Ship LLVM tools for the correct target when cross-compiling
The LLVM config returned from the `Llvm` step in bootstrap was always the *host* LLVM config (as we cannot execute the cross-compiled LLVM config). But this wasn't obvious in bootstrap before (there was just a comment about it, but that's it), which caused a bug where bootstrap was copying LLVM tools from the host target to the cross-compiled rustc sysroot. This was probably happening for quite a long time, we just haven't noticed before.
Note that I consider this to be mostly a hotfix, I plan to refactor the LLVM handling in bootstrap soon-ish to make it harder to misuse and be better in general.
Fixes: https://github.com/rust-lang/rust/issues/145699
Add aarch64_be-unknown-hermit target
Follow-up to rust-lang/rust#144962, which added the target necessary to build the Hermit bootloader and kernel for `aarch64_be`. This adds the target for Rust applications that can run in Hermit.
I've been testing this for a while now and `@mkroening` and `@stlankes` are on board with adding this target.
About the [tier 3 target policy](https://doc.rust-lang.org/rustc/target-tier-policy.html#tier-3-target-policy):
> - A tier 3 target must have a designated developer or developers (the "target maintainers") on record to be CCed when issues arise regarding the target. (The mechanism to track and CC such developers may evolve over time.)
The maintainers for this target are the same as for the other Hermit targets, `@mkroening` and `@stlankes.`
> - Targets must use naming consistent with any existing targets; for instance, a target for the same CPU or OS as an existing Rust target should use the same name for that CPU or OS. Targets should normally use the same names and naming conventions as used elsewhere in the broader ecosystem beyond Rust (such as in other toolchains), unless they have a very good reason to diverge. Changing the name of a target can be highly disruptive, especially once the target reaches a higher tier, so getting the name right is important even for a tier 3 target.
> - Target names should not introduce undue confusion or ambiguity unless absolutely necessary to maintain ecosystem compatibility. For example, if the name of the target makes people extremely likely to form incorrect beliefs about what it targets, the name should be changed or augmented to disambiguate it.
> - If possible, use only letters, numbers, dashes and underscores for the name. Periods (.) are known to cause issues in Cargo.
The target name is consistent with the existing `aarch64-unknown-hermit` target and the existing big endian aarch64 targets like `aarch64_be-unknown-linux-gnu`.
> - Tier 3 targets may have unusual requirements to build or use, but must not create legal issues or impose onerous legal terms for the Rust project or for Rust developers or users.
> - The target must not introduce license incompatibilities.
> - Anything added to the Rust repository must be under the standard Rust license (MIT OR Apache-2.0).
> - The target must not cause the Rust tools or libraries built for any other host (even when supporting cross-compilation to the target) to depend on any new dependency less permissive than the Rust licensing policy. This applies whether the dependency is a Rust crate that would require adding new license exceptions (as specified by the tidy tool in the rust-lang/rust repository), or whether the dependency is a native library or binary. In other words, the introduction of the target must not cause a user installing or running a version of Rust or the Rust tools to be subject to any new license requirements.
> - Compiling, linking, and emitting functional binaries, libraries, or other code for the target (whether hosted on the target itself or cross-compiling from another target) must not depend on proprietary (non-FOSS) libraries. Host tools built for the target itself may depend on the ordinary runtime libraries supplied by the platform and commonly used by other applications built for the target, but those libraries must not be required for code generation for the target; cross-compilation to the target must not require such libraries at all. For instance, rustc built for the target may depend on a common proprietary C runtime library or console output library, but must not depend on a proprietary code generation library or code optimization library. Rust's license permits such combinations, but the Rust project has no interest in maintaining such combinations within the scope of Rust itself, even at tier 3.
> - "onerous" here is an intentionally subjective term. At a minimum, "onerous" legal/licensing terms include but are not limited to: non-disclosure requirements, non-compete requirements, contributor license agreements (CLAs) or equivalent, "non-commercial"/"research-only"/etc terms, requirements conditional on the employer or employment of any particular Rust developers, revocable terms, any requirements that create liability for the Rust project or its developers or users, or any requirements that adversely affect the livelihood or prospects of the Rust project or its developers or users.
There are no licensing issues or proprietary components required to compile for this target.
> - Neither this policy nor any decisions made regarding targets shall create any binding agreement or estoppel by any party. If any member of an approving Rust team serves as one of the maintainers of a target, or has any legal or employment requirement (explicit or implicit) that might affect their decisions regarding a target, they must recuse themselves from any approval decisions regarding the target's tier status, though they may otherwise participate in discussions.
> - This requirement does not prevent part or all of this policy from being cited in an explicit contract or work agreement (e.g. to implement or maintain support for a target). This requirement exists to ensure that a developer or team responsible for reviewing and approving a target does not face any legal threats or obligations that would prevent them from freely exercising their judgment in such approval, even if such judgment involves subjective matters or goes beyond the letter of these requirements.
Ack.
> - Tier 3 targets should attempt to implement as much of the standard libraries as possible and appropriate (core for most targets, alloc for targets that can support dynamic memory allocation, std for targets with an operating system or equivalent layer of system-provided functionality), but may leave some code unimplemented (either unavailable or stubbed out as appropriate), whether because the target makes it impossible to implement or challenging to implement. The authors of pull requests are not obligated to avoid calling any portions of the standard library on the basis of a tier 3 target not implementing those portions.
This target implements std with the same featureset as `aarch64-unknown-hermit`.
> - The target must provide documentation for the Rust community explaining how to build for the target, using cross-compilation if possible. If the target supports running binaries, or running tests (even if they do not pass), the documentation must explain how to run such binaries or tests for the target, using emulation if possible or dedicated hardware if necessary.
Ack, that is part of the markdown document.
> - Tier 3 targets must not impose burden on the authors of pull requests, or other developers in the community, to maintain the target. In particular, do not post comments (automated or manual) on a PR that derail or suggest a block on the PR based on a tier 3 target. Do not send automated messages or notifications (via any medium, including via `@)` to a PR author or others involved with a PR regarding a tier 3 target, unless they have opted into such messages.
> - Backlinks such as those generated by the issue/PR tracker when linking to an issue or PR are not considered a violation of this policy, within reason. However, such messages (even on a separate repository) must not generate notifications to anyone involved with a PR who has not requested such notifications.
Ack.
> - Patches adding or updating tier 3 targets must not break any existing tier 2 or tier 1 target, and must not knowingly break another tier 3 target without approval of either the compiler team or the maintainers of the other tier 3 target.
> - In particular, this may come up when working on closely related targets, such as variations of the same architecture with different features. Avoid introducing unconditional uses of features that another variation of the target may not have; use conditional compilation or runtime detection, as appropriate, to let each target run code supported by that target.
This doesn't break any existing targets.
> - Tier 3 targets must be able to produce assembly using at least one of rustc's supported backends from any host target. (Having support in a fork of the backend is not sufficient, it must be upstream.)
The LLVM backend works.
> - If a tier 3 target stops meeting these requirements, or the target maintainers no longer have interest or time, or the target shows no signs of activity and has not built for some time, or removing the target would improve the quality of the Rust codebase, we may post a PR to remove it; any such PR will be CCed to the target maintainers (and potentially other people who have previously worked on the target), to check potential interest in improving the situation.
Ack.
r? compiler_leads
Fix host code appearing in Wasm binaries
This is a direct fix for issue [132802](https://github.com/rust-lang/rust/issues/132802).
Followed the outline as follows:
> * give a hard error in bootstrap when using gcc to compile for wasm
> * change our CI to use clang instead of gcc
> * add a test that compiling a sample program for wasm32-unknown doesn't give any linker warnings
The `test-various` ci job was also changed.
try-job: test-various
try-job: dist-various-1
try-job: dist-various-2
try-job: x86_64-msvc-1
Remove default config from bootstrap
This PR removes the default config initialization from parse_inner, as it introduced many assumptions during config setup. Instead, each variable is now manually initialized to eliminate certain invariants in parse_inner and streamline the process.
r? `@Kobzol`
Download CI GCC into the correct directory
While doing various experiments with stage3 cross-compilations, I realized that bootstrap is unable to download LLVM from CI for a non-host target, which is quite annoying. Fixing this for LLVM will take some work, but in the meantime we can easily fix this for `download-ci-gcc`, which was implemented in a much more self-contained way.
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```
