Reject running `compiletest` self-tests against stage 0 rustc unless explicitly allowed #144675

jieyouxu · 2025-07-30T08:45:12Z

Currently, in pr-check-1, we run python3 ../x.py test --stage 0 src/tools/compiletest, which is compiletest self-tests against stage 0 rustc. This makes it very annoying for PRs wanting to change target spec JSON format, which compiletest depends on for target information, as otherwise compiletest would have to know how to handle 2 different target spec JSON formats and know when to pick which.

Instead of doing that, we change compiletest self-tests to reject running against stage 0 rustc unless explicitly allowed with build.compiletest-allow-stage0=true. build.compiletest-allow-stage0 is a proper bootstrap config option in favor of the ad-hoc COMPILETEST_FORCE_STAGE0 env var. This means that:

./x test src/tools/compiletest --stage=0 is not allowed, unless build.compiletest-allow-stage0=true is set. In this scenario, compiletest self-tests should be expected to fail unless the stage 0 rustc as provided is like codegen_cranelift where it's actually built from in-tree rustc sources.
In CI, we change ./x test src/tools/compiletest --stage=0 to ./x test src/tools/compiletest --stage=1, and move it to pr-check-2. Yes, this involves building the stage 1 compiler, but pr-check-2 already has to build stage 1 compiler to test stage 1 library crates.
Crucially, this means that compiletest is only intended to support one target spec JSON format, namely the one corresponding to the in-tree rustc.
This should preserve the compiletest-use-stage0-libtest UX optimization where changing compiler/ tree should still not require rebuilding compiletest as long as build.compiletest-use-stage0-libtest=true, as that should remain orthogonal. This is completely unlike my previous attempt at Consider compiletest a staged ToolStd tool #144563 that tries to do a way more invasive change which would cause the rebuild problem.

Best reviewed commit-by-commit.

r? @Kobzol

jieyouxu · 2025-07-30T08:46:29Z

cc @bjorn3 on the cg_clif changes (commit 2 mostly)

rustbot · 2025-07-30T08:46:35Z

This PR modifies bootstrap.example.toml.

If appropriate, please update CONFIG_CHANGE_HISTORY in src/bootstrap/src/utils/change_tracker.rs.

This PR modifies src/bootstrap/src/core/config.

If appropriate, please update CONFIG_CHANGE_HISTORY in src/bootstrap/src/utils/change_tracker.rs.

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh

jieyouxu · 2025-07-30T09:01:14Z

0 checks

Hello?

Kobzol

opt-dist and cg_gcc will also need to be updated (you can grep for usage of COMPILETEST_FORCE_STAGE0).

bootstrap.example.toml

rustbot · 2025-07-30T11:15:28Z

Some changes occurred in compiler/rustc_codegen_gcc

cc @antoyo, @GuillaumeGomez

Some changes occurred in src/tools/opt-dist

cc @Kobzol

jieyouxu · 2025-07-30T11:27:07Z

Changes since last review:

Also updated cg_gcc and opt-dist (I forgor).
Updated comment re. intended use case.

jieyouxu · 2025-07-30T11:47:32Z

@rustbot author

In favor of the adhoc `COMPILETEST_FORCE_STAGE0` env var.

…test-allow-stage0`

…explicitly allowed Otherwise, `compiletest` would have to know e.g. how to parse two different target spec, if target spec format was changed between beta `rustc` and in-tree `rustc`.

And move `./x test compiletest --stage=1` to `pr-check-2`, where testing library artifacts already requires building the stage 1 compiler.

jieyouxu · 2025-07-30T12:45:19Z

@rustbot review

Kobzol · 2025-07-30T13:12:05Z

Thanks!

@bors r+

bors · 2025-07-30T13:12:09Z

📌 Commit e954253 has been approved by Kobzol

It is now in the queue for this repository.

Rollup of 4 pull requests Successful merges: - #143465 (Support multiple crate versions in --extern-html-root-url) - #144308 ([rustdoc] Display total time and compilation time of merged doctests) - #144655 (clean up codegen fn attrs) - #144675 (Reject running `compiletest` self-tests against stage 0 rustc unless explicitly allowed) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #144675 - jieyouxu:compiletest-staging, r=Kobzol Reject running `compiletest` self-tests against stage 0 rustc unless explicitly allowed Currently, in `pr-check-1`, we run `python3 ../x.py test --stage 0 src/tools/compiletest`, which is `compiletest` self-tests against stage 0 rustc. This makes it very annoying for PRs wanting to change target spec JSON format, which `compiletest` depends on for target information, as otherwise `compiletest` would have to know how to handle 2 different target spec JSON formats and know when to pick which. Instead of doing that, we change `compiletest` self-tests to reject running against stage 0 `rustc` *unless* explicitly allowed with `build.compiletest-allow-stage0=true`. `build.compiletest-allow-stage0` is a proper bootstrap config option in favor of the ad-hoc `COMPILETEST_FORCE_STAGE0` env var. This means that: - `./x test src/tools/compiletest --stage=0` is not allowed, unless `build.compiletest-allow-stage0=true` is set. In this scenario, `compiletest` self-tests should be expected to fail unless the stage 0 `rustc` as provided is like codegen_cranelift where it's *actually* built from in-tree `rustc` sources. - In CI, we change `./x test src/tools/compiletest --stage=0` to `./x test src/tools/compiletest --stage=1`, and move it to `pr-check-2`. Yes, this involves building the stage 1 compiler, but `pr-check-2` already has to build stage 1 compiler to test stage 1 library crates. - Crucially, this means that **`compiletest` is only intended to support one target spec JSON format**, namely the one corresponding to the in-tree `rustc`. - This should preserve the `compiletest-use-stage0-libtest` UX optimization where changing `compiler/` tree should still not require rebuilding `compiletest` as long as `build.compiletest-use-stage0-libtest=true`, as that should remain orthogonal. This is completely unlike my previous attempt at #144563 that tries to do a way more invasive change which would cause the rebuild problem. Best reviewed commit-by-commit. --- r? `@Kobzol`

…Kobzol Properly pass path to staged `rustc` to `compiletest` self-tests Otherwise, this can do weird things like use a global rustc, or try to use stage 0 rustc. This must be properly configured, because `compiletest` is intended to only support one compiler target spec JSON format (of the in-tree compiler). Historically, this was probably done so before `bootstrap` was really its own thing, and `compiletest` had to be runnable as a much more "self-standing" tool. Follow-up to rust-lang#144675, as I didn't realize this until Zalathar pointed it out in [#t-infra/bootstrap > Building vs testing &rust-lang#96;compiletest&rust-lang#96; @ 💬](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Building.20vs.20testing.20.60compiletest.60/near/532040838). r? `@Kobzol`

…Kobzol Properly pass path to staged `rustc` to `compiletest` self-tests Otherwise, this can do weird things like use a global rustc, or try to use stage 0 rustc. This must be properly configured, because `compiletest` is intended to only support one compiler target spec JSON format (of the in-tree compiler). Historically, this was probably done so before `bootstrap` was really its own thing, and `compiletest` had to be runnable as a much more "self-standing" tool. Follow-up to rust-lang#144675, as I didn't realize this until Zalathar pointed it out in [#t-infra/bootstrap > Building vs testing &rust-lang#96;compiletest&rust-lang#96; @ 💬](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Building.20vs.20testing.20.60compiletest.60/near/532040838). r? ``@Kobzol``

…Kobzol Properly pass path to staged `rustc` to `compiletest` self-tests Otherwise, this can do weird things like use a global rustc, or try to use stage 0 rustc. This must be properly configured, because `compiletest` is intended to only support one compiler target spec JSON format (of the in-tree compiler). Historically, this was probably done so before `bootstrap` was really its own thing, and `compiletest` had to be runnable as a much more "self-standing" tool. Follow-up to rust-lang#144675, as I didn't realize this until Zalathar pointed it out in [#t-infra/bootstrap > Building vs testing &rust-lang#96;compiletest&rust-lang#96; @ 💬](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Building.20vs.20testing.20.60compiletest.60/near/532040838). r? ```@Kobzol```

…Kobzol Properly pass path to staged `rustc` to `compiletest` self-tests Otherwise, this can do weird things like use a global rustc, or try to use stage 0 rustc. This must be properly configured, because `compiletest` is intended to only support one compiler target spec JSON format (of the in-tree compiler). Historically, this was probably done so before `bootstrap` was really its own thing, and `compiletest` had to be runnable as a much more "self-standing" tool. Follow-up to rust-lang#144675, as I didn't realize this until Zalathar pointed it out in [#t-infra/bootstrap > Building vs testing &rust-lang#96;compiletest&rust-lang#96; @ 💬](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Building.20vs.20testing.20.60compiletest.60/near/532040838). r? ````@Kobzol````

rustbot assigned Kobzol Jul 30, 2025

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jieyouxu changed the title ~~Reject running compiletest self-tests against stage 0 rustc unless forced~~ Reject running compiletest self-tests against stage 0 rustc unless explicitly allowed Jul 30, 2025

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jieyouxu added 5 commits July 30, 2025 19:54

Introduce proper build.compiletest-allow-stage0 config option

0cf6eb5

In favor of the adhoc `COMPILETEST_FORCE_STAGE0` env var.

Update codegen_{cranelift,gcc} and opt-dist to use `build.compile…

a7fcc73

…test-allow-stage0`

Deny compiletest self-tests being run against stage 0 rustc unless …

2033a06

…explicitly allowed Otherwise, `compiletest` would have to know e.g. how to parse two different target spec, if target spec format was changed between beta `rustc` and in-tree `rustc`.

Run compiletest self-tests against stage 1 rustc

2cdd193

And move `./x test compiletest --stage=1` to `pr-check-2`, where testing library artifacts already requires building the stage 1 compiler.

Add change tracker entry

e954253

jieyouxu force-pushed the compiletest-staging branch from 274e067 to e954253 Compare July 30, 2025 11:55

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samueltardieu mentioned this pull request Jul 30, 2025

Rollup of 4 pull requests #144692

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bors merged commit 202d1f5 into rust-lang:master Jul 30, 2025
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Make target pointer width in target json an integer #144443

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Reject running `compiletest` self-tests against stage 0 rustc unless explicitly allowed #144675

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