Switch to the C version officially, and make some minor modifications to ensure cross-architecture compatibility is maximized

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"]

Dockerfile.template

@@ -1,3 +0,0 @@
-FROM scratch
-COPY hello /
-CMD ["/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.asm

@@ -1,93 +0,0 @@
-; this is especially thanks to:
-; http://web.archive.org/web/20140528193301/http://blog.markloiseau.com/2012/05/tiny-64-bit-elf-executables
-
-BITS 64
-	org	0x00400000	; Program load offset
-
-; 64-bit ELF header
-ehdr:
-	;  1), 0 (ABI ver.)
-	db 0x7F, "ELF", 2, 1, 1, 0       ; e_ident
-	times 8 db 0                     ; reserved (zeroes)
-
-	dw 2              ; e_type:	Executable file
-	dw 0x3e           ; e_machine:	AMD64
-	dd 1              ; e_version:	current version
-	dq _start         ; e_entry:	program entry address (0x78)
-	dq phdr - $$      ; e_phoff	program header offset (0x40)
-	dq 0              ; e_shoff	no section headers
-	dd 0              ; e_flags	no flags
-	dw ehdrsize       ; e_ehsize:	ELF header size (0x40)
-	dw phdrsize       ; e_phentsize:	program header size (0x38)
-	dw 1              ; e_phnum:	one program header
-	dw 0              ; e_shentsize
-	dw 0              ; e_shnum
-	dw 0              ; e_shstrndx
-
-ehdrsize equ $ - ehdr
-
-; 64-bit ELF program header
-phdr:
-	dd 1              ; p_type:	loadable segment
-	dd 5              ; p_flags	read and execute
-	dq 0              ; p_offset
-	dq $$             ; p_vaddr:	start of the current section
-	dq $$             ; p_paddr:	"		"
-	dq filesize       ; p_filesz
-	dq filesize       ; p_memsz
-	dq 0x200000       ; p_align:	2^11=200000 = section alignment
-
-; program header size
-phdrsize equ $ - phdr
-
-; Hello World!/your program here
-_start:
-
-	; sys_write(stdout, message, length)
-	mov	rax, 1           ; sys_write
-	mov	rdi, 1           ; stdout
-	mov	rsi, message     ; message address
-	mov	rdx, length      ; message string length
-	syscall
-
-	; sys_exit(return_code)
-	mov	rax, 60          ; sys_exit
-	mov	rdi, 0           ; return 0 (success)
-	syscall
-
-%ifndef DOCKER_IMAGE
-	%define DOCKER_IMAGE 'hello-world'
-%endif
-
-	message:
-		db 0x0A
-%ifidn DOCKER_IMAGE, 'hola-mundo'
-		db '¡Hola de DockerCon EU 2015 (Barcelona)!', 0x0A
-%elifidn DOCKER_IMAGE, 'hello-seattle'
-		db 'Hello from DockerCon 2016 (Seattle)!', 0x0A
-%else
-		db 'Hello from Docker!', 0x0A
-%endif
-		db 'This message shows that your installation appears to be working correctly.', 0x0A
-		db 0x0A
-		db 'To generate this message, Docker took the following steps:', 0x0A
-		db ' 1. The Docker client contacted the Docker daemon.', 0x0A
-		db ' 2. The Docker daemon pulled the "', DOCKER_IMAGE, '" image from the Docker Hub.', 0x0A
-		db ' 3. The Docker daemon created a new container from that image which runs the', 0x0A
-		db '    executable that produces the output you are currently reading.', 0x0A
-		db ' 4. The Docker daemon streamed that output to the Docker client, which sent it', 0x0A
-		db '    to your terminal.', 0x0A
-		db 0x0A
-		db 'To try something more ambitious, you can run an Ubuntu container with:', 0x0A
-		db ' $ docker run -it ubuntu bash', 0x0A
-		db 0x0A
-		db 'Share images, automate workflows, and more with a free Docker Hub account:', 0x0A
-		db ' https://hub.docker.com', 0x0A
-		db 0x0A
-		db 'For more examples and ideas, visit:', 0x0A
-		db ' https://docs.docker.com/engine/userguide/', 0x0A
-		db 0x0A
-	length: equ	$-message            ; message length calculation
-
-; File size calculation
-filesize equ $ - $$

hello.c

@@ -1,21 +1,22 @@
-/* hello.c
+//#include <unistd.h>
+#include <sys/syscall.h>
 
-build with:
+#ifndef DOCKER_IMAGE
+	#define DOCKER_IMAGE "hello-world"
+#endif
 
- gcc -nostartfiles -fno-asynchronous-unwind-tables -Os -static -o hello hello.c
- strip -R .comment -s hello
+#ifndef DOCKER_GREETING
+	#define DOCKER_GREETING "Hello from Docker!"
+#endif
 
-*/
-
-#include <unistd.h>
-
-const char message[] = "\n"
-"Hello from Docker.\n"
+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 \"hello-world\" image from the Docker Hub.\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"
@@ -28,12 +29,13 @@ const char message[] = "\n"
 	" https://hub.docker.com\n"
 	"\n"
 	"For more examples and ideas, visit:\n"
-" https://docs.docker.com/userguide/\n"
+	" https://docs.docker.com/engine/userguide/\n"
 	"\n";
 
-void _start()
-{
-	write(1, message, sizeof(message)-1);
-	_exit(0);
-}
+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