Fix SystemError buffer overflow on Python 3.14+ and add Python 3.14 support #351
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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
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I've also submitted a PR to fix this at the source in rst2ansi: Snaipe/python-rst2ansi#20 This defensive fix in B2 CLI protects users immediately, while the upstream PR will help the broader ecosystem once merged. |
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.
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The PR looks great overall.
However, the Integration tests seem to fail on Python3.14 with an ambiguous error:
FAILED test/integration/test_b2_command_line.py::test_header_arguments - AssertionError: Unexpected stderr line: "/opt/hostedtoolcache/Python/3.14.0/arm64/lib/python3.14/multiprocessing/resource_tracker.py:297: UserWarning: resource_tracker: There appear to be 1 leaked semaphore objects to clean up at shutdown: {'/mp-84uu7hqr'}"
I re-ran the workflow to see if those are flaky, and it looks like the failure persisted:
https://github.com/reef-technologies/B2_Command_Line_Tool/actions/runs/19671931302/job/56830215284?pr=351
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olzhasar-reef
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Dec 2, 2025
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.
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Fixes Backblaze#1119 - B2 CLI crashes with
SystemError: buffer overflowon Python 3.14+.Problem
Python 3.14 enforces stricter buffer validation. The
rst2ansidependency passes a 4-byte buffer toTIOCGWINSZioctl, which expects 8 bytes. This crashes the CLI on Python 3.14 (affects macOS Homebrew users).Solution
arg_parser.pyto catch SystemError and fall back to plain textTesting
Upstream issue: Snaipe/python-rst2ansi#18