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Remove effect of #[no_link]
attribute on name resolution
#92034
Conversation
(rust-highfive has picked a reviewer for you, use r? to override) |
Previously it hid all non-macro names from other crates. This has no relation to linking and can change name resolution behavior in some cases (e.g. glob conflicts), in addition to just producing the "unresolved name" errors
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@@ -1099,10 +1099,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> { | |||
}; | |||
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// Iterate over all children. | |||
let macros_only = self.dep_kind.lock().macros_only(); |
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The macros_only
flag is only set for proc macro crates (processed above), and for #[no_link]
crates.
Maybe it should be renamed, but I don't want to do it in a single PR with observable language changes.
I agree that this seems like a generally good change. It feels like we should deprecate no_link, perhaps with a future-compat warning and/or removal planned in the next edition. Searching on github it looks like most usage is related to macro crates, but I suspect likely not in a way that is actually necessary -- if we do try to deprecate/remove, it might make sense to try and more intentionally test these. I have a mild sense of the pre-existing behavior being better in the sense that it prevents linker errors (which are generally bad), but it seems like we should be able to improve diagnostics there if there's an actual use case (through changes in mono item collection, I suppose). But given the general lack of need for something like this it doesn't seem like a good end-goal to pursue. @petrochenkov to make sure I'm parsing the issue description right: it sounds like the "breaking" change here is enabling the use of non-macro names changing glob imports to potentially now conflict/resolve to different items? Nominating for T-lang to look at in a meeting, though it feels like FCP might be a bit excessive (given the rather low likelihood of any potential cases where this changes behavior on old code). |
Yes, the changing case may look like this: extern crate link_crate; // also has function `foo` in the root
#[no_link] extern crate no_link_crate; // has function `foo` in the root
use link_crate::*; // imports function `foo`
use nolink_crate::*; // before this PR: doesn't import function `foo`
// after this PR: imports function `foo` - conflict if `foo` is used
fn main() { foo(); } // `foo` is used This is equivalent to adding new items to any library crate, which is generally not considered a semver-breaking change. |
This seems like a good change. If we are concerned about linker errors, I'd prefer we detect and enforce those after the fact rather than having name resolution not have the names in the first place. |
We discussed this in today's @rust-lang/lang meeting, and agreed that we want to make this change and simplify name resolution. Also, if people regularly use this attribute, we should consider a version that attaches to @rfcbot merge |
Team member @joshtriplett has proposed to merge this. The next step is review by the rest of the tagged team members: No concerns currently listed. Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up! See this document for info about what commands tagged team members can give me. |
🔔 This is now entering its final comment period, as per the review above. 🔔 |
The final comment period, with a disposition to merge, as per the review above, is now complete. As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed. This will be merged soon. |
@bors r+ |
📌 Commit 54cd824 has been approved by |
☀️ Test successful - checks-actions |
Finished benchmarking commit (f7934f6): comparison url. Summary: This benchmark run did not return any relevant changes. If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf. @rustbot label: -perf-regression |
Pkgsrc changes: * Bump available bootstraps to 1.58.1. * Adjust one patch (and checksum) so that it still applies. Upstream changes: Version 1.59.0 (2022-02-24) ========================== Language -------- - [Stabilize default arguments for const generics][90207] - [Stabilize destructuring assignment][90521] - [Relax private in public lint on generic bounds and where clauses of trait impls][90586] - [Stabilize asm! and global_asm! for x86, x86_64, ARM, Aarch64, and RISC-V][91728] Compiler -------- - [Stabilize new symbol mangling format, leaving it opt-in (-Csymbol-mangling-version=v0)][90128] - [Emit LLVM optimization remarks when enabled with `-Cremark`][90833] - [Fix sparc64 ABI for aggregates with floating point members][91003] - [Warn when a `#[test]`-like built-in attribute macro is present multiple times.][91172] - [Add support for riscv64gc-unknown-freebsd][91284] - [Stabilize `-Z emit-future-incompat` as `--json future-incompat`][91535] - [Soft disable incremental compilation][94124] This release disables incremental compilation, unless the user has explicitly opted in via the newly added RUSTC_FORCE_INCREMENTAL=1 environment variable. This is due to a known and relatively frequently occurring bug in incremental compilation, which causes builds to issue internal compiler errors. This particular bug is already fixed on nightly, but that fix has not yet rolled out to stable and is deemed too risky for a direct stable backport. As always, we encourage users to test with nightly and report bugs so that we can track failures and fix issues earlier. See [94124] for more details. [94124]: rust-lang/rust#94124 Libraries --------- - [Remove unnecessary bounds for some Hash{Map,Set} methods][91593] Stabilized APIs --------------- - [`std::thread::available_parallelism`][available_parallelism] - [`Result::copied`][result-copied] - [`Result::cloned`][result-cloned] - [`arch::asm!`][asm] - [`arch::global_asm!`][global_asm] - [`ops::ControlFlow::is_break`][is_break] - [`ops::ControlFlow::is_continue`][is_continue] - [`TryFrom<char> for u8`][try_from_char_u8] - [`char::TryFromCharError`][try_from_char_err] implementing `Clone`, `Debug`, `Display`, `PartialEq`, `Copy`, `Eq`, `Error` - [`iter::zip`][zip] - [`NonZeroU8::is_power_of_two`][is_power_of_two8] - [`NonZeroU16::is_power_of_two`][is_power_of_two16] - [`NonZeroU32::is_power_of_two`][is_power_of_two32] - [`NonZeroU64::is_power_of_two`][is_power_of_two64] - [`NonZeroU128::is_power_of_two`][is_power_of_two128] - [`DoubleEndedIterator for ToLowercase`][lowercase] - [`DoubleEndedIterator for ToUppercase`][uppercase] - [`TryFrom<&mut [T]> for [T; N]`][tryfrom_ref_arr] - [`UnwindSafe for Once`][unwindsafe_once] - [`RefUnwindSafe for Once`][refunwindsafe_once] - [armv8 neon intrinsics for aarch64][stdarch/1266] Const-stable: - [`mem::MaybeUninit::as_ptr`][muninit_ptr] - [`mem::MaybeUninit::assume_init`][muninit_init] - [`mem::MaybeUninit::assume_init_ref`][muninit_init_ref] - [`ffi::CStr::from_bytes_with_nul_unchecked`][cstr_from_bytes] Cargo ----- - [Stabilize the `strip` profile option][cargo/10088] - [Stabilize future-incompat-report][cargo/10165] - [Support abbreviating `--release` as `-r`][cargo/10133] - [Support `term.quiet` configuration][cargo/10152] - [Remove `--host` from cargo {publish,search,login}][cargo/10145] Compatibility Notes ------------------- - [Refactor weak symbols in std::sys::unix][90846] This may add new, versioned, symbols when building with a newer glibc, as the standard library uses weak linkage rather than dynamically attempting to load certain symbols at runtime. - [Deprecate crate_type and crate_name nested inside `#![cfg_attr]`][83744] This adds a future compatibility lint to supporting the use of cfg_attr wrapping either crate_type or crate_name specification within Rust files; it is recommended that users migrate to setting the equivalent command line flags. - [Remove effect of `#[no_link]` attribute on name resolution][92034] This may expose new names, leading to conflicts with preexisting names in a given namespace and a compilation failure. - [Cargo will document libraries before binaries.][cargo/10172] - [Respect doc=false in dependencies, not just the root crate][cargo/10201] - [Weaken guarantee around advancing underlying iterators in zip][83791] - [Make split_inclusive() on an empty slice yield an empty output][89825] - [Update std::env::temp_dir to use GetTempPath2 on Windows when available.][89999] - [unreachable! was updated to match other formatting macro behavior on Rust 2021][92137] Internal Changes ---------------- These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools. - [Fix many cases of normalization-related ICEs][91255] - [Replace dominators algorithm with simple Lengauer-Tarjan][85013] - [Store liveness in interval sets for region inference][90637] - [Remove `in_band_lifetimes` from the compiler and standard library, in preparation for removing this unstable feature.][91867] [91867]: rust-lang/rust#91867 [83744]: rust-lang/rust#83744 [83791]: rust-lang/rust#83791 [85013]: rust-lang/rust#85013 [89825]: rust-lang/rust#89825 [89999]: rust-lang/rust#89999 [90128]: rust-lang/rust#90128 [90207]: rust-lang/rust#90207 [90521]: rust-lang/rust#90521 [90586]: rust-lang/rust#90586 [90637]: rust-lang/rust#90637 [90833]: rust-lang/rust#90833 [90846]: rust-lang/rust#90846 [91003]: rust-lang/rust#91003 [91172]: rust-lang/rust#91172 [91255]: rust-lang/rust#91255 [91284]: rust-lang/rust#91284 [91535]: rust-lang/rust#91535 [91593]: rust-lang/rust#91593 [91728]: rust-lang/rust#91728 [91878]: rust-lang/rust#91878 [91896]: rust-lang/rust#91896 [91926]: rust-lang/rust#91926 [91984]: rust-lang/rust#91984 [92020]: rust-lang/rust#92020 [92034]: rust-lang/rust#92034 [92483]: rust-lang/rust#92483 [cargo/10088]: rust-lang/cargo#10088 [cargo/10133]: rust-lang/cargo#10133 [cargo/10145]: rust-lang/cargo#10145 [cargo/10152]: rust-lang/cargo#10152 [cargo/10165]: rust-lang/cargo#10165 [cargo/10172]: rust-lang/cargo#10172 [cargo/10201]: rust-lang/cargo#10201 [cargo/10269]: rust-lang/cargo#10269 [cstr_from_bytes]: https://doc.rust-lang.org/stable/std/ffi/struct.CStr.html#method.from_bytes_with_nul_unchecked [muninit_ptr]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.as_ptr [muninit_init]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init [muninit_init_ref]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_ref [unwindsafe_once]: https://doc.rust-lang.org/stable/std/sync/struct.Once.html#impl-UnwindSafe [refunwindsafe_once]: https://doc.rust-lang.org/stable/std/sync/struct.Once.html#impl-RefUnwindSafe [tryfrom_ref_arr]: https://doc.rust-lang.org/stable/std/convert/trait.TryFrom.html#impl-TryFrom%3C%26%27_%20mut%20%5BT%5D%3E [lowercase]: https://doc.rust-lang.org/stable/std/char/struct.ToLowercase.html#impl-DoubleEndedIterator [uppercase]: https://doc.rust-lang.org/stable/std/char/struct.ToUppercase.html#impl-DoubleEndedIterator [try_from_char_err]: https://doc.rust-lang.org/stable/std/char/struct.TryFromCharError.html [available_parallelism]: https://doc.rust-lang.org/stable/std/thread/fn.available_parallelism.html [result-copied]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.copied [result-cloned]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.cloned [asm]: https://doc.rust-lang.org/stable/core/arch/macro.asm.html [global_asm]: https://doc.rust-lang.org/stable/core/arch/macro.global_asm.html [is_break]: https://doc.rust-lang.org/stable/std/ops/enum.ControlFlow.html#method.is_break [is_continue]: https://doc.rust-lang.org/stable/std/ops/enum.ControlFlow.html#method.is_continue [try_from_char_u8]: https://doc.rust-lang.org/stable/std/primitive.char.html#impl-TryFrom%3Cchar%3E [zip]: https://doc.rust-lang.org/stable/std/iter/fn.zip.html [is_power_of_two8]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU8.html#method.is_power_of_two [is_power_of_two16]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU16.html#method.is_power_of_two [is_power_of_two32]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU32.html#method.is_power_of_two [is_power_of_two64]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU64.html#method.is_power_of_two [is_power_of_two128]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU128.html#method.is_power_of_two [stdarch/1266]: rust-lang/stdarch#1266
Pkgsrc changes: * Bump available bootstraps to 1.58.1. * Adjust one patch (and checksum) so that it still applies. Upstream changes: Version 1.59.0 (2022-02-24) ========================== Language -------- - [Stabilize default arguments for const generics][90207] - [Stabilize destructuring assignment][90521] - [Relax private in public lint on generic bounds and where clauses of trait impls][90586] - [Stabilize asm! and global_asm! for x86, x86_64, ARM, Aarch64, and RISC-V][91728] Compiler -------- - [Stabilize new symbol mangling format, leaving it opt-in (-Csymbol-mangling-version=v0)][90128] - [Emit LLVM optimization remarks when enabled with `-Cremark`][90833] - [Fix sparc64 ABI for aggregates with floating point members][91003] - [Warn when a `#[test]`-like built-in attribute macro is present multiple times.][91172] - [Add support for riscv64gc-unknown-freebsd][91284] - [Stabilize `-Z emit-future-incompat` as `--json future-incompat`][91535] - [Soft disable incremental compilation][94124] This release disables incremental compilation, unless the user has explicitly opted in via the newly added RUSTC_FORCE_INCREMENTAL=1 environment variable. This is due to a known and relatively frequently occurring bug in incremental compilation, which causes builds to issue internal compiler errors. This particular bug is already fixed on nightly, but that fix has not yet rolled out to stable and is deemed too risky for a direct stable backport. As always, we encourage users to test with nightly and report bugs so that we can track failures and fix issues earlier. See [94124] for more details. [94124]: rust-lang/rust#94124 Libraries --------- - [Remove unnecessary bounds for some Hash{Map,Set} methods][91593] Stabilized APIs --------------- - [`std::thread::available_parallelism`][available_parallelism] - [`Result::copied`][result-copied] - [`Result::cloned`][result-cloned] - [`arch::asm!`][asm] - [`arch::global_asm!`][global_asm] - [`ops::ControlFlow::is_break`][is_break] - [`ops::ControlFlow::is_continue`][is_continue] - [`TryFrom<char> for u8`][try_from_char_u8] - [`char::TryFromCharError`][try_from_char_err] implementing `Clone`, `Debug`, `Display`, `PartialEq`, `Copy`, `Eq`, `Error` - [`iter::zip`][zip] - [`NonZeroU8::is_power_of_two`][is_power_of_two8] - [`NonZeroU16::is_power_of_two`][is_power_of_two16] - [`NonZeroU32::is_power_of_two`][is_power_of_two32] - [`NonZeroU64::is_power_of_two`][is_power_of_two64] - [`NonZeroU128::is_power_of_two`][is_power_of_two128] - [`DoubleEndedIterator for ToLowercase`][lowercase] - [`DoubleEndedIterator for ToUppercase`][uppercase] - [`TryFrom<&mut [T]> for [T; N]`][tryfrom_ref_arr] - [`UnwindSafe for Once`][unwindsafe_once] - [`RefUnwindSafe for Once`][refunwindsafe_once] - [armv8 neon intrinsics for aarch64][stdarch/1266] Const-stable: - [`mem::MaybeUninit::as_ptr`][muninit_ptr] - [`mem::MaybeUninit::assume_init`][muninit_init] - [`mem::MaybeUninit::assume_init_ref`][muninit_init_ref] - [`ffi::CStr::from_bytes_with_nul_unchecked`][cstr_from_bytes] Cargo ----- - [Stabilize the `strip` profile option][cargo/10088] - [Stabilize future-incompat-report][cargo/10165] - [Support abbreviating `--release` as `-r`][cargo/10133] - [Support `term.quiet` configuration][cargo/10152] - [Remove `--host` from cargo {publish,search,login}][cargo/10145] Compatibility Notes ------------------- - [Refactor weak symbols in std::sys::unix][90846] This may add new, versioned, symbols when building with a newer glibc, as the standard library uses weak linkage rather than dynamically attempting to load certain symbols at runtime. - [Deprecate crate_type and crate_name nested inside `#![cfg_attr]`][83744] This adds a future compatibility lint to supporting the use of cfg_attr wrapping either crate_type or crate_name specification within Rust files; it is recommended that users migrate to setting the equivalent command line flags. - [Remove effect of `#[no_link]` attribute on name resolution][92034] This may expose new names, leading to conflicts with preexisting names in a given namespace and a compilation failure. - [Cargo will document libraries before binaries.][cargo/10172] - [Respect doc=false in dependencies, not just the root crate][cargo/10201] - [Weaken guarantee around advancing underlying iterators in zip][83791] - [Make split_inclusive() on an empty slice yield an empty output][89825] - [Update std::env::temp_dir to use GetTempPath2 on Windows when available.][89999] - [unreachable! was updated to match other formatting macro behavior on Rust 2021][92137] Internal Changes ---------------- These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools. - [Fix many cases of normalization-related ICEs][91255] - [Replace dominators algorithm with simple Lengauer-Tarjan][85013] - [Store liveness in interval sets for region inference][90637] - [Remove `in_band_lifetimes` from the compiler and standard library, in preparation for removing this unstable feature.][91867] [91867]: rust-lang/rust#91867 [83744]: rust-lang/rust#83744 [83791]: rust-lang/rust#83791 [85013]: rust-lang/rust#85013 [89825]: rust-lang/rust#89825 [89999]: rust-lang/rust#89999 [90128]: rust-lang/rust#90128 [90207]: rust-lang/rust#90207 [90521]: rust-lang/rust#90521 [90586]: rust-lang/rust#90586 [90637]: rust-lang/rust#90637 [90833]: rust-lang/rust#90833 [90846]: rust-lang/rust#90846 [91003]: rust-lang/rust#91003 [91172]: rust-lang/rust#91172 [91255]: rust-lang/rust#91255 [91284]: rust-lang/rust#91284 [91535]: rust-lang/rust#91535 [91593]: rust-lang/rust#91593 [91728]: rust-lang/rust#91728 [91878]: rust-lang/rust#91878 [91896]: rust-lang/rust#91896 [91926]: rust-lang/rust#91926 [91984]: rust-lang/rust#91984 [92020]: rust-lang/rust#92020 [92034]: rust-lang/rust#92034 [92483]: rust-lang/rust#92483 [cargo/10088]: rust-lang/cargo#10088 [cargo/10133]: rust-lang/cargo#10133 [cargo/10145]: rust-lang/cargo#10145 [cargo/10152]: rust-lang/cargo#10152 [cargo/10165]: rust-lang/cargo#10165 [cargo/10172]: rust-lang/cargo#10172 [cargo/10201]: rust-lang/cargo#10201 [cargo/10269]: rust-lang/cargo#10269 [cstr_from_bytes]: https://doc.rust-lang.org/stable/std/ffi/struct.CStr.html#method.from_bytes_with_nul_unchecked [muninit_ptr]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.as_ptr [muninit_init]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init [muninit_init_ref]: https://doc.rust-lang.org/stable/std/mem/union.MaybeUninit.html#method.assume_init_ref [unwindsafe_once]: https://doc.rust-lang.org/stable/std/sync/struct.Once.html#impl-UnwindSafe [refunwindsafe_once]: https://doc.rust-lang.org/stable/std/sync/struct.Once.html#impl-RefUnwindSafe [tryfrom_ref_arr]: https://doc.rust-lang.org/stable/std/convert/trait.TryFrom.html#impl-TryFrom%3C%26%27_%20mut%20%5BT%5D%3E [lowercase]: https://doc.rust-lang.org/stable/std/char/struct.ToLowercase.html#impl-DoubleEndedIterator [uppercase]: https://doc.rust-lang.org/stable/std/char/struct.ToUppercase.html#impl-DoubleEndedIterator [try_from_char_err]: https://doc.rust-lang.org/stable/std/char/struct.TryFromCharError.html [available_parallelism]: https://doc.rust-lang.org/stable/std/thread/fn.available_parallelism.html [result-copied]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.copied [result-cloned]: https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.cloned [asm]: https://doc.rust-lang.org/stable/core/arch/macro.asm.html [global_asm]: https://doc.rust-lang.org/stable/core/arch/macro.global_asm.html [is_break]: https://doc.rust-lang.org/stable/std/ops/enum.ControlFlow.html#method.is_break [is_continue]: https://doc.rust-lang.org/stable/std/ops/enum.ControlFlow.html#method.is_continue [try_from_char_u8]: https://doc.rust-lang.org/stable/std/primitive.char.html#impl-TryFrom%3Cchar%3E [zip]: https://doc.rust-lang.org/stable/std/iter/fn.zip.html [is_power_of_two8]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU8.html#method.is_power_of_two [is_power_of_two16]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU16.html#method.is_power_of_two [is_power_of_two32]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU32.html#method.is_power_of_two [is_power_of_two64]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU64.html#method.is_power_of_two [is_power_of_two128]: https://doc.rust-lang.org/stable/core/num/struct.NonZeroU128.html#method.is_power_of_two [stdarch/1266]: rust-lang/stdarch#1266
Previously it hid all non-macro names from other crates.
This has no relation to linking and can change name resolution behavior in some cases (e.g. glob conflicts), in addition to just producing the "unresolved name" errors.
I can kind of understand the possible reasoning behind the current behavior - if you can use names from a
no_link
crates then you can use, for example, functions too, but whether it will actually work or produce link-time errors will depend on random factors like inliner behavior.(^^^ This is not the actual reason why the current behavior exist, I've looked through git history and it's mostly accidental.)
I think this risk is ok for such an obscure attribute, and we don't need to specifically prevent use of non-macro items from such crates.
(I'm not actually sure why would anyone use
#[no_link]
on a crate, even if it's macro only, if you aware of any use cases, please share. IIRC, at some point it was used for crates implementing custom derives - the now removed legacy ones, not the current proc macros.)Extracted from #91795.