Let a portion of DefPathHash uniquely identify the DefPath's crate.
This allows to directly map from a `DefPathHash` to the crate it originates from, without constructing side tables to do that mapping -- something that is useful for incremental compilation where we deal with `DefPathHash` instead of `DefId` a lot.
It also allows to reliably and cheaply check for `DefPathHash` collisions which allows the compiler to gracefully abort compilation instead of running into a subsequent ICE at some random place in the code.
The following new piece of documentation describes the most interesting aspects of the changes:
```rust
/// A `DefPathHash` is a fixed-size representation of a `DefPath` that is
/// stable across crate and compilation session boundaries. It consists of two
/// separate 64-bit hashes. The first uniquely identifies the crate this
/// `DefPathHash` originates from (see [StableCrateId]), and the second
/// uniquely identifies the corresponding `DefPath` within that crate. Together
/// they form a unique identifier within an entire crate graph.
///
/// There is a very small chance of hash collisions, which would mean that two
/// different `DefPath`s map to the same `DefPathHash`. Proceeding compilation
/// with such a hash collision would very probably lead to an ICE and, in the
/// worst case, to a silent mis-compilation. The compiler therefore actively
/// and exhaustively checks for such hash collisions and aborts compilation if
/// it finds one.
///
/// `DefPathHash` uses 64-bit hashes for both the crate-id part and the
/// crate-internal part, even though it is likely that there are many more
/// `LocalDefId`s in a single crate than there are individual crates in a crate
/// graph. Since we use the same number of bits in both cases, the collision
/// probability for the crate-local part will be quite a bit higher (though
/// still very small).
///
/// This imbalance is not by accident: A hash collision in the
/// crate-local part of a `DefPathHash` will be detected and reported while
/// compiling the crate in question. Such a collision does not depend on
/// outside factors and can be easily fixed by the crate maintainer (e.g. by
/// renaming the item in question or by bumping the crate version in a harmless
/// way).
///
/// A collision between crate-id hashes on the other hand is harder to fix
/// because it depends on the set of crates in the entire crate graph of a
/// compilation session. Again, using the same crate with a different version
/// number would fix the issue with a high probability -- but that might be
/// easier said then done if the crates in questions are dependencies of
/// third-party crates.
///
/// That being said, given a high quality hash function, the collision
/// probabilities in question are very small. For example, for a big crate like
/// `rustc_middle` (with ~50000 `LocalDefId`s as of the time of writing) there
/// is a probability of roughly 1 in 14,750,000,000 of a crate-internal
/// collision occurring. For a big crate graph with 1000 crates in it, there is
/// a probability of 1 in 36,890,000,000,000 of a `StableCrateId` collision.
```
Given the probabilities involved I hope that no one will ever actually see the error messages. Nonetheless, I'd be glad about some feedback on how to improve them. Should we create a GH issue describing the problem and possible solutions to point to? Or a page in the rustc book?
r? `@pnkfelix` (feel free to re-assign)
Output of `git log --oneline c68432f1e..970bc67c3`:
970bc67c3 (HEAD, origin/master, origin/auto-cargo, origin/HEAD) Auto merge of #9243 - wickerwaka:configurable-env-doc, r=ehuss
4d7a29b75 Document the configurable-env usntable option
f7a7a3f91 Auto merge of #9229 - alexcrichton:fix-borrow-mut, r=ehuss
3f2ece7a9 Fix a `BorrowMut` error when stdout is closed
7441e8c23 Auto merge of #8825 - Aaron1011:feature/report-future-incompat, r=ehuss
139ed73f5 Add future-incompat tracking issue number.
9ea350368 Fix some minor formatting issues.
f03d47ce4 Address review comments
6177c6584 Implement future incompatibility report support
c69409658 Auto merge of #9022 - nagisa:nagisa/manifest_path, r=alexcrichton
548300b20 Add the path to the manifest in json output
99e714c05 Auto merge of #9230 - kornelski:nobinaries, r=alexcrichton
61a31bc5f Auto merge of #9236 - kornelski:track-assert, r=Eh2406
3f7f0942c track_caller on custom assert functions
6977dee10 Explain `cargo install` is not for libraries
e4aebf0a0 Auto merge of #9231 - joshtriplett:clear-to-eol-if-color, r=alexcrichton
b219f0eb7 Auto merge of #9181 - jyn514:computer-says-no, r=ehuss
0b1816578 Remove unhelpful link to Cargo book
ea46f5ce3 Use ANSI clear-to-EOL if color is force-enabled
a6394bcc1 Remove unnecessary `config` argument to `Features::add`
3a86ecf2d Fix TODO about nightly features
09677c83c Be less unix-centric in error messages
ecfdced0d Fix test that assumed tests always were run on the stable channel
eba541994 Update comment in build_script_env
a5720117f Make `nightly_features_allowed` a field instead of a function
169b09ce7 Compute `enable_nightly_features` once instead of on each call
8fc86e155 Remove unused thread_locals
4b096beae Fix `masquerade_as_nightly_cargo` in work threads
e56417c8c Suggest RUSTC_BOOTSTRAP=crate instead of RUSTC_BOOTSTRAP=1
418129dae Downgrade error to a warning when `RUSTC_BOOTSTRAP` is set or this is the nightly channel
6c422a2c0 Restrict RUSTC_BOOTSTRAP in build.rs
Use u32 over Option<u32> in DebugLoc
~~Changes `Option<u32>` fields in `DebugLoc` to `Option<NonZeroU32>`. Since the respective fields (`line` and `col`) are guaranteed to be 1-based, this layout optimization is a freebie.~~
EDIT: Changes `Option<u32>` fields in `DebugLoc` to `u32`. As `@bugadani` pointed out, an `Option<NonZeroU32>` is probably an unnecessary layer of abstraction since the `None` variant is always used as `UNKNOWN_LINE_NUMBER` (which is just `0`). Also, `SourceInfo` in `metadata.rs` already uses a `u32` instead of an `Option<u32>` to encode the same information, so I think this change is warranted.
Since `@jyn514` raised some concerns over measuring performance in a similar PR (#82255), does this need a perf run?
As discussed in the issue tracker for the wg-allocators working group[1], updating this implementation for allocator support was most likely just forgotten in the original PR.
[1]: https://github.com/rust-lang/wg-allocators/issues/86
Sync rustc_codegen_cranelift
The main highlight of this sync is removal of support for the old x86 Cranelift backend. This made it possible to use native atomic instructions rather than hackishly using a global mutex. 128bit integer support has also seen a few bugfixes and performance improvements. And finally I have formatted everything using the same rustfmt config as the rest of this repo.
r? ````@ghost````
````@rustbot```` label +A-codegen +A-cranelift +T-compiler
rustdoc: Add an unstable option to print all unversioned files
This allows sharing those files between different doc invocations
without having to know their names ahead of time.
Helps with https://github.com/rust-lang/docs.rs/issues/1302.
r? ````@GuillaumeGomez```` cc ````@pietroalbini```` ````@Nemo157````
improve offset_from docs
`@thomcc` pointed out that the current docs leave it kind of unclear how one can satisfy the "no wrapping around `isize` or the address space" requirement of `offset_from`, so make the docs clearer about that.
FWIW, I don't think I entirely agree with that second paragraph about large objects (that I left mostly unchanged here). LLVM, to my knowledge, fundamentally assumes that all allocations fit into an `isize::MAX`. So in that sense creating a larger allocation is simply UB. I would expect a guarantee that Rust heap allocation methods will never return allocations larger than `isize::MAX` (or rather, Rust heap allocation methods should require that the `Layout` is no larger than `isize::MAX`). However, I cannot find any such requirement documented currently. Large allocations are not mentioned at all in the allocator docs, which is quite surprising -- even if we say that such allocations are not insta-UB (which I think is incompatible with LLVM), they are still extremely footgunny since `ptr::offset`/`ptr::add` do not support offsetting by more than `isize::MAX` bytes.
Furthermore, the allocator docs don't even say anything about allocations wrapping around the address space. But that is certainly something allocators must ensure never happens; we cannot expect clients to defend against this.
Cc `@rust-lang/wg-allocators`
Cleanup rustdoc warnings
## Clean up error reporting for deprecated passes
Using `error!` here goes all the way back to the original commit, https://github.com/rust-lang/rust/pull/8540. I don't see any reason to use logging; rustdoc should use diagnostics wherever possible. See https://github.com/rust-lang/rust/pull/81932#issuecomment-785291244 for further context.
- Use spans for deprecated attributes
- Use a proper diagnostic for unknown passes, instead of error logging
- Add tests for unknown passes
- Improve some wording in diagnostics
## Report that `doc(plugins)` doesn't work using diagnostics instead of `eprintln!`
This also adds a test for the output.
This was added in https://github.com/rust-lang/rust/pull/52194. I don't see any particular reason not to use diagnostics here, I think it was just missed in https://github.com/rust-lang/rust/pull/50541.
Improve transmute docs with further clarifications
Closes#82493.
Please let me know if any of the new wording sounds off, English is not my mother tongue.
Remove RefCell around `module_trait_cache`
This builds on https://github.com/rust-lang/rust/pull/82018 and should not be merged before.
## Don't require a `DocContext` for `report_diagnostic`
This is needed for the next commit, which needs mutable access to the `cx` from
within the `decorate` closure.
- Change `as_local_hir_id` to an associated function, since it only
needs a `TyCtxt`
- Change `source_span_for_markdown_range` to only take a `TyCtxt`
## Remove RefCell around module_trait_cache
This is mostly just changing lots of functions from `&DocContext` to `&mut DocContext`.
Prevent specialized ZipImpl from calling `__iterator_get_unchecked` twice with the same index
Fixes#82291
It's open for review, but conflicts with #82289, wait before merging. The conflict involves only the new test, so it should be rather trivial to fix.
Make some Option, Result methods unstably const
The following methods are now unstably const:
- Option::transpose
- Option::flatten
- Result::flatten
While some methods for could likely be made `const` in the future, nearly all of them require something to be dropped at compile-time, which isn't currently supported. The functions listed above should have a trivial path to stabilization.
Change built-in kernel targets to be os = none throughout
Whether for Rust's own `target_os`, LLVM's triples, or GNU config's, the
OS-related have fields have been for code running *on* that OS, not code
hat is *part* of the OS.
The difference is huge, as syscall interfaces are nothing like
freestanding interfaces. Kernels are (hypervisors and other more exotic
situations aside) freestanding programs that use the interfaces provided
by the hardware. It's *those* interfaces, the ones external to the
program being built and its software dependencies, that are the content
of the target.
For the Linux Kernel in particular, `target_env: "gnu"` is removed for
the same reason: that `-gnu` refers to glibc or GNU/linux, neither of
which applies to the kernel itself.
Relates to #74247
Move check only relevant in error case out of critical path
Move the check for potentially forgotten `return` in a tail expression
of arbitrary expressions into the coercion error branch to avoid
computing unncessary coercion checks on successful code.
Follow up to #81458.
Rust contains various size checks conditional on target_arch = "x86_64",
but these checks were never intended to apply to
x86_64-unknown-linux-gnux32. Add target_pointer_width = "64" to the
conditions.
I don't think the boxing helped performance, in fact I think it
potentially made it worse. The data was still being copied, but now it
was through a pointer. Thinking about it more, I think boxing might only
help when you're passing a big object around by value all the time,
rather than the slowdown being that you're cloning it.
There was no need to clone `id_map` because it was reset before each
item was rendered. `deref_id_map` was not reset, but it was keyed by
`DefId` and thus was unlikely to have collisions (at least for now).
Now we just clone the fields that need to be cloned, and instead create
fresh versions of the others.
