Use LLVM + split-sections

Dockerfile

@@ -1,22 +1,56 @@
 # Build-only image
-FROM ubuntu:17.10 AS build
+FROM ubuntu:18.04 AS build
 USER root
 WORKDIR /opt/shellCheck
 
-# Install OS deps
+# Install OS deps, including GHC from HVR-PPA
-RUN apt-get update && apt-get install -y ghc cabal-install
+# https://launchpad.net/~hvr/+archive/ubuntu/ghc
+RUN apt-get -yq update \
+  && apt-get -yq install software-properties-common \
+  && apt-add-repository -y "ppa:hvr/ghc" \
+  && apt-get -yq update \
+  && apt-get -yq install cabal-install-2.4 ghc-8.4.3 llvm-5.0 pandoc \
+  && rm -rf /var/lib/apt/lists/*
+
+ENV PATH="/opt/ghc/bin:/usr/lib/llvm-5.0/bin:${PATH}"
+
+# Use gold linker and check tools versions
+RUN ln -s $(which ld.gold) /usr/local/bin/ld && \
+     cabal --version \
+  && ghc --version \
+  && ld --version
 
 # Install Haskell deps
 # (This is a separate copy/run so that source changes don't require rebuilding)
+#
+# We also patch regex-tdfa and aeson removing hard-coded -O2 flag.
+# This makes compilation faster and binary smaller.
+# Performance loss is unnoticeable for ShellCheck
+#
+# Remember to update versions, once in a while.
 COPY ShellCheck.cabal ./
-RUN cabal update && cabal install --dependencies-only --ghc-options="-optlo-Os -split-sections"
+RUN cabal update && \
+  cabal get regex-tdfa-1.2.3.1 && sed -i 's/-O2//' regex-tdfa-1.2.3.1/regex-tdfa.cabal && \ 
+  cabal get aeson-1.4.0.0 && sed -i 's/-O2//' aeson-1.4.0.0/aeson.cabal && \ 
+  echo 'packages: . regex-tdfa-1.2.3.1 aeson-1.4.0.0 > cabal.project' && \
+  cabal new-build --dependencies-only \
+    --ghc-options='-fllvm -optlo-Os' \
+    --disable-executable-dynamic --enable-split-sections --disable-tests
 
 # Copy source and build it
-COPY LICENSE Setup.hs shellcheck.hs ./
+COPY LICENSE Setup.hs shellcheck.hs shellcheck.1.md ./
 COPY src src
-RUN cabal build Paths_ShellCheck && \
+COPY test test
-  ghc -optl-static -optl-pthread -isrc -idist/build/autogen --make shellcheck -split-sections -optc-Wl,--gc-sections -optlo-Os && \
+# This SED is the only "nastyness" we have to do
+# Hopefully soon we could add per-component ld-options to cabal.project
+RUN sed -i 's/-- STATIC/ld-options: -static -pthread -Wl,--gc-sections/' ShellCheck.cabal && \
+  cat ShellCheck.cabal && \
+  cabal new-build \
+    --ghc-options='-fllvm -optlo-Os' \
+    --disable-executable-dynamic --enable-split-sections --disable-tests && \
+  cp $(find dist-newstyle -type f -name shellcheck) . && \
   strip --strip-all shellcheck && \
+  file shellcheck && \
   ls -l shellcheck
 
 RUN mkdir -p /out/bin && \

ShellCheck.cabal

@@ -28,8 +28,6 @@ Extra-Source-Files:
     shellcheck.1.md
     -- built with a cabal sdist hook
     shellcheck.1
-    -- tests
-    test/shellcheck.hs
 
 custom-setup
   setup-depends:
@@ -94,10 +92,12 @@ executable shellcheck
       directory,
       mtl >= 2.2.1,
       parsec >= 3.0,
-      QuickCheck >= 2.7.4,
       regex-tdfa
     main-is: shellcheck.hs
 
+    -- Marker to add flags for static linking
+    -- STATIC
+
 test-suite doctests
   type:                exitcode-stdio-1.0
   main-is:             doctests.hs