Relink and package mobile libraries from Cabal v2 slices

scripts/nix/README.md

@@ -39,6 +39,16 @@ simulator libraries retain their separate outputs. The existing iOS preparation
 scripts retag ARM64 archives with `mac2ios -s` when an Apple Silicon simulator is
 needed.
 
+The Cabal v2 builder stores ordinary package archives in its staged store.
+`link-mobile-library.sh` relinks the selected package and its dependencies before
+that store is pruned. iOS ZIPs contain both the plain `libHSsimplex-chat-*.a` and
+the rolled `libHSsimplex-chat-*-ghc*.a` used by `update-pbxproj.sh`. Android and
+Windows clients link the threaded RTS into `libsimplex.so` or `libsimplex.dll`;
+Android's separate `libsupport.so` resolves RTS symbols from the client library.
+ARM64 Android libraries retain the 16 KiB linker alignment. These steps run in
+the derivation's build/install phases because v2 component overrides do not run
+the older `postBuild` and `postInstall` hooks.
+
 `NIX_ARGS` passes additional options to `nix build`, and `NIX_OUT_DIR` changes the
 output-link directory. Each derivation has a two-hour timeout by default; set
 `NIX_BUILD_TIMEOUT` in seconds to change it. For a wall-clock limit on a local

scripts/nix/link-mobile-library.sh

@@ -0,0 +1,78 @@
+#!/usr/bin/env bash
+# Relink a Cabal v2 store unit before haskell.nix prunes its composed store.
+set -euo pipefail
+
+if (( $# < 6 )); then
+  echo "usage: $0 GHC GHC_PKG PACKAGE_DB PACKAGE KIND OUTPUT_DIR [LINK_OPTION ...]" >&2
+  exit 2
+fi
+ghc=$1
+ghc_pkg=$2
+package_db=$3
+package=$4
+kind=$5
+output_dir=$6
+shift 6
+mkdir -p "$output_dir/dist"
+output_dir=$(cd "$output_dir" && pwd)
+
+read -r -a units <<< "$("$ghc_pkg" --package-db="$package_db" field "$package" id --simple-output)"
+if (( ${#units[@]} != 1 )); then
+  echo "expected one $package unit in $package_db, got: ${units[*]}" >&2
+  exit 1
+fi
+unit=${units[0]}
+read -r -a libraries <<< "$("$ghc_pkg" --package-db="$package_db" field --ipid "$unit" hs-libraries --simple-output)"
+read -r -a library_dirs <<< "$("$ghc_pkg" --package-db="$package_db" field --ipid "$unit" library-dirs --simple-output)"
+if (( ${#libraries[@]} != 1 )); then
+  echo "expected one Haskell archive for $unit, got: ${libraries[*]}" >&2
+  exit 1
+fi
+archive=""
+for directory in "${library_dirs[@]}"; do
+  if [[ -f "$directory/lib${libraries[0]}.a" ]]; then
+    archive="$directory/lib${libraries[0]}.a"
+    break
+  fi
+done
+if [[ -z "$archive" ]]; then
+  echo "cannot find the vanilla Haskell archive for $unit" >&2
+  exit 1
+fi
+
+# A source input makes GHC perform the final link even with only -package-id.
+# It must not implicitly import the build machine's Prelude on cross targets.
+cat > "$output_dir/MobileBundle.hs" <<'EOF'
+{-# LANGUAGE NoImplicitPrelude #-}
+module MobileBundle () where
+EOF
+cd "$output_dir"
+common=(-v0 -no-hs-main -hide-all-packages -package-db "$package_db")
+case "$kind" in
+  ios)
+    # Xcode's update-pbxproj.sh consumes both the plain and rolled archives.
+    plain=$(basename "$archive")
+    cp "$archive" "dist/$plain"
+    version=$("$ghc" --numeric-version)
+    "$ghc" "${common[@]}" -staticlib -threaded -package-id "$unit" \
+      "$@" MobileBundle.hs -o "dist/${plain%.a}-ghc$version.a"
+    ;;
+  android | windows)
+    if [[ "$kind" == android ]]; then
+      output=libsimplex.so
+    else
+      output=libsimplex.dll
+    fi
+    "$ghc" "${common[@]}" -shared -threaded -flink-rts -package-id "$unit" \
+      "$@" MobileBundle.hs -o "$output"
+    ;;
+  android-support)
+    # libsimplex supplies the RTS/base symbols; do not bundle a second RTS.
+    "$ghc" "${common[@]}" -shared -fno-link-rts -no-auto-link-packages \
+      "$@" "$archive" MobileBundle.hs -o libsupport.so
+    ;;
+  *)
+    echo "unknown mobile library kind: $kind" >&2
+    exit 2
+    ;;
+esac