Add host.runner for wrapping host build target executions by nitsky · Pull Request #16599 · rust-lang/cargo

nitsky · 2026-02-06T19:14:26Z

What does this PR try to resolve?

This PR resolves #16591 by adding support for host.runner config under the existing -Zhost-config unstable feature. Cargo already has target.<triple>.runner to wrap execution of target binaries (cargo run/test/bench), but no equivalent for host build targets like build scripts.

How to test and review this PR?

The implementation is two small changes in compilation.rs:

target_runner() now uses bcx.target_data.target_config(kind).runner instead of manually constructing a target.{triple}.runner key, mirroring how target_linker() already works. This routes through host_config for CompileKind::Host when -Zhost-config is enabled.
host_process() now prepends the runner, mirroring the existing logic in target_process().

I added four new tests to cover the feature.

rustbot · 2026-02-06T19:14:31Z

r? @epage

rustbot has assigned @epage.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

Owners of files modified in this PR: @ehuss, @epage, @weihanglo
@ehuss, @epage, @weihanglo expanded to ehuss, epage, weihanglo
Random selection from ehuss, epage, weihanglo

weihanglo

Thanks for the contribution. Looks pretty complete!

View changes since this review

weihanglo · 2026-02-08T14:44:35Z

tests/testsuite/build_script.rs

I understand the the failure already show that it is working, could we have a successful case using the echo_wrapper? Such as having this WRAPPER CALLED: snapshot

cargo/tests/testsuite/build.rs

Lines 4464 to 4474 in b9f0d83

let p = project().file("src/lib.rs", "").build();

let wrapper = tools::echo_wrapper();

p.cargo("build -v")

.env("RUSTC_WRAPPER", &wrapper)

.with_stderr_data(str![[r#"

[COMPILING] foo v0.0.1 ([ROOT]/foo)

[RUNNING] `[..]/rustc-echo-wrapper[EXE] rustc --crate-name foo [..]`

WRAPPER CALLED: rustc --crate-name foo [..]

[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s

"#]])

I added a commit to handle this.

weihanglo

Thanks!

View changes since this review

nitsky · 2026-02-08T15:46:43Z

@weihanglo any idea why this failed on windows x86_64?

weihanglo · 2026-02-09T07:50:24Z

@weihanglo any idea why this failed on windows x86_64?

I guess due to raw string so backlashes in Windows paths were not escaped. Perhaps we can instead use CARGO_HOST_RUNNER=<value> to avoid escaping?

… scripts)

nitsky · 2026-02-09T16:22:28Z

@weihanglo fixed, ready for merge?

nitsky · 2026-02-09T16:22:36Z

@weihanglo fixed, ready for merge?

weihanglo

Thanks!

View changes since this review

Update cargo submodule 27 commits in fe2f314aef06e688a9517da1ac0577bb1854d01f..0c9e687d237ff04b53ccb67b4ce63e9483789e88 2026-01-30 21:52:01 +0000 to 2026-02-11 05:58:30 +0000 - chore: downgrade to libc@0.2.180 (rust-lang/cargo#16624) - fix(script): Load config relative to the script (rust-lang/cargo#16620) - fix(lints): Don't run on-by-default lints when MSRV is too old (rust-lang/cargo#16618) - fix(build): Remove deprecated, unstable --out-dir (rust-lang/cargo#16608) - fix(script): Make the lockfile script-specific independent of build-dir (rust-lang/cargo#16619) - fix(lockfile-path): Respect the config in fix, install (rust-lang/cargo#16617) - chore: upgrade to gix@0.79.0 (rust-lang/cargo#16615) - chore: downgrade to libc@0.2.179 (rust-lang/cargo#16613) - feat(timings): Enable text selection in the charts (rust-lang/cargo#16607) - Add host.runner for wrapping host build target executions (rust-lang/cargo#16599) - feat(schema): Add `impl Copy for RustVersion` (rust-lang/cargo#16609) - refactor(lints): Cleanup (rust-lang/cargo#16610) - refactor(timings): Remove `CanvasRenderer` in favor of `SvgRenderer` (rust-lang/cargo#16602) - Fix known hosts parsing (rust-lang/cargo#16596) - chore: pin openssl-src to 300.5.4 (rust-lang/cargo#16601) - chore(deps): bump time from 0.3.46 to 0.3.47 (rust-lang/cargo#16593) - feat(lints): Add missing_lints_inheritance (rust-lang/cargo#16588) - chore(deps): bump git2 from 0.20.3 to 0.20.4 (rust-lang/cargo#16589) - chore(deps): update msrv (3 versions) to v1.91 (rust-lang/cargo#16587) - feat(lints): Add unused_workspace_package_fields lint (rust-lang/cargo#16585) - Add command field to BuildStarted in build-analysis (rust-lang/cargo#16577) - Fix link for lockfile-publish-time (rust-lang/cargo#16582) - docs(cli): Discuss commands and aliases (rust-lang/cargo#16581) - fix(script): Correct style of help message (rust-lang/cargo#16580) - chore(deps): update compatible (rust-lang/cargo#16578) - chore(deps): update crate-ci/typos action to v1.42.3 (rust-lang/cargo#16579) - fix(timings): Only compute `y_ticks` when the `units` is not empty. (rust-lang/cargo#16575)

This is a regression found in rust-lang/compiler-builtins#1087 and introduced by rust-lang#16599 There are other regression that `host.runner` and `host.linker` are accidentally applied to target builds which I plan to fix both in a follow-up PR. (rust-lang#12535 introduced the `host.linker` bug btw)

This is a regression found in rust-lang/miri#4855 and introduced by rust-lang#16599 There are other regression that `host.runner` and `host.linker` are accidentally applied to target builds which I plan to fix both in a follow-up PR. (rust-lang#12535 introduced the `host.linker` bug btw)

### What does this PR try to resolve? This is a regression found in rust-lang/compiler-builtins#1087 and introduced by #16599 There are other regression that `host.runner` and `host.linker` are accidentally applied to target builds which I plan to fix both in a follow-up PR. (#12535 introduced the `host.linker` bug btw)

briansmith · 2026-02-12T19:47:44Z

There seems to be a lot of fallout from this PR or related changes. It seems like there isn't enough testing of when the CARGO_TARGET_<target>_RUNNER and related settings are supposed to and not supposed to be applied, as the implementation of this feature seems notably different than what was described in the related issue, issue #16591. I think it should be reverted, the intended semantics better documented, and then more tests written to cover the intended semantics.

Update cargo submodule 27 commits in fe2f314aef06e688a9517da1ac0577bb1854d01f..0c9e687d237ff04b53ccb67b4ce63e9483789e88 2026-01-30 21:52:01 +0000 to 2026-02-11 05:58:30 +0000 - chore: downgrade to libc@0.2.180 (rust-lang/cargo#16624) - fix(script): Load config relative to the script (rust-lang/cargo#16620) - fix(lints): Don't run on-by-default lints when MSRV is too old (rust-lang/cargo#16618) - fix(build): Remove deprecated, unstable --out-dir (rust-lang/cargo#16608) - fix(script): Make the lockfile script-specific independent of build-dir (rust-lang/cargo#16619) - fix(lockfile-path): Respect the config in fix, install (rust-lang/cargo#16617) - chore: upgrade to gix@0.79.0 (rust-lang/cargo#16615) - chore: downgrade to libc@0.2.179 (rust-lang/cargo#16613) - feat(timings): Enable text selection in the charts (rust-lang/cargo#16607) - Add host.runner for wrapping host build target executions (rust-lang/cargo#16599) - feat(schema): Add `impl Copy for RustVersion` (rust-lang/cargo#16609) - refactor(lints): Cleanup (rust-lang/cargo#16610) - refactor(timings): Remove `CanvasRenderer` in favor of `SvgRenderer` (rust-lang/cargo#16602) - Fix known hosts parsing (rust-lang/cargo#16596) - chore: pin openssl-src to 300.5.4 (rust-lang/cargo#16601) - chore(deps): bump time from 0.3.46 to 0.3.47 (rust-lang/cargo#16593) - feat(lints): Add missing_lints_inheritance (rust-lang/cargo#16588) - chore(deps): bump git2 from 0.20.3 to 0.20.4 (rust-lang/cargo#16589) - chore(deps): update msrv (3 versions) to v1.91 (rust-lang/cargo#16587) - feat(lints): Add unused_workspace_package_fields lint (rust-lang/cargo#16585) - Add command field to BuildStarted in build-analysis (rust-lang/cargo#16577) - Fix link for lockfile-publish-time (rust-lang/cargo#16582) - docs(cli): Discuss commands and aliases (rust-lang/cargo#16581) - fix(script): Correct style of help message (rust-lang/cargo#16580) - chore(deps): update compatible (rust-lang/cargo#16578) - chore(deps): update crate-ci/typos action to v1.42.3 (rust-lang/cargo#16579) - fix(timings): Only compute `y_ticks` when the `units` is not empty. (rust-lang/cargo#16575)

rustbot assigned epage Feb 6, 2026

rustbot added A-build-execution Area: anything dealing with executing the compiler A-documenting-cargo-itself Area: Cargo's documentation S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 6, 2026

weihanglo reviewed Feb 8, 2026

View reviewed changes

weihanglo approved these changes Feb 8, 2026

View reviewed changes

weihanglo enabled auto-merge February 8, 2026 15:13

auto-merge was automatically disabled February 9, 2026 15:41
Head branch was pushed to by a user without write access

Add host.runner for wrapping host build target executions (e.g. build…

e5f4609

… scripts)

nitsky force-pushed the host-runner branch from 3d0791e to e5f4609 Compare February 9, 2026 15:41

weihanglo approved these changes Feb 9, 2026

View reviewed changes

weihanglo added this pull request to the merge queue Feb 9, 2026

Merged via the queue into rust-lang:master with commit 8b251d9 Feb 9, 2026
29 checks passed

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Feb 9, 2026

This was referenced Feb 10, 2026

Tracking Issue for host-config #9452

Open

Update cargo submodule rust-lang/rust#152240

Merged

Copilot AI mentioned this pull request Feb 11, 2026

Document rustc/cargo incompatibility blocking cfg parsing (nightly-2026-02-07) flux-rs/flux#1478

Closed

rustbot added this to the 1.95.0 milestone Feb 11, 2026

weihanglo mentioned this pull request Feb 12, 2026

fix: apply host.runner only when host-config enabled #16631

Merged

andygrove mentioned this pull request Feb 12, 2026

Miri CI broken by nightly-2026-02-12 regression in cargo apache/datafusion-comet#3499

Closed

briansmith mentioned this pull request Feb 12, 2026

Regression: CARGO_TARGET_<triple>_RUNNER used for build scripts #16634

Closed

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Add host.runner for wrapping host build target executions#16599

Add host.runner for wrapping host build target executions#16599
weihanglo merged 1 commit intorust-lang:masterfrom
tangramdotdev:host-runner

nitsky commented Feb 6, 2026

Uh oh!

rustbot commented Feb 6, 2026

Uh oh!

weihanglo left a comment •

edited by rustbot

Loading

Uh oh!

weihanglo Feb 8, 2026

Uh oh!

nitsky Feb 8, 2026

Uh oh!

weihanglo left a comment •

edited by rustbot

Loading

Uh oh!

nitsky commented Feb 8, 2026

Uh oh!

weihanglo commented Feb 9, 2026

Uh oh!

nitsky commented Feb 9, 2026

Uh oh!

nitsky commented Feb 9, 2026

Uh oh!

weihanglo left a comment •

edited by rustbot

Loading

Uh oh!

Uh oh!

briansmith commented Feb 12, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

	let p = project().file("src/lib.rs", "").build();
	let wrapper = tools::echo_wrapper();
	p.cargo("build -v")
	.env("RUSTC_WRAPPER", &wrapper)
	.with_stderr_data(str![[r#"
	[COMPILING] foo v0.0.1 ([ROOT]/foo)
	[RUNNING] `[..]/rustc-echo-wrapper[EXE] rustc --crate-name foo [..]`
	WRAPPER CALLED: rustc --crate-name foo [..]
	[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s

	"#]])

Conversation

nitsky commented Feb 6, 2026

What does this PR try to resolve?

How to test and review this PR?

Uh oh!

rustbot commented Feb 6, 2026

Uh oh!

weihanglo left a comment • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

weihanglo Feb 8, 2026

Choose a reason for hiding this comment

Uh oh!

nitsky Feb 8, 2026

Choose a reason for hiding this comment

Uh oh!

weihanglo left a comment • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

nitsky commented Feb 8, 2026

Uh oh!

weihanglo commented Feb 9, 2026

Uh oh!

nitsky commented Feb 9, 2026

Uh oh!

nitsky commented Feb 9, 2026

Uh oh!

weihanglo left a comment • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

briansmith commented Feb 12, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

weihanglo left a comment •

edited by rustbot

Loading

weihanglo left a comment •

edited by rustbot

Loading

weihanglo left a comment •

edited by rustbot

Loading