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Add `x86_64-unikraft-linux-musl` target This introduces `x86_64-unikraft-linux-musl` as the first Rust target for the [Unikraft] Unikernel Development Kit. [Unikraft]: https://unikraft.org/ Unikraft imitates Linux and uses musl as libc. It is extremely configurable, and does not even provide a `poll` implementation or a network stack, unless enabled by the end user who compiles the application. Our approach for integrating the build process with `rustc` is to hide the build process as well as the actual final linking step behind a linker-shim (`kraftld`, see https://github.com/unikraft/kraftkit/issues/612). ## 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.) I will be the target maintainer. > - 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 `x86_64-unikraft-linux-musl` was derived from `x86_64-unknown-linux-musl`, setting Unikraft as vendor. Unikraft exactly imitates Linux + musl. > - 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. No dependencies were added to Rust. Requirements for linking are [Unikraft] and [KraftKit] (both BSD-3-Clause), but none of these are added to Rust. [KraftKit]: https://github.com/unikraft/kraftkit > - 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. Understood. I am not a member of a Rust team. > - 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. Understood. `std` is supported. > - 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. Building is described in the platform support doc. It will be updated once proper `kraftld` support has landed. > - 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. Understood. > - 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. I don't think this PR breaks anything. r? compiler-team |
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| README.md | ||
rustc_target contains some very low-level details that are
specific to different compilation targets and so forth.
For more information about how rustc works, see the rustc dev guide.