Run CI on a big-endian system

.github/workflows/i386.yml

@@ -13,6 +13,7 @@ defaults:
     shell: bash
 
 jobs:
+  # i386 is 32-bit
   i386:
     runs-on: ubuntu-latest
     container:
@@ -27,5 +28,7 @@ jobs:
     - name: Test
       run: |
         source ~/.ghcup/env
+        ghc --version
+        cabal --version
         cabal update
         cabal test all

.github/workflows/s390x.yml

@@ -0,0 +1,56 @@
+name: s390x CI
+
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
+
+jobs:
+  # s390x is 31-bit-address/32-bit-data and big-endian
+  s390x:
+    runs-on: ubuntu-latest
+
+    # Not required, but speeds up builds by storing container images in a
+    # GitHub package registry.
+    permissions:
+      packages: write
+
+    steps:
+    - uses: actions/checkout@v6
+    - uses: uraimo/run-on-arch-action@v3
+      with:
+        arch: s390x
+
+        # ubuntu_rolling is currently Ubuntu 25. Consider switching this to an
+        # LTS.
+        # Do not use ubuntu24.04 since it comes with ghc and cabal versions that
+        # segfault (possibly https://gitlab.haskell.org/ghc/ghc/-/issues/24163).
+        distro: ubuntu_rolling
+
+        # Not required, but speeds up builds by storing container images in a
+        # GitHub package registry.
+        githubToken: ${{ github.token }}
+
+        # Install GHC via apt because GHCup doesn't support s390x
+        install: |
+          apt-get update -y
+          apt-get install -y ghc cabal-install
+
+        # Test without optimizations because it is much slower otherwise
+        run: |
+          ghc --version
+          cabal --version
+          sed -i 's/containers\//-- &/' cabal.project
+          cat cabal.project
+          cat >> cabal.project.local <<EOF
+          package *
+            optimization: 0
+          package containers-tests
+            -- This overrides the -O2 in containers-tests's ghc-options
+            ghc-options: -O0
+          EOF
+          cabal update
+          cabal test all

containers-tests/containers-tests.cabal

@@ -332,7 +332,6 @@ test-suite map-lazy-properties
   build-depends:
       test-utils
 
-  ghc-options:      -O2
   other-extensions:
     BangPatterns
     CPP
@@ -348,7 +347,6 @@ test-suite map-strict-properties
   build-depends:
       test-utils
 
-  ghc-options:      -O2
   other-extensions:
     BangPatterns
     CPP
@@ -359,7 +357,7 @@ test-suite bitqueue-properties
   hs-source-dirs:   tests
   main-is:          bitqueue-properties.hs
   type:             exitcode-stdio-1.0
-  ghc-options:      -O2
+
   other-extensions:
     BangPatterns
     CPP
@@ -374,7 +372,6 @@ test-suite set-properties
   build-depends:
       test-utils
 
-  ghc-options:      -O2
   other-extensions:
     BangPatterns
     CPP
@@ -389,7 +386,6 @@ test-suite intmap-lazy-properties
   build-depends:
       test-utils
 
-  ghc-options:      -O2
   other-extensions:
     BangPatterns
     CPP
@@ -405,7 +401,6 @@ test-suite intmap-strict-properties
   build-depends:
       test-utils
 
-  ghc-options:      -O2
   other-extensions:
     BangPatterns
     CPP
@@ -420,7 +415,6 @@ test-suite intset-properties
   build-depends:
       test-utils
 
-  ghc-options:      -O2
   other-extensions:
     BangPatterns
     CPP
@@ -436,7 +430,6 @@ test-suite seq-properties
       test-utils
     , ChasingBottoms
 
-  ghc-options:      -O2
   other-extensions:
     BangPatterns
     CPP
@@ -448,7 +441,6 @@ test-suite tree-properties
   main-is:          tree-properties.hs
   type:             exitcode-stdio-1.0
 
-  ghc-options:      -O2
   other-extensions:
     BangPatterns
     CPP
@@ -459,7 +451,6 @@ test-suite graph-properties
   hs-source-dirs:   tests
   main-is:          graph-properties.hs
   type:             exitcode-stdio-1.0
-  ghc-options:      -O2
 
 test-suite map-strictness-properties
   import: test-deps, warnings