Dockerfile

FROM golang:1.18.2-bullseye

RUN set -eux; \
	apt-get update; \
	apt-get install -y --no-install-recommends \
		arch-test \
		file \
		patch \
	; \
	rm -rf /var/lib/apt/lists/*

# https://github.com/golang/go/issues/56426
RUN set -eux; \
	wget -O /tmp/go-mips.patch 'https://github.com/golang/go/commit/2c7c98c3ad719aa9d6d2594827a6894ff9950042.patch'; \
	patch --strip=1 --directory=/usr/local/go --input=/tmp/go-mips.patch

# note: we cannot add "-s" here because then "govulncheck" does not work (see SECURITY.md); the ~0.2MiB increase (as of 2022-12-16, Go 1.18) is worth it
ENV BUILD_FLAGS="-v -trimpath -ldflags '-d -w'"

RUN set -eux; \
	{ \
		echo '#!/usr/bin/env bash'; \
		echo 'set -Eeuo pipefail -x'; \
		echo 'eval "go build $BUILD_FLAGS -o /go/bin/gosu-$ARCH"'; \
		echo 'file "/go/bin/gosu-$ARCH"'; \
		echo 'if arch-test "$ARCH"; then'; \
# there's a fun QEMU + Go 1.18+ bug that causes our binaries (especially on ARM arches) to hang indefinitely *sometimes*, hence the "timeout" and looping here
		echo '  try() { for (( i = 0; i < 30; i++ )); do if timeout 1s "$@"; then return 0; fi; done; return 1; }'; \
		echo '  try "/go/bin/gosu-$ARCH" --version'; \
		echo '  try "/go/bin/gosu-$ARCH" nobody id'; \
		echo '  try "/go/bin/gosu-$ARCH" nobody ls -l /proc/self/fd'; \
		echo 'fi'; \
	} > /usr/local/bin/gosu-build-and-test.sh; \
	chmod +x /usr/local/bin/gosu-build-and-test.sh

# disable CGO for ALL THE THINGS (to help ensure no libc)
ENV CGO_ENABLED 0

WORKDIR /go/src/github.com/tianon/gosu

COPY go.mod go.sum ./
RUN set -eux; \
	go mod download; \
	go mod verify

COPY *.go ./

# gosu-$(dpkg --print-architecture)
RUN ARCH=amd64    GOARCH=amd64       gosu-build-and-test.sh
RUN ARCH=i386     GOARCH=386         gosu-build-and-test.sh
RUN ARCH=armel    GOARCH=arm GOARM=5 gosu-build-and-test.sh
RUN ARCH=armhf    GOARCH=arm GOARM=6 gosu-build-and-test.sh
#RUN ARCH=armhf    GOARCH=arm GOARM=7 gosu-build-and-test.sh # boo Raspberry Pi, making life hard (armhf-is-v7 vs armhf-is-v6 ...)
RUN ARCH=arm64    GOARCH=arm64       gosu-build-and-test.sh
RUN ARCH=mips64el GOARCH=mips64le    gosu-build-and-test.sh
RUN ARCH=ppc64el  GOARCH=ppc64le     gosu-build-and-test.sh
RUN ARCH=riscv64  GOARCH=riscv64     gosu-build-and-test.sh
RUN ARCH=s390x    GOARCH=s390x       gosu-build-and-test.sh

RUN set -eux; ls -lAFh /go/bin/gosu-*; file /go/bin/gosu-*