons(self):
writer.write_substring(ch + 'xxx', 0, 1)
self.assertIs(writer.finish(), ch)
+ @support.nomemtest
+ def test_memory_error(self):
+ # Inject MemoryError in PyUnicodeWriter_WriteStr()
+ writer = self.create_writer(0)
+ writer.write_str("start")
+ with self.assertRaises(MemoryError):
+ with support.inject_memory_error_cm():
+ # Resize the internal str object
+ writer.write_str("s" * 1024)
+ writer.write_str(" end")
+ self.assertEqual(writer.finish(), "start end")
+
+ # Inject MemoryError in PyUnicodeWriter_Finish()
+ writer = self.create_writer(1024)
+ writer.write_str("abc")
+ with self.assertRaises(MemoryError):
+ with support.inject_memory_error_cm():
+ # Need to truncate the internal str object
+ writer.finish()
+
+ def test_change_kind(self):
+ writer = self.create_writer(0)
+ # Create an ASCII buffer
+ writer.write_str('ascii ')
+ # Change the buffer to UCS1
+ writer.write_str('latin1:\xe9 ')
+ # Change the buffer to UCS2
+ writer.write_str('ucs2:\u20ac ')
+ # Change the buffer to UCS4
+ writer.write_str('ucs4:\U0010ffff')
+ self.assertEqual(writer.finish(),
+ 'ascii latin1:\xe9 ucs2:\u20ac ucs4:\U0010ffff')
+
# Test PyUnicodeWriter_Format()
@unittest.skipIf(ctypes is None, 'need ctypes')
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 6454565aebf6a11..ec4368b87a247d9 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -2220,6 +2220,7 @@ long_to_decimal_string_internal(PyObject *aa,
Py_DECREF(scratch);
return -1;
}
+ assert(_PyUnicodeWriter_CanWrite(writer));
}
else if (bytes_writer) {
*bytes_str = PyBytesWriter_GrowAndUpdatePointer(bytes_writer, strlen,
@@ -2390,8 +2391,10 @@ long_format_binary(PyObject *aa, int base, int alternate,
}
if (writer) {
- if (_PyUnicodeWriter_Prepare(writer, sz, 'x') == -1)
+ if (_PyUnicodeWriter_Prepare(writer, sz, 'x') == -1) {
return -1;
+ }
+ assert(_PyUnicodeWriter_CanWrite(writer));
}
else if (bytes_writer) {
*bytes_str = PyBytesWriter_GrowAndUpdatePointer(bytes_writer, sz,
diff --git a/Objects/unicode_writer.c b/Objects/unicode_writer.c
index a753c9b971c702c..58b5d60333a7868 100644
--- a/Objects/unicode_writer.c
+++ b/Objects/unicode_writer.c
@@ -199,10 +199,13 @@ void PyUnicodeWriter_Discard(PyUnicodeWriter *writer)
void
_PyUnicodeWriter_InitWithBuffer(_PyUnicodeWriter *writer, PyObject *buffer)
{
+ assert(PyUnstable_Object_IsUniquelyReferenced(buffer));
+
memset(writer, 0, sizeof(*writer));
writer->buffer = buffer;
_PyUnicodeWriter_Update(writer);
writer->min_length = writer->size;
+ assert(_PyUnicodeWriter_CanWrite(writer));
}
@@ -350,6 +353,8 @@ _PyUnicodeWriter_WriteStr(_PyUnicodeWriter *writer,
PyObject *str)
if (_PyUnicodeWriter_PrepareInternal(writer, len, maxchar) == -1)
return -1;
}
+
+ assert(_PyUnicodeWriter_CanWrite(writer));
_PyUnicode_FastCopyCharacters(writer->buffer, writer->pos,
str, 0, len);
writer->pos += len;
@@ -428,6 +433,7 @@ _PyUnicodeWriter_WriteSubstring(_PyUnicodeWriter *writer,
PyObject *str,
if (_PyUnicodeWriter_Prepare(writer, len, maxchar) < 0) {
return -1;
}
+ assert(_PyUnicodeWriter_CanWrite(writer));
_PyUnicode_FastCopyCharacters(writer->buffer, writer->pos,
str, start, len);
@@ -485,8 +491,10 @@ _PyUnicodeWriter_WriteASCIIString(_PyUnicodeWriter *writer,
return 0;
}
- if (_PyUnicodeWriter_Prepare(writer, len, 127) == -1)
+ if (_PyUnicodeWriter_Prepare(writer, len, 127) == -1) {
return -1;
+ }
+ assert(_PyUnicodeWriter_CanWrite(writer));
switch (writer->kind)
{
@@ -591,6 +599,7 @@ _PyUnicodeWriter_WriteLatin1String(_PyUnicodeWriter *writer,
maxchar = ucs1lib_find_max_char((const Py_UCS1*)str, (const Py_UCS1*)str +
len);
if (_PyUnicodeWriter_Prepare(writer, len, maxchar) == -1)
return -1;
+ assert(_PyUnicodeWriter_CanWrite(writer));
unicode_write_cstr(writer->buffer, writer->pos, str, len);
writer->pos += len;
return 0;
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 8fbe8a714ff7c6a..df7e4e28bbc25ad 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -1743,18 +1743,21 @@ unicode_is_singleton(PyObject *unicode)
}
#endif
+// If this function is updated, update also _PyUnicodeWriter_CanWrite().
int
_PyUnicode_IsModifiable(PyObject *unicode)
{
assert(_PyUnicode_CHECK(unicode));
+ if (!PyUnicode_CheckExact(unicode))
+ return 0;
+ // On Free Threading, this test fails if called from a thread other
+ // than the one which created the str object.
if (!_PyObject_IsUniquelyReferenced(unicode))
return 0;
if (PyUnicode_HASH(unicode) != -1)
return 0;
if (PyUnicode_CHECK_INTERNED(unicode))
return 0;
- if (!PyUnicode_CheckExact(unicode))
- return 0;
#ifdef Py_DEBUG
/* singleton refcount is greater than 1 */
assert(!unicode_is_singleton(unicode));
@@ -2006,6 +2009,7 @@ PyUnicodeWriter_WriteWideChar(PyUnicodeWriter *pub_writer,
if (_PyUnicodeWriter_Prepare(writer, size - num_surrogates, maxchar) < 0) {
return -1;
}
+ assert(_PyUnicodeWriter_CanWrite(writer));
int kind = writer->kind;
void *data = (Py_UCS1*)writer->data + writer->pos * kind;
@@ -2303,6 +2307,7 @@ PyUnicodeWriter_WriteUCS4(PyUnicodeWriter *pub_writer,
if (_PyUnicodeWriter_Prepare(writer, size, maxchar) < 0) {
return -1;
}
+ assert(_PyUnicodeWriter_CanWrite(writer));
int kind = writer->kind;
void *data = (Py_UCS1*)writer->data + writer->pos * kind;
@@ -2589,8 +2594,10 @@ unicode_fromformat_write_str(_PyUnicodeWriter *writer,
PyObject *str,
else
maxchar = writer->maxchar;
- if (_PyUnicodeWriter_Prepare(writer, arglen, maxchar) == -1)
+ if (_PyUnicodeWriter_Prepare(writer, arglen, maxchar) == -1) {
return -1;
+ }
+ assert(_PyUnicodeWriter_CanWrite(writer));
fill = Py_MAX(width - length, 0);
if (fill && !(flags & F_LJUST)) {
@@ -2880,8 +2887,10 @@ unicode_fromformat_arg(_PyUnicodeWriter *writer,
Py_ssize_t spacepad = Py_MAX(width - precision - sign, 0);
Py_ssize_t zeropad = Py_MAX(precision - len, 0);
- if (_PyUnicodeWriter_Prepare(writer, width, 127) == -1)
+ if (_PyUnicodeWriter_Prepare(writer, width, 127) == -1) {
return NULL;
+ }
+ assert(_PyUnicodeWriter_CanWrite(writer));
if (spacepad && !(flags & F_LJUST)) {
if (PyUnicode_Fill(writer->buffer, writer->pos, spacepad, ' ') ==
-1)
@@ -5408,6 +5417,7 @@ _PyUnicode_DecodeUTF8Writer(_PyUnicodeWriter *writer,
if (_PyUnicodeWriter_Prepare(writer, size, 127) < 0) {
return -1;
}
+ assert(_PyUnicodeWriter_CanWrite(writer));
const char *starts = s;
const char *end = s + size;
_______________________________________________
Python-checkins mailing list -- [email protected]
To unsubscribe send an email to [email protected]
https://mail.python.org/mailman3//lists/python-checkins.python.org
Member address: [email protected]
