bytearray.resize() must not clear the object on error (memory allocation failure) #157242

Python 3.15 reimplemented bytearray using an internal bytes object (to implement the bytearray.take_bytes() method). _PyBytes_Resize() is used internally to resize the bytearray object. Problem: if _PyBytes_Resize() fails, the bytearray object is cleared.

On Python 3.14, the bytearray is not cleared on resize failure.

The following example works on Python 3.14 but fails on Python 3.15.

import _testcapi

data = b'some data'
ba = bytearray(data)
try:
    try:
        _testcapi.set_nomemory(0)
        ba.resize(1024)
    except MemoryError:
        pass
    else:
        raise AssertionError("expect MemoryError")
finally:
    _testcapi.remove_mem_hooks()
if ba != data:
    raise AssertionError(f"{ba} != {data}")

Linked PRs

• gh-157242: Fix PyBytesWriter_Resize() on MemoryError #157243
• gh-157242: Leave bytearray unchanged if resize() fails #157340
• gh-157242: Do not close io.BytesIO on MemoryError #157344
• gh-157242: Fix test_capi on Py_TRACE_REFS build #157350
• gh-157242: Fix set_nomemory() on Py_TRACE_REFS build #157351
• gh-157242: Add more PyBytesWriter tests #157352
• gh-157242: Add _PyBytes_IsMutable() assertion #157371
• gh-157242: Allow negative grow in PyBytesWriter_Grow() #157375
• gh-157242: Add support.inject_memory_error() function #157431
• gh-157242: Fix typo in _PyBytes_Resize() #157619
• gh-157242: Add byteswriter_check_consistency() #157723
• gh-157242: Use support.inject_memory_error_cm() in tests #157811
• [3.15] gh-157242: Fix PyBytesWriter_Resize() on MemoryError (#157243) #159260
• [3.15] gh-157242: Leave bytearray unchanged if resize() fails (#157340) #159274
• [3.15] gh-157242: Do not close io.BytesIO on MemoryError (GH-157344) #159275
• [3.15] gh-157242: Fix set_nomemory() on Py_TRACE_REFS build (#157351) #159292
• [3.14] gh-157242: Fix set_nomemory() on Py_TRACE_REFS build (#157351) #159528
• [3.14] gh-157242: Do not close io.BytesIO on MemoryError #159529
• gh-157242: Use support.inject_memory_error_cm() in test_dict #159543
• [3.15] gh-157242: Add more PyBytesWriter tests #159546
• [3.15] gh-157242: Add support.inject_memory_error() function #159553
• [3.14] gh-157242: Add support.inject_memory_error() function #159582