Fix tail calls to #[track_caller] functions
#144865
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r? @fee1-dead rustbot has assigned @fee1-dead. Use |
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These commits modify the If this was unintentional then you should revert the changes before this PR is merged. |
This was referenced Aug 3, 2025
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I do not get it, both tests pass for me locally ?_? |
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Update: @jieyouxu figured this out. It looks like the test suite that failed was running with |
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not too familiar with tail calls but the diff looks good to me r? compiler |
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r? lqd maybe (since you were excited about tail calls ^^') |
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It also LGTM -- though to be clear, I'm not familiar with the Also, do we have to involve t-lang for new lints? |
Would this be a silent downgrade? I think that would be a terrible idea, since for me the main usage of |
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@lqd the wording is certainly not ideal, although I'm not entirely sure what would be the proper way to describe this situation. I don't think T-lang needs to be involved, since this lint is triggered only by an unstable/experimental feature (but they'll certainly have to look into the lint before stabilizing the feature). @VorpalBlade it will not be silent, as this PR also adds a lint. However, note that functions marked with |
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Ok I wasn't aware of the procedure for new lints. |
lqd
approved these changes
Aug 7, 2025
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| declare_lint! { | ||
| /// The `tail_call_track_caller` lint detects usage of `become` attempting to tail call | ||
| /// function marked with `#[track_caller]`. |
| /// is no different than a normal call (except for changes in drop order). | ||
| pub TAIL_CALL_TRACK_CALLER, | ||
| Warn, | ||
| "detects tail calls of functions marked with `#[track_caller]`" |
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Could you gate this behind the tail call feature?
I can't remember the syntax but I think it's something like @feature = ....
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I did not know this is something that can be done!
The syntax is apparently @feature_gate = ident;. I've gated the lint.
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🚀 @bors r+ |
Zalathar
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Fix tail calls to `#[track_caller]` functions We want `#[track_caller]` to be semver independent, i.e. it should not be a breaking change to add or remove it. Since it changes ABI of a function (adding an additional argument) we have to be careful to preserve this property when adding tail calls. The only way to achieve this that I can see is: - we forbid tail calls in functions which are marked with `#[track_caller]` (already implemented) - tail-calling a `#[track_caller]` marked function downgrades the tail-call to a normal call (or equivalently tail-calls the shim made by fn def to fn ptr cast) (this pr) Ideally the downgrade would be performed by a MIR pass, but that requires post mono MIR opts (cc `@saethlin,` rust-lang#131650). For now I've changed code in cg_ssa to accomodate this behaviour (+ added a hack to mono collector so that the shim is actually generated) Additionally I added a lint, although I don't think it's strictly necessary. Alternative to rust-lang#144762 (and thus closes rust-lang#144762) Fixes rust-lang#144755
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Rollup of 22 pull requests Successful merges: - #118087 (Add Ref/RefMut try_map method) - #122661 (Change the desugaring of `assert!` for better error output) - #140740 (Add `-Zindirect-branch-cs-prefix`) - #142640 (Implement autodiff using intrinsics) - #143075 (compiler: Allow `extern "interrupt" fn() -> !`) - #144865 (Fix tail calls to `#[track_caller]` functions) - #144944 (E0793: Clarify that it applies to unions as well) - #144947 (Fix description of unsigned `checked_exact_div`) - #145004 (Couple of minor cleanups) - #145005 (strip prefix of temporary file names when it exceeds filesystem name length limit) - #145012 (Tail call diagnostics to include lifetime info) - #145065 (resolve: Introduce `RibKind::Block`) - #145120 (llvm: Accept new LLVM lifetime format) - #145189 (Weekly `cargo update`) - #145235 (Minor `[const]` tweaks) - #145275 (fix(compiler/rustc_codegen_llvm): apply `target-cpu` attribute) - #145322 (Resolve the prelude import in `build_reduced_graph`) - #145331 (Make std use the edition 2024 prelude) - #145369 (Do not ICE on private type in field of unresolved struct) - #145378 (Add `FnContext` in parser for diagnostic) - #145389 ([rustdoc] Revert "rustdoc search: prefer stable items in search results") - #145392 (coverage: Remove intermediate data structures from mapping creation) r? `@ghost` `@rustbot` modify labels: rollup
Zalathar
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Fix tail calls to `#[track_caller]` functions We want `#[track_caller]` to be semver independent, i.e. it should not be a breaking change to add or remove it. Since it changes ABI of a function (adding an additional argument) we have to be careful to preserve this property when adding tail calls. The only way to achieve this that I can see is: - we forbid tail calls in functions which are marked with `#[track_caller]` (already implemented) - tail-calling a `#[track_caller]` marked function downgrades the tail-call to a normal call (or equivalently tail-calls the shim made by fn def to fn ptr cast) (this pr) Ideally the downgrade would be performed by a MIR pass, but that requires post mono MIR opts (cc ``@saethlin,`` rust-lang#131650). For now I've changed code in cg_ssa to accomodate this behaviour (+ added a hack to mono collector so that the shim is actually generated) Additionally I added a lint, although I don't think it's strictly necessary. Alternative to rust-lang#144762 (and thus closes rust-lang#144762) Fixes rust-lang#144755
bors
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Rollup of 21 pull requests Successful merges: - #118087 (Add Ref/RefMut try_map method) - #122661 (Change the desugaring of `assert!` for better error output) - #142640 (Implement autodiff using intrinsics) - #143075 (compiler: Allow `extern "interrupt" fn() -> !`) - #144865 (Fix tail calls to `#[track_caller]` functions) - #144944 (E0793: Clarify that it applies to unions as well) - #144947 (Fix description of unsigned `checked_exact_div`) - #145004 (Couple of minor cleanups) - #145005 (strip prefix of temporary file names when it exceeds filesystem name length limit) - #145012 (Tail call diagnostics to include lifetime info) - #145065 (resolve: Introduce `RibKind::Block`) - #145120 (llvm: Accept new LLVM lifetime format) - #145189 (Weekly `cargo update`) - #145235 (Minor `[const]` tweaks) - #145275 (fix(compiler/rustc_codegen_llvm): apply `target-cpu` attribute) - #145322 (Resolve the prelude import in `build_reduced_graph`) - #145331 (Make std use the edition 2024 prelude) - #145369 (Do not ICE on private type in field of unresolved struct) - #145378 (Add `FnContext` in parser for diagnostic) - #145389 ([rustdoc] Revert "rustdoc search: prefer stable items in search results") - #145392 (coverage: Remove intermediate data structures from mapping creation) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of #144865 - WaffleLapkin:track-tail, r=lqd Fix tail calls to `#[track_caller]` functions We want `#[track_caller]` to be semver independent, i.e. it should not be a breaking change to add or remove it. Since it changes ABI of a function (adding an additional argument) we have to be careful to preserve this property when adding tail calls. The only way to achieve this that I can see is: - we forbid tail calls in functions which are marked with `#[track_caller]` (already implemented) - tail-calling a `#[track_caller]` marked function downgrades the tail-call to a normal call (or equivalently tail-calls the shim made by fn def to fn ptr cast) (this pr) Ideally the downgrade would be performed by a MIR pass, but that requires post mono MIR opts (cc ```@saethlin,``` #131650). For now I've changed code in cg_ssa to accomodate this behaviour (+ added a hack to mono collector so that the shim is actually generated) Additionally I added a lint, although I don't think it's strictly necessary. Alternative to #144762 (and thus closes #144762) Fixes #144755
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Rollup of 21 pull requests Successful merges: - rust-lang/rust#118087 (Add Ref/RefMut try_map method) - rust-lang/rust#122661 (Change the desugaring of `assert!` for better error output) - rust-lang/rust#142640 (Implement autodiff using intrinsics) - rust-lang/rust#143075 (compiler: Allow `extern "interrupt" fn() -> !`) - rust-lang/rust#144865 (Fix tail calls to `#[track_caller]` functions) - rust-lang/rust#144944 (E0793: Clarify that it applies to unions as well) - rust-lang/rust#144947 (Fix description of unsigned `checked_exact_div`) - rust-lang/rust#145004 (Couple of minor cleanups) - rust-lang/rust#145005 (strip prefix of temporary file names when it exceeds filesystem name length limit) - rust-lang/rust#145012 (Tail call diagnostics to include lifetime info) - rust-lang/rust#145065 (resolve: Introduce `RibKind::Block`) - rust-lang/rust#145120 (llvm: Accept new LLVM lifetime format) - rust-lang/rust#145189 (Weekly `cargo update`) - rust-lang/rust#145235 (Minor `[const]` tweaks) - rust-lang/rust#145275 (fix(compiler/rustc_codegen_llvm): apply `target-cpu` attribute) - rust-lang/rust#145322 (Resolve the prelude import in `build_reduced_graph`) - rust-lang/rust#145331 (Make std use the edition 2024 prelude) - rust-lang/rust#145369 (Do not ICE on private type in field of unresolved struct) - rust-lang/rust#145378 (Add `FnContext` in parser for diagnostic) - rust-lang/rust#145389 ([rustdoc] Revert "rustdoc search: prefer stable items in search results") - rust-lang/rust#145392 (coverage: Remove intermediate data structures from mapping creation) r? `@ghost` `@rustbot` modify labels: rollup
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We want
#[track_caller]to be semver independent, i.e. it should not be a breaking change to add or remove it. Since it changes ABI of a function (adding an additional argument) we have to be careful to preserve this property when adding tail calls.The only way to achieve this that I can see is:
#[track_caller](already implemented)#[track_caller]marked function downgrades the tail-call to a normal call (or equivalently tail-calls the shim made by fn def to fn ptr cast) (this pr)Ideally the downgrade would be performed by a MIR pass, but that requires post mono MIR opts (cc @saethlin, #131650). For now I've changed code in cg_ssa to accomodate this behaviour (+ added a hack to mono collector so that the shim is actually generated)
Additionally I added a lint, although I don't think it's strictly necessary.
Alternative to #144762 (and thus closes #144762)
Fixes #144755