Fix SystemError buffer overflow on Python 3.14+ and add Python 3.14 support (#351)

* Fix SystemError buffer overflow on Python 3.14+ and add Python 3.14 support

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

* Run PTY test directly in CI without xdist, remove dedicated nox session

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.

* Fix CI condition syntax for PTY test

The condition needs to be wrapped in ${{ }} for proper evaluation.

* Remove separate PTY CI step - regular integration tests catch the bug

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.

* Use skipif decorator directly, consistent with repo pattern

* Simplify test docstring

* Extract patched_spawn to test/helpers.py for reuse

Move pexpect wrapper with improved error messages from test_autocomplete
to shared helpers module, and use it in test_help PTY test.

* Filter resource_tracker warnings in integration tests

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.

Author: przadka

.github/workflows/ci.yml

@@ -86,7 +86,7 @@ jobs:
       fail-fast: false
       matrix:
         os: ["ubuntu-latest", "ubuntu-24.04-arm", "macos-latest", "windows-latest"]
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13", "pypy3.9", "pypy3.10"]
+        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13", "3.14", "pypy3.9", "pypy3.10"]
         exclude:
           - os: "macos-latest"
             python-version: "pypy3.10"
@@ -118,7 +118,7 @@ jobs:
         run: nox -vs integration -p ${{ matrix.python-version }} -- -m "not require_secrets"
       - name: Run integration tests (with secrets)
         # Limit CI workload by running integration tests with secrets only on edge Python versions.
-        if: ${{ env.B2_TEST_APPLICATION_KEY != '' && env.B2_TEST_APPLICATION_KEY_ID != '' && contains(fromJSON('["3.8", "pypy3.10", "3.13"]'), matrix.python-version) }}
+        if: ${{ env.B2_TEST_APPLICATION_KEY != '' && env.B2_TEST_APPLICATION_KEY_ID != '' && contains(fromJSON('["3.8", "pypy3.10", "3.14"]'), matrix.python-version) }}
         run: nox -vs integration -p ${{ matrix.python-version }} -- -m "require_secrets" --cleanup
   test-docker:
     timeout-minutes: 90

b2/_internal/arg_parser.py

@@ -130,7 +130,14 @@ def _encode_description(self, value: str):
             return textwrap.dedent(value)
         else:
             encoding = self._get_encoding()
-            return rst2ansi(value.encode(encoding), output_encoding=encoding)
+            try:
+                return rst2ansi(value.encode(encoding), output_encoding=encoding)
+            except SystemError:
+                # FALLBACK(PARSER): rst2ansi can raise SystemError on Python 3.14+ due to
+                # buffer overflow bug in get_terminal_size ioctl call.
+                # See: https://github.com/Backblaze/B2_Command_Line_Tool/issues/1119
+                # TODO-REMOVE-BY: When rst2ansi is updated or replaced
+                return textwrap.dedent(value)
 
     def _make_short_description(self, usage: str, raw_description: str) -> str:
         if usage:

changelog.d/+python-3.14-support.infrastructure.md

@@ -0,0 +1 @@
+Added Python 3.14 support to CI/CD pipeline and test matrix.

changelog.d/1119.fixed.md

@@ -0,0 +1 @@
+Fixed SystemError buffer overflow crash on Python 3.14+ caused by rst2ansi's terminal size detection bug. The CLI now gracefully handles this error and continues to function normally.

noxfile.py

@@ -42,6 +42,7 @@
         '3.11',
         '3.12',
         '3.13',
+        '3.14',
     ]
     if NOX_PYTHONS is None
     else NOX_PYTHONS.split(',')

pyproject.toml

@@ -21,6 +21,7 @@ classifiers = [
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
+    "Programming Language :: Python :: 3.14",
 ]
 dependencies = [
     "argcomplete>=3.5.2,<4",

test/helpers.py

@@ -8,7 +8,9 @@
 #
 ######################################################################
 import platform
+import sys
 
+import pexpect
 import pytest
 
 _MISSING = object()
@@ -21,6 +23,40 @@ def skip_on_windows(*args, reason='Not supported on Windows', **kwargs):
     )(*args, **kwargs)
 
 
+def patched_spawn(*args, **kwargs):
+    """
+    Wrapper around pexpect.spawn with improved error messages.
+
+    pexpect's errors are confusing to interpret when things go wrong,
+    because it doesn't output the actual stdout by default. This wrapper
+    addresses that inconvenience.
+    """
+    instance = pexpect.spawn(*args, **kwargs)
+
+    def _patch_expect(func):
+        def _wrapper(pattern_list, **kwargs):
+            try:
+                return func(pattern_list, **kwargs)
+            except pexpect.exceptions.TIMEOUT as exc:
+                raise pexpect.exceptions.TIMEOUT(
+                    f'Timeout reached waiting for `{pattern_list}`'
+                ) from exc
+            except pexpect.exceptions.EOF as exc:
+                raise pexpect.exceptions.EOF(f'Received EOF waiting for `{pattern_list}`') from exc
+            except Exception as exc:
+                raise RuntimeError(f'Unexpected error waiting for `{pattern_list}`') from exc
+
+        return _wrapper
+
+    instance.expect = _patch_expect(instance.expect)
+    instance.expect_exact = _patch_expect(instance.expect_exact)
+
+    # capture child shell's output for debugging
+    instance.logfile = sys.stdout.buffer
+
+    return instance
+
+
 def b2_uri_args_v3(bucket_name, path=_MISSING):
     if path is _MISSING:
         return [bucket_name]

test/integration/helpers.py

@@ -368,7 +368,15 @@ def print_json_indented(value):
 
 
 def remove_warnings(text):
-    return linesep.join(line for line in text.split(linesep) if 'DeprecationWarning' not in line)
+    """Filter out Python warnings from command output."""
+    return linesep.join(
+        line
+        for line in text.split(linesep)
+        if 'DeprecationWarning' not in line
+        and 'resource_tracker' not in line  # Python 3.14+ multiprocessing warnings
+        and 'UserWarning' not in line  # Python 3.14+ shows more warning details
+        and 'warnings.warn(' not in line  # Python 3.14+ shows source line in warnings
+    )
 
 
 class StringReader:

test/integration/test_autocomplete.py

@@ -13,7 +13,7 @@
 import pexpect
 import pytest
 
-from test.helpers import skip_on_windows
+from test.helpers import patched_spawn, skip_on_windows
 
 TIMEOUT = 120  # CI can be slow at times when parallelization is extreme
 
@@ -27,41 +27,6 @@
 """
 
 
-def patched_spawn(*args, **kwargs):
-    """
-    Patch pexpect.spawn to improve error messages
-    """
-
-    instance = pexpect.spawn(*args, **kwargs)
-
-    def _patch_expect(func):
-        def _wrapper(pattern_list, **kwargs):
-            try:
-                return func(pattern_list, **kwargs)
-            except pexpect.exceptions.TIMEOUT as exc:
-                raise pexpect.exceptions.TIMEOUT(
-                    f'Timeout reached waiting for `{pattern_list}` to be autocompleted'
-                ) from exc
-            except pexpect.exceptions.EOF as exc:
-                raise pexpect.exceptions.EOF(
-                    f'Received EOF waiting for `{pattern_list}` to be autocompleted'
-                ) from exc
-            except Exception as exc:
-                raise RuntimeError(
-                    f'Unexpected error waiting for `{pattern_list}` to be autocompleted'
-                ) from exc
-
-        return _wrapper
-
-    instance.expect = _patch_expect(instance.expect)
-    instance.expect_exact = _patch_expect(instance.expect_exact)
-
-    # capture child shell's output for debugging
-    instance.logfile = sys.stdout.buffer
-
-    return instance
-
-
 @pytest.fixture(scope='session')
 def bashrc(homedir):
     bashrc_path = homedir / '.bashrc'

test/integration/test_help.py

@@ -7,10 +7,16 @@
 # License https://www.backblaze.com/using_b2_code.html
 #
 ######################################################################
+import os
 import platform
 import re
 import subprocess
 
+import pexpect
+import pytest
+
+from test.helpers import patched_spawn
+
 
 def test_help(cli_version):
     p = subprocess.run(
@@ -26,3 +32,54 @@ def test_help(cli_version):
         expected_name += '.exe'
     assert re.match(r'^_?b2(v\d+)?(\.exe)?$', expected_name)  # test sanity check
     assert f'{expected_name} <command> --help' in p.stdout
+
+
+@pytest.mark.skipif(
+    platform.system() == 'Windows',
+    reason='PTY tests require Unix-like system',
+)
+def test_help_with_tty(cli_version):
+    """
+    Test that B2 CLI --help works correctly with a real PTY.
+
+    Verifies fix for rst2ansi buffer overflow on Python 3.14+.
+    See: https://github.com/Backblaze/B2_Command_Line_Tool/issues/1119
+
+    NOTE: Works in CI with pytest-xdist, but may not trigger the bug locally.
+    """
+    # Set up environment - remove LINES/COLUMNS to ensure ioctl is called
+    env = os.environ.copy()
+    env.pop('LINES', None)
+    env.pop('COLUMNS', None)
+
+    # Spawn b2 --help with pexpect to create a real PTY
+    # This is where the bug would trigger on Python 3.14 without our fix
+    child = patched_spawn(
+        cli_version,
+        ['--help'],
+        env=env,
+        timeout=10,
+    )
+
+    # Wait for process to complete
+    child.expect(pexpect.EOF)
+
+    # Get the output
+    output = child.before.decode('utf-8', errors='replace')
+
+    # Check exit status
+    child.close()
+    exit_code = child.exitstatus
+
+    # Verify the command succeeded and produced help output
+    assert exit_code == 0, (
+        f'b2 --help failed with exit code {exit_code}.\n'
+        f'This may indicate the buffer overflow bug is not properly handled.\n'
+        f'Output: {output}\n'
+        f'See: https://github.com/Backblaze/B2_Command_Line_Tool/issues/1119'
+    )
+
+    # Verify help output contains expected content
+    assert (
+        'b2 <command>' in output or cli_version in output
+    ), f'Help output does not contain expected content.\nOutput: {output}'