tailscale/tool/gocross/gocross-wrapper.sh
David Anderson bfe5623a86 tool/gocross: make gocross behave with pre-release Go toolchains
Also switch the wrapper script to use bash not posix shell. We now
depend on bash elsewhere for saner behavior in esoteric areas, so
might as well use it everywhere for consistency.

Fixes #8425

Signed-off-by: David Anderson <danderson@tailscale.com>
2023-06-23 13:57:05 -07:00

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#!/usr/bin/env bash
# Copyright (c) Tailscale Inc & AUTHORS
# SPDX-License-Identifier: BSD-3-Clause
#
# gocross-wrapper.sh is a wrapper that can be aliased to 'go', which
# transparently builds gocross using a "bootstrap" Go toolchain, and
# then invokes gocross.
set -euo pipefail
if [[ "${CI:-}" == "true" ]]; then
set -x
fi
# Locate a bootstrap toolchain and (re)build gocross if necessary. We run all of
# this in a subshell because posix shell semantics make it very easy to
# accidentally mutate the input environment that will get passed to gocross at
# the bottom of this script.
(
repo_root="${BASH_SOURCE%/*}/../.."
# Figuring out if gocross needs a rebuild, as well as the rebuild itself, need
# to happen with CWD inside this repo. Since we're in a subshell entirely
# dedicated to wrangling gocross and toolchains, cd over now before doing
# anything further so that the rest of this logic works the same if gocross is
# being invoked from somewhere else.
cd "$repo_root"
toolchain="$HOME/.cache/tailscale-go"
if [[ -d "$toolchain" ]]; then
# A toolchain exists, but is it recent enough to compile gocross? If not,
# wipe it out so that the next if block fetches a usable one.
want_go_minor=$(grep -E '^go ' "go.mod" | cut -f2 -d'.')
have_go_minor=$(head -1 "$toolchain/VERSION" | cut -f2 -d'.')
# Shortly before stable releases, we run release candidate
# toolchains, which have a non-numeric suffix on the version
# number. Remove the rc qualifier, we just care about the minor
# version.
have_go_minor="${have_go_minor%rc*}"
if [[ -z "$have_go_minor" || "$have_go_minor" -lt "$want_go_minor" ]]; then
rm -rf "$toolchain" "$toolchain.extracted"
fi
fi
if [[ ! -d "$toolchain" ]]; then
mkdir -p "$HOME/.cache"
# We need any Go toolchain to build gocross, but the toolchain also has to
# be reasonably recent because we upgrade eagerly and gocross might not
# build with Go N-1. So, if we have no cached tailscale toolchain at all,
# fetch the initial one in shell. Once gocross is built, it'll manage
# updates.
read -r REV <go.toolchain.rev
case "$REV" in
/*)
toolchain="$REV"
;;
*)
# This works for linux and darwin, which is sufficient
# (we do not build tailscale-go for other targets).
HOST_OS=$(uname -s | tr A-Z a-z)
HOST_ARCH="$(uname -m)"
if [[ "$HOST_ARCH" == "aarch64" ]]; then
# Go uses the name "arm64".
HOST_ARCH="arm64"
elif [[ "$HOST_ARCH" == "x86_64" ]]; then
# Go uses the name "amd64".
HOST_ARCH="amd64"
fi
rm -rf "$toolchain" "$toolchain.extracted"
curl -f -L -o "$toolchain.tar.gz" "https://github.com/tailscale/go/releases/download/build-${REV}/${HOST_OS}-${HOST_ARCH}.tar.gz"
mkdir -p "$toolchain"
(cd "$toolchain" && tar --strip-components=1 -xf "$toolchain.tar.gz")
echo "$REV" >"$toolchain.extracted"
rm -f "$toolchain.tar.gz"
;;
esac
fi
# Binaries run with `gocross run` can reinvoke gocross, resulting in a
# potentially fancy build that invokes external linkers, might be
# cross-building for other targets, and so forth. In one hilarious
# case, cmd/cloner invokes go with GO111MODULE=off at some stage.
#
# Anyway, build gocross in a stripped down universe.
gocross_path="gocross"
gocross_ok=0
wantver="$(git rev-parse HEAD)"
if [[ -x "$gocross_path" ]]; then
gotver="$($gocross_path gocross-version 2>/dev/null || echo '')"
if [[ "$gotver" == "$wantver" ]]; then
gocross_ok=1
fi
fi
if [[ "$gocross_ok" == "0" ]]; then
unset GOOS
unset GOARCH
unset GO111MODULE
unset GOROOT
export CGO_ENABLED=0
"$toolchain/bin/go" build -o "$gocross_path" -ldflags "-X tailscale.com/version.gitCommitStamp=$wantver" tailscale.com/tool/gocross
fi
) # End of the subshell execution.
exec "${BASH_SOURCE%/*}/../../gocross" "$@"