Reduce formatting `width` and `precision` to 16 bits
This is part of https://github.com/rust-lang/rust/issues/99012
This is reduces the `width` and `precision` fields in format strings to 16 bits. They are currently full `usize`s, but it's a bit nonsensical that we need to support the case where someone wants to pad their value to eighteen quintillion spaces and/or have eighteen quintillion digits of precision.
By reducing these fields to 16 bit, we can reduce `FormattingOptions` to 64 bits (see https://github.com/rust-lang/rust/pull/136974) and improve the in memory representation of `format_args!()`. (See additional context below.)
This also fixes a bug where the width or precision is silently truncated when cross-compiling to a target with a smaller `usize`. By reducing the width and precision fields to the minimum guaranteed size of `usize`, 16 bits, this bug is eliminated.
This is a breaking change, but affects almost no existing code.
---
Details of this change:
There are three ways to set a width or precision today:
1. Directly a formatting string, e.g. `println!("{a:1234}")`
2. Indirectly in a formatting string, e.g. `println!("{a:width$}", width=1234)`
3. Through the unstable `FormattingOptions::width` method.
This PR:
- Adds a compiler error for 1. (`println!("{a:9999999}")` no longer compiles and gives a clear error.)
- Adds a runtime check for 2. (`println!("{a:width$}, width=9999999)` will panic.)
- Changes the signatures of the (unstable) `FormattingOptions::[get_]width` methods to use a `u16` instead.
---
Additional context for improving `FormattingOptions` and `fmt::Arguments`:
All the formatting flags and options are currently:
- The `+` flag (1 bit)
- The `-` flag (1 bit)
- The `#` flag (1 bit)
- The `0` flag (1 bit)
- The `x?` flag (1 bit)
- The `X?` flag (1 bit)
- The alignment (2 bits)
- The fill character (21 bits)
- Whether a width is specified (1 bit)
- Whether a precision is specified (1 bit)
- If used, the width (a full usize)
- If used, the precision (a full usize)
Everything except the last two can simply fit in a `u32` (those add up to 31 bits in total).
If we can accept a max width and precision of u16::MAX, we can make a `FormattingOptions` that is exactly 64 bits in size; the same size as a thin reference on most platforms.
If, additionally, we also limit the number of formatting arguments, we can also reduce the size of `fmt::Arguments` (that is, of a `format_args!()` expression).
Revert "Use workspace lints for crates in `compiler/` #138084"
Revert <https://github.com/rust-lang/rust/pull/138084> to buy time to consider options that avoids breaking downstream usages of cargo on distributed `rustc-src` artifacts, where such cargo invocations fail due to inability to inherit `lints` from workspace root manifest's `workspace.lints` (this is only valid for the source rust-lang/rust workspace, but not really the distributed `rustc-src` artifacts). The problem is that the `rustc-src` component doesn't include the root `Cargo.toml` manifest.
This breakage was reported in https://github.com/rust-lang/rust/issues/138304.
This reverts commit 48caf81484b50dca5a5cebb614899a3df81ca898, reversing changes made to c6662879b27f5161e95f39395e3c9513a7b97028.
cc `@RalfJung`
r? `@nnethercote` (sorry, I didn't consider this being a thing 💀)
Fix post-merge workflow
I forgot that `actions/checkout` only checks out a single commit by default. I also forgot to set the environment variable required for the `gh` CLI commands.
I did a few more tests on my fork and hopefully now it should work properly. I also tested it with fake rollup PRs and the comment was sent only to the merged rollup, as it should be.
r? `@marcoieni`
Fix dyn -> param suggestion in struct ICEs
Makes the logic from #138042 a bit less ICEy and more clean. Also fixes an incorrect suggestion when the struct already has generics. I'll point out the major changes and observations in the code.
Fixes#138229Fixes#138211
r? nnethercote since you reviewed the original pr, or re-roll if you don't want to review this
Add a test for `-znostart-stop-gc` usage with LLD
This test replicates the behavior of https://github.com/dtolnay/linkme, to test that it still works even with LLD. Without `-znostart-stop-gc` the test fails.
r? ``@lqd``
try-job: x86_64-gnu
try-job: x86_64-msvc-1
Update cargo
22 commits in 2622e844bc1e2e6123e54e94e4706f7b6195ce3d..ab1463d632528e39daf35f263e10c14cbe590ce8
2025-02-28 12:33:57 +0000 to 2025-03-08 01:45:05 +0000
- test: redact host target when comparing CARGO_ENV path (rust-lang/cargo#15279)
- feat: add completions for install --path (rust-lang/cargo#15266)
- fix(package): report lockfile / workspace manifest is dirty (rust-lang/cargo#15276)
- feat(tree): Add `--depth public` behind `-Zunstable-options` (rust-lang/cargo#15243)
- Don't use `$CARGO_BUILD_TARGET` in `cargo metadata` (rust-lang/cargo#15271)
- feat: show extra build description from bootstrap (rust-lang/cargo#15269)
- Upgrade to `rustc-stable-hash v0.1.2` (rust-lang/cargo#15268)
- fix: Respect --frozen everywhere --offline or --locked is accepted (rust-lang/cargo#15263)
- feat(tree): Color the output (rust-lang/cargo#15242)
- fix(vendor): dont remove non-cached source (rust-lang/cargo#15260)
- docs: lockfile is always included since 1.84 (rust-lang/cargo#15257)
- Remove `Cargo.toml` from `package.include` in example (rust-lang/cargo#15253)
- Small cleanup: remove unneeded result (rust-lang/cargo#15256)
- Fix typo in build-scripts.md (rust-lang/cargo#15254)
- chore(deps): update rust crate pulldown-cmark to 0.13.0 (rust-lang/cargo#15250)
- chore(deps): update compatible (rust-lang/cargo#15249)
- feat(cli): forward bash completions of third party subcommands (rust-lang/cargo#15247)
- feat: add completions for `--lockfile-path` (rust-lang/cargo#15238)
- fix: reset $CARGO if the running program is real `cargo[.exe]` (rust-lang/cargo#15208)
- Get all members as `available targets` even though default-members was specified. (rust-lang/cargo#15199)
- refactor: control byte display precision with std::fmt options (rust-lang/cargo#15246)
- fix(package): Ensure we can package directories ending with '.rs' (rust-lang/cargo#15240)
Rollup of 12 pull requests
Successful merges:
- #136127 (Allow `*const W<dyn A> -> *const dyn A` ptr cast)
- #136968 (Turn order dependent trait objects future incompat warning into a hard error)
- #137319 (Stabilize `const_vec_string_slice`)
- #137885 (tidy: add triagebot checks)
- #138040 (compiler: Use `size_of` from the prelude instead of imported)
- #138084 (Use workspace lints for crates in `compiler/`)
- #138158 (Move more layouting logic to `rustc_abi`)
- #138160 (depend more on attr_data_structures and move find_attr! there)
- #138192 (crashes: couple more tests)
- #138216 (bootstrap: Fix stack printing when a step cycle is detected)
- #138232 (Reduce verbosity of GCC build log)
- #138242 (Revert "Don't test new error messages with the stage 0 compiler")
r? `@ghost`
`@rustbot` modify labels: rollup
bootstrap: Fix stack printing when a step cycle is detected
When bootstrap detects a step dependency cycle (which represents a bootstrap bug), it is supposed to print out the contents of the step stack as part of its panic message.
However, while investigating #138205 it was found that bootstrap was actually printing out several copies of `Any { .. }`, because that is the Debug implementation for `dyn Any`. This is sadly not very helpful.
This PR fixes that problem by introducing a `trait AnyDebug: Any + Debug` that delegates to the underlying type's Debug implementation, while still allowing downcasting via Any.
---
The fixed behaviour can be verified manually (and is tested automatically) via a new dummy command, `./x run cyclic-step`:
```
$ x run cyclic-step
Building bootstrap
Finished `dev` profile [unoptimized] target(s) in 0.02s
thread 'main' panicked at src/bootstrap/src/core/builder/mod.rs:1521:17:
Cycle in build detected when adding CyclicStep { n: 0 }
CyclicStep { n: 0 }
CyclicStep { n: 1 }
CyclicStep { n: 2 }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Build completed unsuccessfully in 0:00:00
```
depend more on attr_data_structures and move find_attr! there
r? ``@oli-obk``
This should be an easy one. It just moves some imports around. This is necessary for other changes that I'm working on not to have import cycles. However, it's an easy one to just merge on its own.
Move more layouting logic to `rustc_abi`
Move all `LayoutData`-constructing code to `rustc_abi`:
- Infaillible operations get a new `LayoutData` constructor method;
- Faillible ones get a new method on `LayoutCalculator`.
compiler: Use `size_of` from the prelude instead of imported
Use `std::mem::{size_of, size_of_val, align_of, align_of_val}` from the prelude instead of importing or qualifying them. Apply this change across the compiler.
These functions were added to all preludes in Rust 1.80.
r? ``@compiler-errors``
Change TaskDeps to start preallocated with 128 capacity
This is a tiny change that makes `TaskDeps::read_set` start preallocated with capacity for 128 elements.
From local profiling, it looks like `TaskDeps::read_set` is one of the most-often resized hash-sets in `rustc`.
