Shorten some dependency chains in the compiler
(I recommend reviewing this commit by commit.)
One of the long dependency chains in the compiler is:
- Many things depend on `rustc_errors`.
- `rustc_errors` depended on many things prior to this PR, including `rustc_target`, `rustc_type_ir`, `rustc_hir`, and `rustc_lint_defs`.
- `rustc_lint_defs` depended on `rustc_hir` prior to this PR.
- `rustc_hir` depends on `rustc_target`.
- `rustc_target` is large and takes a while.
This PR breaks that chain, through a few steps:
- The `IntoDiagArgs` trait, from `rustc_errors`, moves earlier in the dependency chain. This allows `rustc_errors` to stop depending on a pile of crates just to implement `IntoDiagArgs` for their types.
- Split `rustc_hir_id` out of `rustc_hir`, so crates that just need `HirId` and similar don't depend on all of `rust_hir` (and thus `rustc_target`).
- Make `rustc_lint_defs` stop depending on `rustc_hir`.
Add new `--test-codegen-backend` bootstrap option
This new bootstrap command line flag allows to do:
```shell
./x.py test tests/ui/intrinsics/panic-uninitialized-zeroed.rs --stage 1 -j8 --test-codegen-backend gcc
```
This is the last step before running it into the CI.
Supersedes rust-lang/rust#144687.
r? ``````@Kobzol``````
Fix rustc uplifting (take two)
The rustc uplifting logic is really annoying.. https://github.com/rust-lang/rust/pull/145557 was not enough to fix it.
Consider https://github.com/rust-lang/rust/issues/145534#issuecomment-3201868888: in this situation, we do a stage3 build of a cross-compiled rustc (it happens because we run `x test --stage 2`, which mistakenly builds a stage3 rustc, but it doesn't matter what casuses it, what matters is that the stage3 build isn't working).
Currently, a stage3 cross-compiled build of rustc works like this:
1) stage0 (host) -> stage1 (host)
2) stage1 (host) -> stage2 (host)
3) stage2 (host) -> stage3 (target)
The problem is that in the uplifting logic, I assumed that we will have a stage2 (target) rustc available, which we can uplift. And that would indeed be an ideal solution. But currently, we will actually build a stage2 (*host*) rustc, and only then start the cross-compilation. So the uplifting is broken.
I spend a couple of hours trying to fix this, and do the uplifting "from the other direction", so that already when we assemble a stage3 rustc, we notice that an uplift should happen, and we only build stage1 (host) rustc, which also helps avoid one needless rustc build. However, this was relatively complicated and would require larger changes that I was not confident landing at this time.
So instead I decided to do a much simpler fix, and just disable rustc uplifting when cross-compiling. Since we currently do the `stage2 (host) -> stage3 (target)` step, it should not actually affect stage3 cross-compiled builds in any way (I hope..), and should only affect stage4+ builds, about which I don't really care (the only change there should be more rustc builds). For normal builds, the stage2 host rustc should (hopefully) always be present, so we shouldn't run into this issue.
Eventually, I would like to remove rustc uplifting completely. However, `x test --stage 2` on CI still currently builds a stage3 rustc for some reason, and if we removed uplifting completely, even for non-cross-compiled builds, that would cause an additional rustc build, and that's not great. So for now let's just allow uplifting for non-cross-compiled builds.
Fixesrust-lang/rust#145534.
r? `@jieyouxu`
Remove unused `PartialOrd`/`Ord` from bootstrap
It was just wasting compile-time. There is one remaining "old" bootstrap test that uses the `Ord` impl on one test step, I'll remove that later.
Trace some basic I/O operations in bootstrap
When working on removing the rmeta sysroot copies, it is quite difficult to figure out *why* was did a certain file appear in a given directory. This should help with that a bit.
r? `@jieyouxu`
Do not strip binaries in bootstrap everytime if they are unchanged
I was profiling bootstrap to figure out why a no-op build takes upward of two seconds on my machine. I found that half of that is Cargo (which is mostly unavoidable) and the rest (~900ms) is running strip. We don't need to restrip already stripped binaries all the time.
r? `@jieyouxu`
Improve context of bootstrap errors in CI
Inspired by https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/printing.20test.20suite.20name.20by.20default/with/534920583, this PR attempts to improve the context displayed when a bootstrap invocation fails in CI.
Since https://github.com/rust-lang/rust/pull/145261, we now see the latest started step when a failure occurs. However, we can go further.
1) The first commit prints the actual executed bootstrap invocation command arguments when bootstrap ends. Since CI jobs often run multiple bootstrap commands, this makes it easier to figure out which one of them failed (before it was annoying having to search for that in CI logs). Because bootstrap doesn't really use `Result`s much, and most of them time it ends with the `detail_exit` function, which YOLOs `std::process::exit(...)`, I added the print there.
2) Adds `#[track_caller]` to a few bootstrap Cargo builder functions. This makes the log that we print when a command fails more accurate:
```
2025-08-16T18:18:51.6998201Z Command ... failed ...
2025-08-16T18:18:51.7003653Z Created at: src/bootstrap/src/core/builder/cargo.rs:423:33
2025-08-16T18:18:51.7004032Z Executed at: src/bootstrap/src/core/build_steps/doc.rs:933:26
```
Before, the `cargo.rs:XYZ` location wasn't very useful.
3) Is the most wild thing (I'll revert if you find it too magical). We store the step stack of the currently active `Builder` instance in a global variable, and when bootstrap exits with a failure, we print the stack, to make it easier to find out what was happening when a failure occurred. We could print an actual captured `Backtrace`, but I think that would be too much information in the common case. We now pass `RUST_BACKTRACE=1` on CI, so if bootstrap actually crashes unexpectedly, we would see the stacktrace.
The end of the bootsrap failure log in CI now looks like this now:
```
Bootstrap failed while executing `x build library`
---BOOTSTRAP step stack start---
Assemble { target_compiler: Compiler { stage: 1, host: x86_64-unknown-linux-gnu, forced_compiler: false } }
Rustc { target: x86_64-unknown-linux-gnu, build_compiler: Compiler { stage: 0, host: x86_64-unknown-linux-gnu, forced_compiler: false }, crates: [] }
---BOOTSTRAP step stack end---
```
r? `@jieyouxu`
Do not copy .rmeta files into the sysroot of the build compiler during check of rustc/std
Before, when bootstrap did a check build of rustc stage N (with a build compiler that was stage N-1), it automatically copied the resulting `.rmeta` artifacts into the sysroot of the stage N-1 build compiler, so that stage N `rustc_private` tools such as `miri` could be compiled using the stage N-1 build compiler. This has a number of issues:
- It was done unconditionally, even if no `rustc_private` tools were actually built.
- If we did a check and a build of the same stage compiler in the same bootstrap invocation, the generated rmeta and rlib files could clash. This is also why you can see that `check::Std` actually doesn't copy the artifacts anymore (which forced us to build std instead of just checking it in a bunch of `Check` steps).
- It was polluting the sysroot of the build compiler. This is especially annoying for the stage 0 compiler, because we are forced to create an artificial sysroot for it, so that we can copy new stuff into it.
- It was very implicit in bootstrap.
Based on suggestions by ```@cuviper``` and ```@bjorn3,``` I tried to change how this behaves. Instead of copying the rmeta artifacts into the sysroot of the build compiler (from where they would be loaded implicitly), they are now stored in a separate transient bootstrap build directory, and they are then explicitly passed *only* when checking `rustc_private` tools using the `-L` flag. The flags are passed out-of-band through our rustc wrapper, to avoid invalidating the build cache. This is the first commit.
The second commit does the same for std. For a few months, we used to build std instead of just checking it when doing a cross-compile check of something that required std, this now fixes it. There is still the previous ordering requirement though, that `check::Std` has to be executed as the last check step, or rather nothing that requires checked std should be executed *after* it, because it will run into rmeta/rlib duplications (4fa90ef799/src/bootstrap/src/core/builder/mod.rs (L1066)). I tried to fix in this PR, but it quickly runs into the fact that building things currently copies *rlib* artifacts into the build compiler sysroot. I want to fix that as one of the next steps. After we get rid of all the copies (or rather, we only do the copies for dist/stage2+ and do not copy anything into the stage0 compiler's sysroot), we could hopefully finally get rid of `stage0-sysroot`.
Based on my local tests, this seems to be working fine. If it works on CI, and we don't run into other issues after merging it, I'd like to do the same also for rlib artifacts generated during `x build`.
r? ```@jieyouxu```
Do not copy files in `copy_src_dirs` in dry run
This reduces the time to run the current 9 dist snapshot tests from ~24s to ~2s on my PC.
r? `@jieyouxu`
Fix tracing debug representation of steps without arguments in bootstrap
I was wondering why I see `lainSourceTarbal` in tracing logs...
r? `@jieyouxu`
Remove duplicated tracing span in bootstrap
`trace_cmd` is now called also in the `stream` method, so including it also here was duplicating command spans.
r? `@jieyouxu`
bootstrap: Reduce dependencies
Eliminate the `fd-lock` dependency by using the new native locking in std.
Eliminate the `xattr` dependency by turning off a feature flag in `tar`, since
the tarballs that we extract with bootstrap don't need it.
Split codegen backend check step into two and don't run it with `x check compiler`
This reduces the amount of work that is done during `x check compiler`. We still check both backends during `x check` by defaut, even if they are not in `rust.codegen-backends`, as just checking them shouldn't require expensive preparations, like building GCC.
r? `@jieyouxu`
bootstrap: Fix jemalloc 64K page support for aarch64 tools
Resolvesrust-lang/rust#133748
The prior page size fix only targeted the compile build step, not the tools step: https://github.com/rust-lang/rust/pull/135081
Also note that since `miri` always uses jemalloc, I didn't copy the `builder.config.jemalloc(target)` check to the tools section.
Tested by running `strings` on the compiled `miri` binary to see the LG_PAGE value.
Before:
```
> strings miri | grep '^LG_PAGE'
LG_PAGE 14
```
After:
```
> strings miri | grep '^LG_PAGE'
LG_PAGE 16
```
May also need a separate fix for the standalone miri repository: https://github.com/rust-lang/miri/issues/4514 (likely a change needed in miri-script?)
Rename and document `ONLY_HOSTS` in bootstrap
Everytime I examined the `ONLY_HOSTS` flag of bootstrap steps, I was utterly confused. Why is it called ONLY_HOSTS? How does the fact that it is skipped if `--target` is passed, but `--host` is not (which was not accurate) help me?
The reality of the flag is that if it is true, the targets for which the given Step will be built is determined based on the `--host` flag, while if it is false, it is determined based on the `--target` flag, that's pretty much it. The previous comment was just a (not very helpful and not even accurate) corollary of that.
I clarified the comment, and also renamed the flag to `IS_HOST` (happy to brainstorm better names, but the doc. comment change is IMO the main improvement).
r? ``@jieyouxu``
Improve tracing in bootstrap
I was annoyed that bootstrap had like 5 separate ways of debugging/tracing/profiling, and it was hard for me to understand how are individual steps executed. This PR tries to unify severla things behind `BOOTSTRAP_TRACING`, and improve tracing/profiling in general:
- All generated tracing outputs are now stored in a single directory to make it easier to examine them, plus bootstrap prepares a `latest` symlink to the latest generated tracing output directory for convenience.
- All executed spans are now logged automatically (without requiring usage of `#[tracing::instrument]`).
- A custom span/event formatter was implemented, to provide domain-specific output (like location of executed commands or spans) and hopefully also to reduce visual clutter.
- `tracing_forest` was removed. While it did some useful postprocessing, it didn't expose enough information for making the dynamic step spans work.
- You can now explicitly log steps (`STEP=info`) and/or commands (`COMMAND=info`), to have more granular control over what gets logged.
- `print-step-timings` also show when a step starts its execution (not just when it ends it), so that when some step fails in CI, we can actually see what step it was (before we would only see the end of the previous step).
- The rustc-dev-guide page on debugging/profiling bootstrap was updated.
There are still some things that work outside of tracing (`print-step-timings` and `dump-bootstrap-shims`), but I think that for now this improvement is good enough.
I removed the `> step`, `< step` verbose output, because I found it unusable, as verbose bootstrap output also enables verbose Cargo output, and then you simply drown in too much data, and because I think that the new tracing system makes it obsolete (although it does require recompilation with the `tracing` feature). If you want to keep it, happy to revert 690c781475. And the information about cached steps is now also shown in the Graphviz step dependency graph.
We can modify the tracing output however we want, as we now implement it ourselves. Notably, we could also show exit logs for step spans, currently I only show enter spans. Maybe creating indents for each executed nested command is also not needed. Happy to hear feedback!
Some further improvements could be to print step durations, if we decide to also log step exit events. We could also try to enable tracing in CI logs, but it might be too verbose.
Best reviewed commit-by-commit.
r? ``@jieyouxu``
CC ``@Shourya742``
Enforce in bootstrap that clippy must have stage at least 1
This mostly piggybacks on the previous `x check` [rework](https://github.com/rust-lang/rust/pull/143048).
The new "rules" follow the new staging logic. So `x clippy <foo>` lints `foo` using stage0 Clippy. `x clippy --stage 2 <foo>` lints `foo` using stage1 Clippy (which is built from in-tree sources).
I had to fix some latent issues with `prepare_compiler_for_check` along the way.
Checking `rustc_private` tools should now check less compiler crates (or rather not check compiler examples/tests/etc.), potentially speeding it up slightly.
I also had to make some manual adjustments to `x clippy ci` so that it doesn't do needless work.
r? `@jieyouxu`
