Switch to C officially, especially for multi-architecture compatibility

Dockerfile.build

@@ -1,10 +1,17 @@
+# explicitly use Debian for maximum cross-architecture compatibility
 FROM debian:jessie
 
-RUN apt-get update && apt-get install -y make nasm && rm -rf /var/lib/apt/lists/*
+RUN apt-get update && apt-get install -y --no-install-recommends \
+		gcc \
+		libc6-dev \
+		make \
+	&& rm -rf /var/lib/apt/lists/*
 
 WORKDIR /usr/src/hello
 COPY . .
 
-RUN make clean all test
+RUN set -x \
+	&& make clean all test \
+	&& ls -l */hello
 
 CMD ["./hello-world/hello"]

Makefile

@@ -1,24 +1,21 @@
-IMAGES := \
-	hello-world \
-	hola-mundo \
-	hello-seattle
+C_TARGETS := $(addsuffix hello, $(wildcard */))
 
-ASM_TARGETS := $(addsuffix /hello, $(IMAGES))
+CC := gcc
+CFLAGS := -static -Os -nostartfiles -fno-asynchronous-unwind-tables
 
 .PHONY: all
-all: $(ASM_TARGETS)
+all: $(C_TARGETS)
 
-$(ASM_TARGETS): hello.asm
-	mkdir -p '$(dir $@)'
-	nasm -o '$@' -DDOCKER_IMAGE="'$$(dirname '$@')'" '$<'
-	chmod +x '$@'
+$(C_TARGETS): hello.c
+	$(CC) $(CFLAGS) -o '$@' -D DOCKER_IMAGE='"$(@D)"' -D DOCKER_GREETING="\"$$(cat '$(@D)/greeting.txt')\"" '$<'
+	strip -R .comment -s '$@'
 
 .PHONY: clean
 clean:
-	-rm -vrf $(addsuffix /, $(IMAGES))
+	-rm -vrf $(C_TARGETS)
 
 .PHONY: test
-test: $(ASM_TARGETS)
+test: $(C_TARGETS)
 	@for b in $^; do \
 		( set -x && "./$$b" ); \
 		( set -x && "./$$b" | grep -q '"'"$$(dirname "$$b")"'"' ); \

hello-seattle/greeting.txt

@@ -0,0 +1 @@
+Hello from DockerCon 2016 (Seattle)!

hello-world/greeting.txt

@@ -0,0 +1 @@
+Hello from Docker!

hello.c

@@ -0,0 +1,41 @@
+//#include <unistd.h>
+#include <sys/syscall.h>
+
+#ifndef DOCKER_IMAGE
+	#define DOCKER_IMAGE "hello-world"
+#endif
+
+#ifndef DOCKER_GREETING
+	#define DOCKER_GREETING "Hello from Docker!"
+#endif
+
+const char message[] =
+	"\n"
+	DOCKER_GREETING "\n"
+	"This message shows that your installation appears to be working correctly.\n"
+	"\n"
+	"To generate this message, Docker took the following steps:\n"
+	" 1. The Docker client contacted the Docker daemon.\n"
+	" 2. The Docker daemon pulled the \"" DOCKER_IMAGE "\" image from the Docker Hub.\n"
+	" 3. The Docker daemon created a new container from that image which runs the\n"
+	"    executable that produces the output you are currently reading.\n"
+	" 4. The Docker daemon streamed that output to the Docker client, which sent it\n"
+	"    to your terminal.\n"
+	"\n"
+	"To try something more ambitious, you can run an Ubuntu container with:\n"
+	" $ docker run -it ubuntu bash\n"
+	"\n"
+	"Share images, automate workflows, and more with a free Docker Hub account:\n"
+	" https://hub.docker.com\n"
+	"\n"
+	"For more examples and ideas, visit:\n"
+	" https://docs.docker.com/engine/userguide/\n"
+	"\n";
+
+void _start() {
+	//write(1, message, sizeof(message) - 1);
+	syscall(SYS_write, 1, message, sizeof(message) - 1);
+
+	//_exit(0);
+	syscall(SYS_exit, 0);
+}

hola-mundo/greeting.txt

@@ -0,0 +1 @@
+¡Hola de DockerCon EU 2015 (Barcelona)!

update.sh

@@ -4,13 +4,15 @@ set -e
 cd "$(dirname "$(readlink -f "$BASH_SOURCE")")"
 
 set -x
+
 docker build -f Dockerfile.build -t hello-world:build .
-rm -rf */
-docker run --rm hello-world:build sh -c 'tar -c */' | tar -x
-for d in */; do
-	d="${d%/}"
-	cp -v Dockerfile.template "$d/Dockerfile"
-	"./$d/hello" > /dev/null
+
+rm -rf */hello
+docker run --rm hello-world:build sh -c 'tar --create */hello' | tar --extract --wildcards '*/hello'
+
+for h in */hello; do
+	d="$(dirname "$h")"
+	"$h" > /dev/null
 	docker build -t hello-world:"test-$d" "$d"
 	docker run --rm hello-world:"test-$d"
 done