hermetic_cc_toolchain/toolchain/defs.bzl

load("@bazel_skylib//lib:shell.bzl", "shell")
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
load("@bazel_tools//tools/build_defs/repo:utils.bzl", "read_user_netrc", "use_netrc")
load("@bazel-zig-cc//toolchain/private:defs.bzl", "DEFAULT_INCLUDE_DIRECTORIES", "ZIG_TOOL_PATH", "target_structs")

_fcntl_map = """
GLIBC_2.2.5 {
   fcntl;
};
"""
_fcntl_h = """
#ifdef __ASSEMBLER__
.symver fcntl64, fcntl@GLIBC_2.2.5
#else
__asm__(".symver fcntl64, fcntl@GLIBC_2.2.5");
#endif
"""

# Official recommended version. Should use this when we have a usable release.
URL_FORMAT_RELEASE = "https://ziglang.org/download/{version}/zig-{host_platform}-{version}.tar.xz"

# Caution: nightly releases are purged from ziglang.org after ~90 days. A real
# solution would be to allow the downstream project specify their own mirrors.
# This is explained in
# https://sr.ht/~motiejus/bazel-zig-cc/#alternative-download-urls and is
# awaiting my attention or your contribution.
URL_FORMAT_NIGHTLY = "https://ziglang.org/builds/zig-{host_platform}-{version}.tar.xz"

# Author's mirror that doesn't purge the nightlies so aggressively. I will be
# cleaning those up manually only after the artifacts are not in use for many
# months in bazel-zig-cc. dl.jakstys.lt is a small x86_64 server with an NVMe
# drive sitting in my home closet on a 1GB/s symmetric residential connection,
# which, as of writing, has been quite reliable.
URL_FORMAT_JAKSTYS = "https://dl.jakstys.lt/zig/zig-{host_platform}-{version}.tar.xz"

_VERSION = "0.10.0-dev.1393+291f5055f"

_HOST_PLATFORM_SHA256 = {
    "linux-aarch64": "10c6618f57f6253c047098aee4093fe36e7fc4da7f0ed2451cca91e8b84575b8",
    "linux-x86_64": "de30008c98ba61791ab5caa78ec9fbe20c76f8e57c7a41e1cf5788d8f59b4c7e",
    "macos-aarch64": "72edc26973d697bba68f138701ebf9755548677ecedd853fd224baa836bef2f8",
    "macos-x86_64": "78220a4460a7c0f563d7365313fcd3ea028ed38166ebac55ba22f17ab6404851",
}

def register_toolchains(
        register = [],
        version = _VERSION,
        url_formats = [URL_FORMAT_JAKSTYS],
        host_platform_sha256 = _HOST_PLATFORM_SHA256):
    """
        Download zig toolchain and register some.
        @param register registers the given toolchains to the system using
        native.register_toolchains(). See README for possible choices.
    """
    zig_repository(
        name = "zig_sdk",
        version = version,
        url_formats = url_formats,
        host_platform_sha256 = host_platform_sha256,
        host_platform_include_root = {
            "linux-aarch64": "lib/",
            "linux-x86_64": "lib/",
            "macos-aarch64": "lib/zig/",
            "macos-x86_64": "lib/zig/",
        },
    )

    toolchains = ["@zig_sdk//toolchain:%s" % t for t in register]
    native.register_toolchains(*toolchains)

ZIG_TOOL_WRAPPER = """#!/bin/bash
set -e

if [[ -n "$TMPDIR" ]]; then
  _cache_prefix=$TMPDIR
else
  _cache_prefix="$HOME/.cache"
  if [[ "$(uname)" = Darwin ]]; then
    _cache_prefix="$HOME/Library/Caches"
  fi
fi
export ZIG_LOCAL_CACHE_DIR="$_cache_prefix/bazel-zig-cc"
export ZIG_GLOBAL_CACHE_DIR=$ZIG_LOCAL_CACHE_DIR

exec "{zig}" "{zig_tool}" "$@"
"""

_ZIG_TOOLS = [
    "c++",
    "cc",
    "ar",
    "ld.lld",  # ELF
    "ld64.lld",  # Mach-O
    "lld-link",  # COFF
    "wasm-ld",  # WebAssembly
]

def _zig_repository_impl(repository_ctx):
    arch = repository_ctx.os.arch
    if arch == "amd64":
        arch = "x86_64"

    os = repository_ctx.os.name.lower()
    if os.startswith("mac os"):
        os = "macos"

    host_platform = "{}-{}".format(os, arch)

    zig_include_root = repository_ctx.attr.host_platform_include_root[host_platform]
    zig_sha256 = repository_ctx.attr.host_platform_sha256[host_platform]
    format_vars = {
        "version": repository_ctx.attr.version,
        "host_platform": host_platform,
    }

    urls = [uf.format(**format_vars) for uf in repository_ctx.attr.url_formats]
    repository_ctx.download_and_extract(
        auth = use_netrc(read_user_netrc(repository_ctx), urls, {}),
        url = urls,
        stripPrefix = "zig-{host_platform}-{version}/".format(**format_vars),
        sha256 = zig_sha256,
    )

    for zig_tool in _ZIG_TOOLS:
        repository_ctx.file(
            ZIG_TOOL_PATH.format(zig_tool = zig_tool),
            ZIG_TOOL_WRAPPER.format(
                zig = str(repository_ctx.path("zig")),
                zig_tool = zig_tool,
            ),
        )

    repository_ctx.file(
        "glibc-hacks/fcntl.map",
        content = _fcntl_map,
    )
    repository_ctx.file(
        "glibc-hacks/glibchack-fcntl.h",
        content = _fcntl_h,
    )

    repository_ctx.symlink(
        Label("//toolchain/platform:BUILD"),
        "platform/BUILD",
    )

    repository_ctx.template(
        "BUILD",
        Label("//toolchain:BUILD.sdk.bazel"),
        executable = False,
        substitutions = {
            "{zig_include_root}": shell.quote(zig_include_root),
        },
    )

    repository_ctx.symlink(
        Label("//toolchain/toolchain:BUILD"),
        "toolchain/BUILD",
    )

    repository_ctx.template(
        "private/BUILD",
        Label("//toolchain/private:BUILD.sdk.bazel"),
        executable = False,
        substitutions = {
            "{absolute_path}": shell.quote(str(repository_ctx.path(""))),
            "{zig_include_root}": shell.quote(zig_include_root),
        },
    )

zig_repository = repository_rule(
    attrs = {
        "version": attr.string(),
        "host_platform_sha256": attr.string_dict(),
        "url_formats": attr.string_list(allow_empty = False),
        "host_platform_include_root": attr.string_dict(),
    },
    implementation = _zig_repository_impl,
)

def filegroup(name, **kwargs):
    native.filegroup(name = name, **kwargs)
    return ":" + name

def declare_files(zig_include_root):
    filegroup(name = "empty")
    native.exports_files(["zig"], visibility = ["//visibility:public"])
    filegroup(name = "lib/std", srcs = native.glob(["lib/std/**"]))

    lazy_filegroups = {}

    for target_config in target_structs():
        for d in DEFAULT_INCLUDE_DIRECTORIES + target_config.includes:
            d = zig_include_root + d
            if d not in lazy_filegroups:
                lazy_filegroups[d] = filegroup(name = d, srcs = native.glob([d + "/**"]))