run

#!/usr/bin/env bash
set -euo pipefail

# https://github.com/ziglang/zig/wiki/Contributing

script_dir=$(cd "${BASH_SOURCE[0]%/*}" && pwd)
args=("$@")

#―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
# Env vars that affect this script

# Path to the Zig source repo
src=${src:-/tmp/zig-src}

# Path to the build directory
build_dir=${build_dir:-/tmp/zig-build}

#―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
# All build/test functions in this script place the local zig-cache inside
# $build_dir to avoid cluttering $src.
#
# All build functions are idempotent.

#―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

# Build Zig from source, using only a C compiler
#
# The resulting binary is located at $build_dir/stage3/bin/zig
buildBootstrap() {
    prepareBuild

    ninja install

    fixDynamicLinking "$build_dir/stage3/bin/zig"
}

# As a faster alternative to `buildBootstrap`, fetch a prebuilt Zig stage3 binary
usePrebuilt() {
    # This creates $build_dir/config.h, required for building Zig
    prepareBuild
    # This creates $build_dir/zigcpp/libzigcpp.a, required for building Zig
    ninja zigcpp

    nix build "$script_dir"#zigPrebuiltNoLib -o "$build_dir/helper/stage3-prebuilt"
    # Copy instead of symlinking so that the Zig binary automatically picks up
    # the Zig lib dir and `config.h` in $build_dir
    install -D -T --compare "$build_dir/helper/stage3-prebuilt/zig" "$build_dir/stage3/bin/zig"
}

prepareBuild() {
    mkdir -p "$build_dir/helper"

    enterDevEnv

    cd "$build_dir"
    export ZIG_LOCAL_CACHE_DIR=$build_dir/zig-cache
    cmake "$src" -DCMAKE_BUILD_TYPE=Release -DZIG_NO_LIB=ON -GNinja

    # Required due to -DZIG_NO_LIB=ON, so that zig can find the stdlib
    ln -sfn "$src/lib" "$build_dir/lib"
}

# - Set the correct dynamic linker (glibc's ld-linux) from the dev env.
#   Zig uses the linker used in /usr/bin/env, which can have the wrong version.
# - Add glibc to the RPATH.
#   This is not needed for the dynamic linker to load the correct glibc version
#   (because the linker uses the glibc directory in which the linker itself is located).
#   But it fixes "wrong version" warnings for glibc in tools like `ldd`, which only use
#   resources like RPATH for resolving shared libraries.
fixDynamicLinking() {
    binary=$1
    patchelf --shrink-rpath \
             "$binary"
    patchelf --set-interpreter "$(cat "$NIX_BINTOOLS/nix-support/dynamic-linker")" \
             --add-rpath "$(cat "$NIX_BINTOOLS/nix-support/orig-libc")/lib" \
             "$binary"
}

#―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
# Build Zig from source, using the the Zig binary built in `buildBootstrap`.

buildDebug() {
    build zig-debug "$@"
}

buildRelease() {
    build zig-release -Doptimize=ReleaseFast -Dstrip "$@"
}

build() {
    prefix=$1
    shift

    if [[ ! -e "$build_dir/stage3/bin/zig" ]]; then
        echo '`stage3/bin/zig` does not exist. Run one of the following:'
        echo 'run buildBootstrap'
        echo 'run usePrebuilt'
    fi

    enterDevEnv

    cd $src

    printAndRun "$build_dir"/stage3/bin/zig build --prefix "$build_dir/$prefix" \
                --cache-dir "$build_dir/zig-cache" -Denable-llvm -Dno-lib "$@"

    fixDynamicLinking "$build_dir/$prefix/bin/zig"
}

#―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

testStdlib() {
    zigSrc build test-std -Dskip-release -Dskip-non-native "$@"
}

# Run stdlib tests just for the native CPU
testStdlibFast() {
    zigSrc test lib/std/std.zig --zig-lib-dir lib --main-mod-path lib/std "$@"
}

# Basic compiler tests
testBehavior() {
    zigSrc build test-behavior -Dskip-non-native "$@"
}

# Basic compiler tests, running just the default Debug configuration
testBehaviorFast() {
    zigSrc test test/behavior.zig -I test
}

zigSrc() {
    cd $src
    zigDebug "$@"
}

zigDebug() {
    local cmd=$1
    shift
    printAndRun "$build_dir/zig-debug/bin/zig" "$cmd" --cache-dir "$build_dir/zig-cache" "$@"
}

#―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
dev_env=$build_dir/helper/dev-env.sh
dev_env_profile=$build_dir/helper/dev-env-profile
dev_env_src_hash_file=$build_dir/helper/dev-env-src-hash

# Run this script in the Nix dev env
enterDevEnv() {
    if [[ ${inZigDevEnv:-} == 1 ]]; then return; fi

    src_hash=$(cd $script_dir; sha256sum zig.nix outputs.nix flake.lock)
    if [[ ! -e $dev_env || $src_hash != $(cat "$dev_env_src_hash_file" 2>/dev/null || :) ]]; then
        # Create dev env

        # Cleanup profile links to only save a gcroot to the latest dev env
        rm -f "$dev_env_profile"-*-link

        mkdir -p "$build_dir/helper"

        # Create dev env and save it in a profile to prevent garbage collection. This
        # is important so that dynamic libraries linked by Zig don't disappear.
        # Use sed to remove `NIX_BUILD_TOP` and tmpdir aliases to `NIX_BUILD_TOP`, so that no
        # tmpdir is created each time the the dev env is sourced.
        nix print-dev-env --profile "$dev_env_profile" "$script_dir" |
            sed -E '/^export (NIX_BUILD_TOP=|\S+=.*?NIX_BUILD_TOP)/d' > "$dev_env"

        echo "$src_hash" > "$dev_env_src_hash_file"
    fi

    # Source dev env file instead of calling `nix develop`:
    # - With warm caches and a clean Flake dir, this is 10x faster than `nix develop`.
    #   `nix develop` introduces a slight but noticeable delay.
    # - `nix develop` always evaluates `nixpkgs#bashInteractive`.
    #    This forces a download of nixpkgs (and a reevaluation of `bashInteractive`) after
    #    `tarball-ttl` (default: 1 h) which adds an unacceptable delay of many seconds.
    . "$dev_env"
    exec "${BASH_SOURCE[0]}" "${args[@]}"
}

# Eval a cmd in the dev env
cmd() {
    enterDevEnv
    eval "$@"
}

printAndRun() {
    printf "%q " "$@"; echo
    eval "$@"
}

#―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

case ${1:-} in
    ''|h|help|-h|--help)
        echo "See ./$(realpath --relative-to="$PWD" "$script_dir/usage.sh") for usage"
        echo
        echo "Info:"
        echo "src:"
        echo "$src"
        echo
        echo "build_dir:"
        echo "$build_dir"
        exit
        ;;
esac

eval "$@"