tailscale/tool/gocross/gocross-wrapper.sh
David Anderson d27a6e1c53 tool/gocross: fix incorrect relpath usage in bootstrap script
The subshell in which gocross gets built cd's to the corp checkout dir
near the top, so all future references to corp repository files should
be simple relative paths, and not reference $repo_root. When $repo_root
is an absolute path, it doesn't matter and everything works out, but on
some OSes and shells and invocations, $repo_root is a completely relative
path that is invalidated by the "cd".

Fixes tailscale/corp#11183

Signed-off-by: David Anderson <danderson@tailscale.com>
2023-05-09 16:19:46 -07:00

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#!/usr/bin/env sh
# 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 -eu
if [ "${CI:-}" = "true" ]; then
set -x
fi
# Locate a bootstrap toolchain and (re)build gocross if necessary. We run all of
# this in a subshell because posix shell semantics make it very easy to
# accidentally mutate the input environment that will get passed to gocross at
# the bottom of this script.
(
repo_root="$(dirname $0)/../.."
# Figuring out if gocross needs a rebuild, as well as the rebuild itself, need
# to happen with CWD inside this repo. Since we're in a subshell entirely
# dedicated to wrangling gocross and toolchains, cd over now before doing
# anything further so that the rest of this logic works the same if gocross is
# being invoked from somewhere else.
cd "$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=$(grep -E '^go ' "go.mod" | cut -f2 -d'.')
have_go_minor=$(cut -f2 -d'.' <$toolchain/VERSION)
if [ -z "$have_go_minor" -o "$have_go_minor" -lt "$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 "$(dirname $0)/../../gocross" "$@"