appender: fix max_files integer underflow when set to zero
#3348
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hds
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Nov 19, 2025
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Thanks for your change! It's a good idea, I think we should document the special meaning of 0 in the function docs.
| pub fn max_log_files(self, n: usize) -> Self { | ||
| Self { | ||
| max_files: Some(n), | ||
| max_files: Some(n).filter(|&n| n > 0), |
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We should also add a comment stating that setting n to 0 will disable the max files (effectively make it infinite).
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Thanks for your feedback! I've updated the documentation and added comment to the line.
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max_files integer underflow when set to zeromax_files integer underflow when set to zero
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Nov 25, 2025
# 0.2.4 (November 30, 2025) ### Added - Prune old files at startup ([#2966]) - Add fallback to file creation date ([#3000]) ### Fixed - Fix `max_files` integer underflow when set to zero ([#3348]) ### Documented - Update tracing-appender docs link to correct docs.rs URL ([#3325]) [#2966]: https://github.com/tokio-rs/tracing/pull/#2966 [#3000]: https://github.com/tokio-rs/tracing/pull/#3000 [#3325]: https://github.com/tokio-rs/tracing/pull/#3325 [#3348]: https://github.com/tokio-rs/tracing/pull/#3348
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Nov 26, 2025
# 0.2.4 (November 30, 2025) ### Added - Prune old files at startup ([#2966]) - Add fallback to file creation date ([#3000]) - Introduce weekly rotation ([#3218]) ### Fixed - Fix `max_files` integer underflow when set to zero ([#3348]) ### Documented - Update tracing-appender docs link to correct docs.rs URL ([#3325]) [#2966]: https://github.com/tokio-rs/tracing/pull/#2966 [#3000]: https://github.com/tokio-rs/tracing/pull/#3000 [#3218]: https://github.com/tokio-rs/tracing/pull/#3218 [#3325]: https://github.com/tokio-rs/tracing/pull/#3325 [#3348]: https://github.com/tokio-rs/tracing/pull/#3348
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# 0.2.4 (November 26, 2025) ### Added - Prune old files at startup ([#2966]) - Add fallback to file creation date ([#3000]) - Introduce weekly rotation ([#3218]) ### Fixed - Fix `max_files` integer underflow when set to zero ([#3348]) ### Documented - Update tracing-appender docs link to correct docs.rs URL ([#3325]) [#2966]: https://github.com/tokio-rs/tracing/pull/#2966 [#3000]: https://github.com/tokio-rs/tracing/pull/#3000 [#3218]: https://github.com/tokio-rs/tracing/pull/#3218 [#3325]: https://github.com/tokio-rs/tracing/pull/#3325 [#3348]: https://github.com/tokio-rs/tracing/pull/#3348 # Please enter the commit message for your changes. Lines starting # with '#' will be kept; you may remove them yourself if you want to. # An empty message aborts the commit. # # Date: Tue Nov 25 12:06:02 2025 +0100 # # On branch hds/tracing-appender-0.2.4 # Your branch is up to date with 'origin/hds/tracing-appender-0.2.4'. # # Changes to be committed: # modified: tracing-appender/CHANGELOG.md # modified: tracing-appender/Cargo.toml # modified: tracing-appender/README.md # # Untracked files: # backport-2025-01.txt # backport-2025-05.txt # backup-Cargo.lock # commit-msg # dingxiangfei-patch2.diff # justfile # tracing_subscriber.d #
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# 0.2.4 (November 26, 2025) ### Added - Prune old files at startup ([#2966]) - Add fallback to file creation date ([#3000]) - Introduce weekly rotation ([#3218]) ### Fixed - Fix `max_files` integer underflow when set to zero ([#3348]) ### Documented - Update tracing-appender docs link to correct docs.rs URL ([#3325]) [#2966]: https://github.com/tokio-rs/tracing/pull/#2966 [#3000]: https://github.com/tokio-rs/tracing/pull/#3000 [#3218]: https://github.com/tokio-rs/tracing/pull/#3218 [#3325]: https://github.com/tokio-rs/tracing/pull/#3325 [#3348]: https://github.com/tokio-rs/tracing/pull/#3348
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Motivation
When
max_filesset to zero, rolling.rs:695 will cause integer underflow and panicking in debug build. In my opinion the API should prevent this from happening as "zero" is a validusizevalue to pass in.Solution
Currently, in release builds, if
max_filesis set to zero, it behaves just likeu64::MAXonx86_64platforms. Therefore, I decided to simply makezero == None, which should align with the existing behavior but without the panicking. I believe this can be considered as "non-breaking".Feel free to advise if there a more preferred way of fixing this. Any help on how to provide tests would also be appreciated!