Bootstrapping unstable code from a stable compiler #29557
Comments
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@eddyb may have some ideas abut this |
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If distros don't have anything against multiple packages, they can generate, e.g. Otherwise, we could put an "unlocked" rustc in Then our build system can look for a compatible |
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If we just relax the bootstrap key a little, and make it a statically-known value instead of a "secret", then there would be no need for wrapper scripts. The build system could just export that value applicable to stage0 invocations too. As the configure script says itself, that secret is just meant to be a mild deterrent. By default it's only a A statically-known bootstrap key is not that different from an unlocked Aside, it might be nice if the resulting |
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Would this include cross-compiling |
This commit removes all infrastructure from the repository for our so-called snapshots to instead bootstrap the compiler from stable releases. Bootstrapping from a previously stable release is a long-desired feature of distros because they're not fans of downloading binary stage0 blobs from us. Additionally, this makes our own CI easier as we can decommission all of the snapshot builders and start having a regular cadence to when we update the stage0 compiler. A new `src/etc/get-stage0.py` script was added which shares some code with `src/bootstrap/bootstrap.py` to read a new file, `src/stage0.txt`, which lists the current stage0 compiler as well as cargo that we bootstrap from. This script will download the relevant `rustc` package an unpack it into `$target/stage0` as we do today. One problem of bootstrapping from stable releases is that we're not able to compile unstable code (e.g. all the `#![feature]` directives in libcore/libstd). To overcome this we employ two strategies: * The bootstrap key of the previous compiler is hardcoded into `src/stage0.txt` (enabled as a result of rust-lang#32731) and exported by the build system. This enables nightly features in the compiler we download. * The standard library and compiler are pinned to a specific stage0, which doesn't change, so we're guaranteed that we'll continue compiling as we start from a known fixed source. The process for making a release will also need to be tweaked now to continue to cadence of bootstrapping from the previous release. This process looks like: 1. Merge `beta` to `stable` 2. Produce a new stable compiler. 3. Change `master` to bootstrap from this new stable compiler. 4. Merge `master` to `beta` 5. Produce a new beta compiler 6. Change `master` to bootstrap from this new beta compiler. Step 3 above should involve very few changes as `master` was previously bootstrapping from `beta` which is the same as `stable` at that point in time. Step 6, however, is where we benefit from removing lots of `#[cfg(stage0)]` and get to use new features. This also shouldn't slow the release too much as steps 1-5 requires little work other than waiting and step 6 just needs to happen at some point during a release cycle, it's not time sensitive. Closes rust-lang#29555 Closes rust-lang#29557
mk: Bootstrap from stable instead of snapshots This commit removes all infrastructure from the repository for our so-called snapshots to instead bootstrap the compiler from stable releases. Bootstrapping from a previously stable release is a long-desired feature of distros because they're not fans of downloading binary stage0 blobs from us. Additionally, this makes our own CI easier as we can decommission all of the snapshot builders and start having a regular cadence to when we update the stage0 compiler. A new `src/etc/get-stage0.py` script was added which shares some code with `src/bootstrap/bootstrap.py` to read a new file, `src/stage0.txt`, which lists the current stage0 compiler as well as cargo that we bootstrap from. This script will download the relevant `rustc` package an unpack it into `$target/stage0` as we do today. One problem of bootstrapping from stable releases is that we're not able to compile unstable code (e.g. all the `#![feature]` directives in libcore/libstd). To overcome this we employ two strategies: * The bootstrap key of the previous compiler is hardcoded into `src/stage0.txt` (enabled as a result of #32731) and exported by the build system. This enables nightly features in the compiler we download. * The standard library and compiler are pinned to a specific stage0, which doesn't change, so we're guaranteed that we'll continue compiling as we start from a known fixed source. The process for making a release will also need to be tweaked now to continue to cadence of bootstrapping from the previous release. This process looks like: 1. Merge `beta` to `stable` 2. Produce a new stable compiler. 3. Change `master` to bootstrap from this new stable compiler. 4. Merge `master` to `beta` 5. Produce a new beta compiler 6. Change `master` to bootstrap from this new beta compiler. Step 3 above should involve very few changes as `master` was previously bootstrapping from `beta` which is the same as `stable` at that point in time. Step 6, however, is where we benefit from removing lots of `#[cfg(stage0)]` and get to use new features. This also shouldn't slow the release too much as steps 1-5 requires little work other than waiting and step 6 just needs to happen at some point during a release cycle, it's not time sensitive. Closes #29555 Closes #29557
The stable Rust compiler requires the nightly Rust compiler to build. This is no good for distros that want to bootstrap from their own toolchain and don't want to maintain a nightly toolchain just for building Rust. We'll teach the Rust makefiles to deal with bootstrapping off the stable compiler transparently (the stable compiler already contains nightly features, just inaccessible).
https://internals.rust-lang.org/t/perfecting-rust-packaging-the-plan/2767
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