Support building on an arm64 host too

This adds a `.host-arch` symlink to build output; this doesn't get committed (for hopefully obvious reasons), but allows for things like `CMD` and `update.sh` to have a known-effective target for testing the output further in some way.

This was a mapping we already had thanks to `ARCH_TEST`, so I've also reordered our builds such that they're grouped by "host" architecture and sorted by "preference"/compatibility (with the goal that we get a more "correct" `.host-arch` symlink).

Author: tianon-sso

.dockerignore

@@ -4,5 +4,6 @@
 *.sh
 .dockerignore
 .git*
+.host-arch
 Dockerfile*
 LICENSE

.gitignore

@@ -0,0 +1 @@
+.host-arch

Dockerfile.build

@@ -3,6 +3,7 @@ FROM debian:bookworm-slim
 
 RUN set -eux; \
 	apt-get update; \
+	dpkgArch="$(dpkg --print-architecture)"; \
 	apt-get install -y --no-install-recommends \
 		ca-certificates \
 		gnupg \
@@ -12,6 +13,8 @@ RUN set -eux; \
 		libc6-dev \
 		make \
 		\
+# these are all "arch:all" so we can just install all of them
+		libc6-dev-amd64-cross \
 		libc6-dev-arm64-cross \
 		libc6-dev-armel-cross \
 		libc6-dev-armhf-cross \
@@ -21,7 +24,9 @@ RUN set -eux; \
 		libc6-dev-riscv64-cross \
 		libc6-dev-s390x-cross \
 		\
-		gcc-aarch64-linux-gnu \
+# the cross-compilers are particular about which architectures they build for, so for now we'll only support a host architecture of amd64 or arm64
+		$([ "$dpkgArch" = 'amd64' ] || echo 'gcc-x86-64-linux-gnu') \
+		$([ "$dpkgArch" = 'arm64' ] || echo 'gcc-aarch64-linux-gnu') \
 		gcc-arm-linux-gnueabi \
 		gcc-arm-linux-gnueabihf \
 		gcc-i686-linux-gnu \
@@ -54,44 +59,43 @@ RUN set -eux; \
 WORKDIR /usr/src/hello
 COPY . .
 
+# the following steps are grouped into "architecture families" and roughly ordered in a descending compatibility way such that we end up with the most accurate ".host-arch" symlink we can reasonably get
+
 RUN set -ex; \
 	make clean all test \
 		TARGET_ARCH='amd64' \
 		CROSS_COMPILE='x86_64-linux-gnu-' \
 		ARCH_TEST='amd64'
-
 RUN set -ex; \
 	make clean all test \
-		TARGET_ARCH='arm32v5' \
-		CROSS_COMPILE='arm-linux-gnueabi-' \
-#		EXTRA_CFLAGS='-march=armv5te' \
-		ARCH_TEST='armel'
+		TARGET_ARCH='i386' \
+		CROSS_COMPILE='i686-linux-gnu-' \
+		ARCH_TEST='i386'
 
 RUN set -ex; \
 	make clean all test \
-		TARGET_ARCH='arm32v6' \
-		CROSS_COMPILE='arm-linux-gnueabi-' \
-		EXTRA_CFLAGS='-march=armv6+fp' \
-		ARCH_TEST='armhf'
+		TARGET_ARCH='arm64v8' \
+		CROSS_COMPILE='aarch64-linux-gnu-' \
+		ARCH_TEST='arm64'
 
 RUN set -ex; \
 	make clean all test \
 		TARGET_ARCH='arm32v7' \
 		CROSS_COMPILE='arm-linux-gnueabihf-' \
 #		EXTRA_CFLAGS='-march=armv7-a+fp' \
 		ARCH_TEST='armhf'
-
 RUN set -ex; \
 	make clean all test \
-		TARGET_ARCH='arm64v8' \
-		CROSS_COMPILE='aarch64-linux-gnu-' \
-		ARCH_TEST='arm64'
-
+		TARGET_ARCH='arm32v6' \
+		CROSS_COMPILE='arm-linux-gnueabi-' \
+		EXTRA_CFLAGS='-march=armv6+fp' \
+		ARCH_TEST='armhf'
 RUN set -ex; \
 	make clean all test \
-		TARGET_ARCH='i386' \
-		CROSS_COMPILE='i686-linux-gnu-' \
-		ARCH_TEST='i386'
+		TARGET_ARCH='arm32v5' \
+		CROSS_COMPILE='arm-linux-gnueabi-' \
+#		EXTRA_CFLAGS='-march=armv5te' \
+		ARCH_TEST='armel'
 
 RUN set -ex; \
 	make clean all test \
@@ -118,6 +122,6 @@ RUN set -ex; \
 		CROSS_COMPILE='s390x-linux-gnu-' \
 		ARCH_TEST='s390x'
 
-RUN find \( -name 'hello' -or -name 'hello.txt' \) -exec file '{}' + -exec ls -lh '{}' +
+RUN find \( -name 'hello' -or -name 'hello.txt' -or -name '.host-arch' \) -exec file '{}' + -exec ls -lh '{}' +
 
-CMD ["./amd64/hello-world/hello"]
+CMD [".host-arch/hello-world/hello"]

Makefile

@@ -55,6 +55,9 @@ test: $(C_TARGETS)
 		if [ -n "$$ARCH_TEST" ] && command -v arch-test > /dev/null && arch-test "$$ARCH_TEST" > /dev/null; then \
 			( set -x && "./$$b" ); \
 			( set -x && "./$$b" | grep -q '"'"$$(basename "$$(dirname "$$b")")"'"' ); \
+			if [ ! -e .host-arch ] && arch-test -n "$$ARCH_TEST" > /dev/null; then \
+				ln -svfT "$${b%%/*}" .host-arch; \
+			fi; \
 		else \
 			echo >&2 "warning: $$TARGET_ARCH ($$ARCH_TEST) not supported; skipping test"; \
 		fi; \

update.sh

@@ -8,7 +8,7 @@ set -x
 docker build -f Dockerfile.build -t hello-world:build .
 
 find */ \( -name hello -or -name hello.txt \) -delete
-docker run --rm hello-world:build sh -c 'find \( -name hello -or -name hello.txt \) -print0 | xargs -0 tar --create' | tar --extract --verbose
+docker run --rm hello-world:build sh -c 'find \( -name hello -or -name hello.txt -or -name .host-arch \) -print0 | xargs -0 tar --create' | tar --extract --verbose
 
 find -name hello -type f -exec dirname '{}' ';' | xargs -n1 -i'{}' cp Dockerfile-linux.template '{}/Dockerfile'
 find -name hello.txt -type f -exec dirname '{}' ';' | xargs -n1 -i'{}' cp Dockerfile-windows.template '{}/Dockerfile'
@@ -20,7 +20,7 @@ for h in */*/nanoserver-*/Dockerfile; do
 	sed -i 's!FROM .*!FROM mcr.microsoft.com/windows/nanoserver:'"$nano"'!' "$h"
 done
 
-for h in amd64/*/hello; do
+for h in .host-arch/*/hello; do
 	d="$(dirname "$h")"
 	b="$(basename "$d")"
 	"$h" > /dev/null