This is a mostly routine update, with some edits for a benchmark API
change.
I'm not updating LLVM here, since that could conflict with other ongoing
work.
- Update bazel to 8.3.1, just to stay reasonably up to date.
- Bazel warned about the platforms version, so I generally updated
packages that have central registry versions.
- Note there's a newer re2 in the central registry, but I got a download
error with it.
- `--experimental_guard_against_concurrent_changes` is deprecated; I
wasn't sure it's worth explicitly setting
`--guard_against_concurrent_changes=full`, but figured it may be
consistent (it's not clear to me -- see
https://github.com/bazelbuild/bazel/pull/25874).
- Updates incompatible flags.
- `rules_flex` is no longer used, so enable its flag.
- Fixes `sh_test` deps for
`--incompatible_disable_autoloads_in_main_repo`
- Broadens the exception for `rules_cc` and `bazel_tools` due to changes
to runfiles deps; trying to avoid minutiae that shouldn't affect the
decision.
This updates to bazel 8.0.0, also updating bazel mod deps and tools to
make that function. The release is a couple weeks old, and we haven't
updated in a while, and it's a major release. Note it includes some
incompatible flag flips that this is trying to update with respect to.
I'll try generally enabling incompatible support separately.
The most visible bazel behavior change here will be the change from `~`
to `+` in repo path names. (If you're curious,
https://github.com/bazelbuild/bazel/issues/23127 indicates this fixes a
Windows performance issue)
Note that this is building on top of both the action env update in #4728
(which got me started down this path) and the proto removal in #4731
(which would add significant work to this update). Only the commit
starting at "Work towards bazel 8.0.0" is specifically part of this PR.
The only documentation I can find for `.bazelversion` is in
https://github.com/bazelbuild/bazelisk/blob/master/README.md. However,
`bazel` will error out if it doesn't match the `.bazelversion`. For
example:
```
╚╡/usr/bin/bazel build :all
ERROR: The project you're trying to build requires Bazel 7.3.0 (specified in [elided]/carbon-lang/.bazelversion), but it wasn't found in /usr/bin.
```
Switching to this because the `MODULE.bazel` requires tighter version
pinning in order to avoid churn, and this should help catch mistakes
early.
In `MODULE.bazel`, demote mention of the version issue because it should
only really occur now when the version is being deliberately changed, so
the connection should be more apparent.
We switched to the released version to minimize rebuildds of the
toolchain, but with downloading the toolchain this isn't a significant
issue any more. And without this, Bazel doesn't run on ARM macOS.
This may hit issues with broken Bazel builds and have to be reverted.
Added a TODO to reverse this as soon as we can anyways.
Also cleans up the old `.bazelversion` in favor of just using
`.bazeliskrc`. They both work, but the RC file comes first in the
sequence so happy to prefer it here.
Per chandlerc's comment:
First, this builds inside the Bazel tree rather than in the source
repository. This ensures we start in a clean directory each time the
repository rule is run again. We don't need to detect an existing build
with this, and it will only be rebuilt when the workspace file or the
repository rule implementation is changed. This can be forced by using:
```
bazel sync --configure
```
Second, we use an implicit dependency on the `WORKSPACE` file to locate
the workspace directory automatically, and the `HEAD` file from the
`llvm-project` submodule to trigger a rebuild if the submodule is
updated.
Third, teach the CMake script to try to use a system-installed `clang`
if installed and not overridden by the `CC` environment variable. This
is very different from the prior logic -- this is only used with the
CMake build, and so should work with any system C++ compiler that can
build Clang and LLVM.
Lastly, this tweaks the CMake options to tune this build given that we
now fully control it and it will only be used in this context. This
still results in a 1.5gb build for me. =/ But its as small as I can make
it really. It's a frustrating long list, but I couldn't find a more
brief way of representing this.
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
The Bazel bits are collected into a directory and given less confusing
names (I hope). Other than names, everything is a direct copy from the
toolchain repository without any edits.
A few files needed to be merged in:
- `.gitignore`
- `.pre-commit-config.yaml`
Subsequent commits will add relevant C++ infrastructure and then the
source code itself.
Chandler Carruth
Jon Ross-Perkins
Jon MeowandChandler Carruth