[Python] `MemoryMappedFile().resize()` segfaults when no file has been opened

[marinelay]

Describe the bug, including details regarding any error messages, version, and platform.

Summary

MemoryMappedFile can be directly constructed without opening a file, and resize() on that object terminates the interpreter.
I found this while fuzzing Python C extension modules.
I think this unsupported state should raise a Python exception rather than terminate the process.

Versions

PyArrow 25.0.1, CPython 3.12.3, Debian 12 x86_64, glibc 2.36

Reproducer

import pyarrow as pa

pa.MemoryMappedFile().resize(0)

Segmentation fault (core dumped)

ASan/UBSan result

I built PyArrow 25.0.0 from source with Clang 18 using ASan and UBSan instrumentation.
UBSan reports a member call on a null arrow::io::MemoryMappedFile in the generated wrapper:

build/lib.cpp:252525:86: runtime error:
member call on null pointer of type 'arrow::io::MemoryMappedFile'

    #0 pyarrow.lib.MemoryMappedFile.resize(...)
       build/lib.cpp:252525:86

SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
build/lib.cpp:252525:86

ASan then reports a read from address 0x28 on the same path.
The sanitizer process exits with code 134 after ASan aborts.

Component(s)

Python