Update docs for -Clink-dead-code to discourage its use
#135561
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r? @Noratrieb rustbot has assigned @Noratrieb. Use |
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I think the change here is pretty uncontroversial, the discouragement is not particularly strong and the other changes are just factually correct. The flag's description has been wrong for many years. r? saethlin |
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…iaskrgr Rollup of 7 pull requests Successful merges: - rust-lang#134754 (Implement `use` associated items of traits) - rust-lang#135481 (coverage: Completely overhaul counter assignment, using node-flow graphs) - rust-lang#135504 (Allow coercing safe-to-call target_feature functions to safe fn pointers) - rust-lang#135561 (Update docs for `-Clink-dead-code` to discourage its use) - rust-lang#135574 (ci: mirror ubuntu:22.04 to ghcr.io) - rust-lang#135585 (resolve symlinks of LLVM tool binaries before copying them) - rust-lang#135588 (Add license-metadata.json to rustc-src tarball.) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#135561 - Zalathar:link-dead-code, r=saethlin Update docs for `-Clink-dead-code` to discourage its use The `-Clink-dead-code` flag was originally added way back in rust-lang#31368, apparently to help improve the output of some older forms of code coverage measurement, and also to address some use-cases for wanting to suppress linker flags like `-dead_strip` and `--gc-section`. In the past it might have also been useful in conjunction with `-Cinstrument-coverage`, but subsequent improvements to coverage instrumentation have made it unnecessary there. [It is also currently used by cargo-fuzz by default](rust-fuzz/cargo-fuzz#391), for reasons that are possibly no longer relevant. --- The flag currently does more than its name suggests, affecting not just linker flags, but also monomorphization decisions. It has also contributed to ICEs (e.g. rust-lang#135515) that would not have occurred without link-dead-code. --- For now, this PR just updates the documentation to be more realistic about what the flag does, and when it should be used (approximately never). In the future, it might be worth looking into properly deprecating this flag, and perhaps making it a no-op if feasible.
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The
-Clink-dead-codeflag was originally added way back in #31368, apparently to help improve the output of some older forms of code coverage measurement, and also to address some use-cases for wanting to suppress linker flags like-dead_stripand--gc-section.In the past it might have also been useful in conjunction with
-Cinstrument-coverage, but subsequent improvements to coverage instrumentation have made it unnecessary there.It is also currently used by cargo-fuzz by default, for reasons that are possibly no longer relevant.
The flag currently does more than its name suggests, affecting not just linker flags, but also monomorphization decisions. It has also contributed to ICEs (e.g. #135515) that would not have occurred without link-dead-code.
For now, this PR just updates the documentation to be more realistic about what the flag does, and when it should be used (approximately never). In the future, it might be worth looking into properly deprecating this flag, and perhaps making it a no-op if feasible.