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GeezerVison is showing github.com — GH-142591: Tachyon does not handle non-existent file/module by savannahostrowski · Pull Request #142592 · python/cpython

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@savannahostrowski

@savannahostrowski savannahostrowski commented Dec 11, 2025 •
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This validates script/module/PID exists before starting the profiler. If the target doesn't exist, we now fail fast with a clear error instead of launching an empty TUI.

Screenshot 2025-12-11 at 11 00 21 AM Screenshot 2025-12-11 at 11 00 09 AM
  • Issue: Tachyon does not handle non-existent file/module #142591

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savannahostrowski added 2 commits December 11, 2025 09:58
@savannahostrowski
Fix file does not exist
b3b6fff
@savannahostrowski
Handle module
00ef823
@savannahostrowski
savannahostrowski requested a review from pablogsal December 11, 2025 18:20
@bedevere-app bedevere-app Bot mentioned this pull request Dec 11, 2025
Tachyon does not handle non-existent file/module #142591
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@bedevere-app bedevere-app Bot added the awaiting core review label Dec 11, 2025
@savannahostrowski

savannahostrowski commented Dec 11, 2025

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Hmm, there's a better fix here. Please hold :D
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@savannahostrowski
Fail fast
2ee9bf9
savannahostrowski
savannahostrowski commented Dec 11, 2025
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Comment thread Lib/profiling/sampling/_sync_coordinator.py Resolved

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@savannahostrowski
Merge branch 'main' into tachyon-file-does-not-exist
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@savannahostrowski savannahostrowski added the skip news label Dec 12, 2025
@savannahostrowski savannahostrowski mentioned this pull request Dec 12, 2025
Implement PEP 799 – A dedicated profiling package for organizing Python profiling tools #138122
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Merge branch 'main' into tachyon-file-does-not-exist
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pablogsal
pablogsal reviewed Dec 14, 2025
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Comment thread Lib/profiling/sampling/cli.py Outdated
"""Handle live mode for an existing process."""
# Check if process exists
try:
os.kill(pid, 0)

@pablogsal pablogsal Dec 14, 2025

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I am not sure this works on windows. On Windows, os.kill() only supports signals SIGTERM, CTRL_C_EVENT, and CTRL_BREAK_EVENT. Signal 0 (which is the Unix idiom for checking if a process exists without sending a signal) is not supported on Windows.

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@pablogsal pablogsal Dec 14, 2025

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This also has a TOCTOU problem: the process may die after you check and before we attach

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@pablogsal pablogsal Dec 14, 2025

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The fix probably needs to be done more on the line of https://github.com/python/cpython/pull/142655/changes (we should handle this there)

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@pablogsal

pablogsal commented Dec 14, 2025 •
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I've made some improvements to the implementation.

  • Refactored the sync waiting logic by extracting _check_process_died() and _wait_for_ready_signal() helper functions for better readability. Replaced select.select with selectors.DefaultSelector which has a nicer interface.

  • Changed stderr to always be captured so we can show clean error messages. Added try/except around _run_with_sync() calls to convert RuntimeError to clean sys.exit() messages so non-existent scripts/modules now show clean errors without tracebacks:

  • Also fixed absolute path validation which was incorrectly prepending cwd to absolute paths.
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@pablogsal
pablogsal force-pushed the tachyon-file-does-not-exist branch 3 times, most recently from fe664f9 to 980b035 Compare December 14, 2025 03:16
@pablogsal
fixup! Merge branch 'main' into tachyon-file-does-not-exist
24086c8
@pablogsal
pablogsal force-pushed the tachyon-file-does-not-exist branch from 980b035 to 24086c8 Compare December 14, 2025 03:40
@pablogsal pablogsal mentioned this pull request Dec 14, 2025
gh-142654: show the clear error message when sampling on an unknown PID #142655
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pablogsal approved these changes Dec 14, 2025
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LGTM

Thanks a lot for the PR @savannahostrowski ❤️

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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting core review labels Dec 14, 2025
@pablogsal
pablogsal merged commit f893e8f into python:main Dec 14, 2025
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@bedevere-app bedevere-app Bot removed the awaiting merge label Dec 14, 2025
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@pablogsal pablogsal pablogsal approved these changes

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@savannahostrowski @pablogsal
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