Add GCC runtime (libgcc_s.so).

[proger]

Since the scratch image already contains glibc stuff
(because it's impossible to use -optl-static binaries truly
statically linked if GHC runtime uses glibc), it also makes
sense to add the GCC runtime.

It makes the image usable as a base for binaries with dynamically-linked GHC runtimes
at a price of 88 kilobytes.

Also closes #7.

[snoyberg]

See this comment for my reservations about this PR: #7 (comment)

[proger]

It is weird that haskell-scratch is meant to be used for statically binaries — there is an image for that, scratch.

Neither the README, nor the blog post, nor the example Makefile say anything about GHC/Glibc idiosyncrasies wrt static linking (the fact that -optl-static is being used and actually still depends on the use of the dynamic linker and most dynamic libraries, while and libgmp is included for LGPL compliance) — while adding the GCC runtime makes every Haskell dynamically-linked binary without any native dependencies work.

So, given the README says

Base Docker image which includes minimal shared libraries for GHC-compiled executables

I'm merely fixing a bug.

/mnt/haskell-scratch/example# make run
Sending build context to Docker daemon 842.8 kB
Step 0 : FROM fpco/haskell-scratch:integer-gmp
 ---> cc6e8498340d
Step 1 : ADD hello /usr/bin/hello
 ---> Using cache
 ---> 33bcedc11409
Step 2 : CMD hello
 ---> Using cache
 ---> 0c820f48c704
Successfully built 0c820f48c704
hello: error while loading shared libraries: libgcc_s.so.1: cannot open shared object file: No such file or directory
Makefile:11: recipe for target 'run' failed

If you'd like I can squeeze proper README updates in this PR.

[snoyberg]

The assumption that the scratch image is sufficient for GHC-compiled static executables is not true. At the very least, libgmp needs to be present. Other libraries - like iconv and its resources - need to be present as well. That's what this image is designed to solve. I've already updated the README to clarify that this is for statically compiled executables. The reason this was never called out before is because static compilation is the default for GHC.

[proger]

The reason this was never called out before is because static compilation is the default for GHC.

You probably mean static linking of haskell stuff, not "native" stuff.

The problem is still there and the gcc runtime must be present:

root@1b9d2d881d57:/mnt/haskell-scratch/example# make hello SHELL="bash -x"
+ ghc hello.hs
Linking hello ...
+ strip hello
root@1b9d2d881d57:/mnt/haskell-scratch/example# ldd ./hello
    linux-vdso.so.1 =>  (0x00007ffebe7ae000)
    libgmp.so.10 => /usr/lib/x86_64-linux-gnu/libgmp.so.10 (0x00007f874f224000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f874ef1e000)
    librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f874ed16000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f874eb12000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f874e8fc000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f874e537000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f874e319000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f874f498000)
root@1b9d2d881d57:/mnt/haskell-scratch/example# ldd ./hello | grep gcc_s
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f2a63348000)

[snoyberg]

Can you provide the full reproducing case you're using? It's very hard to guess at what's going on here, especially since my tests with the current image have worked for minimalistic examples.

[proger]

I simply try to use the provided example and GHC from fpco/stack-build:lts-3.18 (6eaa0c6bcea6). fpco/haskell-scratch:integer-gmp is cc6e8498340d.

[snoyberg]

I'm not sure what's going on there. Pinging @dysinger who wrote that example to comment. Also pinging @ketzacoatl who may have experimented with it recently.

[proger]

Bumping the thread. I think this matter is still worth pursuing.