Commits on Apr 19, 2016

1. 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 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

   

   alexcrichton committed Apr 19, 2016
   Configuration menu

   • View commit details
   • Copy full SHA for 02538d4
   • Browse repository at this point

   Copy the full SHA

   02538d4 View commit details

   Browse the repository at this point in the history