Switch to C officially, especially for multi-architecture compatibility

[tianon]

Fixes #7
Closes #9 (carried)

[ncopa]

Protip: link static with musl using musl-dev. Will reduce size significantly.

[tianon]

Oh, that is available in Debian! (https://packages.debian.org/sid/musl-dev)

I'll play, thanks! 😄

[tianon]

It appears not to cover s390x, but it does have decent coverage for other arches, so I'll see what I can come up with.

[tianon]

Before: (glibc)

+ ls -l hello-seattle/hello hello-world/hello hola-mundo/hello
-rwxr-xr-x 1 root root 1864 Jun 29 23:37 hello-seattle/hello
-rwxr-xr-x 1 root root 1848 Jun 29 23:37 hello-world/hello
-rwxr-xr-x 1 root root 1864 Jun 29 23:37 hola-mundo/hello

After: (musl)

+ ls -l hello-seattle/hello hello-world/hello hola-mundo/hello
-rwxr-xr-x 1 root root 1760 Jun 30 17:13 hello-seattle/hello
-rwxr-xr-x 1 root root 1736 Jun 30 17:13 hello-world/hello
-rwxr-xr-x 1 root root 1760 Jun 30 17:13 hola-mundo/hello

Changes:

diff --git a/Dockerfile.build b/Dockerfile.build
index ed3de7c..b81d465 100644
--- a/Dockerfile.build
+++ b/Dockerfile.build
@@ -1,10 +1,15 @@
 # explicitly use Debian for maximum cross-architecture compatibility
 FROM debian:jessie

-RUN apt-get update && apt-get install -y --no-install-recommends \
-       gcc \
-       libc6-dev \
-       make \
+RUN set -ex \
+   && apt-get update \
+# s390x does not have "musl-tools" or "musl-dev", so we need a fallback
+   && if apt-cache show musl-tools > /dev/null 2>&1; then \
+       gcc='musl-tools musl-dev'; \
+   else \
+       gcc='gcc libc6-dev'; \
+   fi \
+   && apt-get install -y --no-install-recommends make $gcc \
    && rm -rf /var/lib/apt/lists/*

 WORKDIR /usr/src/hello
diff --git a/Makefile b/Makefile
index d0b0b63..35c0fb4 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,8 @@
+SHELL := /bin/bash
+
 C_TARGETS := $(addsuffix hello, $(wildcard */))

-CC := gcc
+CC := $(shell command -v musl-gcc &> /dev/null && echo musl-gcc || echo gcc)
 CFLAGS := -static -Os -nostartfiles -fno-asynchronous-unwind-tables

 .PHONY: all
diff --git a/hello-seattle/hello b/hello-seattle/hello
index f7ef94c..7e1d530 100755
Binary files a/hello-seattle/hello and b/hello-seattle/hello differ
diff --git a/hello-world/hello b/hello-world/hello
index 7f3f7f8..9f6f7da 100755
Binary files a/hello-world/hello and b/hello-world/hello differ
diff --git a/hola-mundo/hello b/hola-mundo/hello
index 4d6496d..6a8804c 100755
Binary files a/hola-mundo/hello and b/hola-mundo/hello differ

[yosifkit]

LGTM, I don't think ~100 bytes warrants the extra complexity.