We already know which headers are necessary, so it's wasteful to put the
full zig_sdk to every sandbox.
This reduces the number of files in `external/zig_sdk` from 15k to 4k or
6k, depending on the action.
The slowness of bazel-zig-cc comes from setup and teardown of sandbox
directories[1]. Turning on `experimental_reuse_sandbox_directories`
speeds it up significantly.
Depending on how the tests with this go in the next few days, I will add
this recommendation to README.
This has been marked as safe to use and no longer experimental as of
Bazel master[2].
[1]: https://git.sr.ht/~motiejus/test-zigcc
[2]: https://github.com/bazelbuild/bazel/pull/16490
Just like we know the path to zig_lib_dir, we do know the path to
zig_exe. Lets use that.
This was surfaced by experimenting with
`--experimental_use_hermetic_linux_sandbox`.
`repository_ctx.path("zig")` would return the real file system path to
zig (outside of the sandbox), which is not good when the sandbox is
hermetic.
Co-developed-by: Fabian Hahn <fabian@hahn.graphics>
Cache reuse in zig is currently quite fragile (we are using a forked
version with github.com/ziglang/zig/issues/13051), so ensure that it
does not regress when zig SDK upgrades.
Previously the toolchain wrappers used to assume the zig_lib_dir is
always in "lib". However, it depends on the OS: macos-x86_64 and
linux-aarch64 have it in "lib/zig".
Update the wrapper scripts to reflect that.
Zig does not always share `libc++.a` and the glibc shims. We have observed
to be caused for 2 reasons:
- For some commands Go `chdir`s to `/tmp/`. This causes `ZIG_LIB_DIR` to be
absolute, which blows the cache key to find the right `libc++.a` (because Zig
thinks we are using a different lib dir to compile libc++). This is currently
worked around in `toolchain/defs.bzl` by overfitting to Go and returning
early from that particular invocation.
- Sometimes Bazel's sandbox messes up Zig's cache keys. If one runs without the
sandbox (`--spawn_strategy=standalone`), the cache hit rate and thus the
build time are much better.
This is actively investigated. I am adding `--spawn_strategy=standalone`
to CI to see the speedup that it provides. I will rollback it later.
Go ignores CFLAGS for some commands. That causes unnecessary build of
glibc shims (and libc++.a).
In the GCC days cross-compiler toolchains used to expose a "tool" per
architecture. Let's do the same here. Then Go cannot cheat with skipping
CFLAGS which we normally *always* expect.
The wrapper code is getting gnarly, I know. But it still fits in my head
somehow, so we can still keep adding to it.
'common' is not a thing in Windows; but it needs to be defined.
This makes v1.0.0-rc3 broken for Windows, and not useful (yet) for
anyone else but me. Revert the README update too.
