Fix SystemError buffer overflow on Python 3.14+ and add Python 3.14 support#1123
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olzhasar-reef merged 8 commits intoBackblaze:masterfrom Dec 3, 2025
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…upport This commit addresses issue Backblaze#1119 where B2 CLI crashes with SystemError on Python 3.14+ due to a buffer overflow bug in the rst2ansi dependency. Changes: - Add try-except handler in arg_parser.py to catch SystemError from rst2ansi - Fall back to plain text formatting when rst2ansi fails - Add integration test to verify the fix works with real PTY on Python 3.14 - Add dedicated nox session (integration_pty) for PTY tests without xdist - Add Python 3.14 to noxfile.py, CI matrix, and pyproject.toml The root cause is in rst2ansi's get_terminal_size() which passes a 4-byte buffer to TIOCGWINSZ ioctl instead of the required 8 bytes. Python 3.14 enforces stricter buffer validation, triggering the error. Fixes Backblaze#1119
The PTY test doesn't work properly with pytest-xdist parallelization. Instead of a dedicated nox session, run it directly in CI on Python 3.14 without xdist to properly test the buffer overflow fix.
The condition needs to be wrapped in ${{ }} for proper evaluation.
The test_help_with_tty test works correctly with pytest-xdist in CI, so we don't need a separate step. Updated docstring to note that local execution may not trigger the bug due to environment differences.
Move pexpect wrapper with improved error messages from test_autocomplete to shared helpers module, and use it in test_help PTY test.
Python 3.14+ emits multiprocessing resource_tracker warnings about leaked semaphores during test subprocess cleanup. These warnings appear in stderr and cause test assertions to fail. Filter them out the same way we already filter DeprecationWarnings. Fixes integration test failures on Python 3.14.
olzhasar-reef
approved these changes
Dec 3, 2025
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Problem
Fixes #1119 - B2 CLI crashes with
SystemError: buffer overflowon Python 3.14+ due to a bug in therst2ansidependency.The issue occurs because rst2ansi passes a 4-byte buffer to the
TIOCGWINSZioctl call, which expects 8 bytes on most platforms. Python 3.14 enforces stricter buffer validation, causing the crash.Solution
b2/_internal/arg_parser.pyto catch SystemError and fall back to plain text formattingTest Plan
test_help_with_ttythat reproduces the issue on Python 3.14Upstream Fix
Also submitted upstream fix to rst2ansi: Snaipe/python-rst2ansi#20
The fallback can be removed once rst2ansi is updated.
Submitted from reef-technologies fork after internal review