Target an even older version of macOS

.github/scripts/install_deps.sh

@@ -30,10 +30,18 @@ case "${OS%%-*}" in
 		sudo apt-get install -yq $pkgs
 		;;
 	macos)
+		pkgs=bison
+		case $TOOLSET in
+			'' | lld)
+				pkgs="$pkgs $TOOLSET"
+				TOOLSET=
+			;;
+		esac
 		# macOS bundles GNU Make 3.81, which doesn't support synced output.
 		# We leave it as the default in `PATH`, to test that our Makefile works with it.
 		# However, CMake automatically uses Homebrew's `gmake`, so our CI has synced output.
-		brew install bison make
+		# shellcheck disable=SC2086 # (This word splitting is intentional.)
+		brew install $pkgs make
 		# Export `bison` to allow using the version we install from Homebrew,
 		# instead of the outdated one preinstalled on macOS (which doesn't even support `-Wall`...).
 		export PATH="$(brew --prefix)/opt/bison/bin:$PATH"

.github/workflows/create-release-artifacts.yml

@@ -57,12 +57,14 @@ jobs:
         uses: actions/checkout@v6
       - name: Install deps
         run: |
-          ./.github/scripts/install_deps.sh macos
+          ./.github/scripts/install_deps.sh macos lld
       - name: Build binaries
         run: |
           cmake -S . -B build --preset macos-static -DFETCHCONTENT_BASE_DIR="${{ env.DEPS_ROOT_DIR }}"
           cmake --build build
           strip rgb{asm,link,fix,gfx}
+        env:
+          LDFLAGS: -fuse-ld=lld # cmake/macos-static.cmake comments explain why we use lld.
       - name: Package binaries
         run: |
           zip --junk-paths rgbds-macos.zip rgb{asm,link,fix,gfx} man/* .github/scripts/install.sh

.github/workflows/testing.yml

@@ -113,7 +113,7 @@ jobs:
         uses: actions/checkout@v6
       - name: Install deps
         run: |
-          .github/scripts/install_deps.sh macos
+          .github/scripts/install_deps.sh macos lld
       - name: Cache library deps
         uses: actions/cache@v5
         with:
@@ -124,6 +124,8 @@ jobs:
         run: |
           cmake -S . -B build --preset macos-static -DFETCHCONTENT_BASE_DIR="${{ env.DEPS_ROOT_DIR }}" -DTESTS_OS_NAME=macos
           cmake --build build
+        env:
+          LDFLAGS: -fuse-ld=lld # cmake/macos-static.cmake comments explain why we use lld.
       - name: Package binaries
         run: |
           mkdir bins

cmake/macos-static.cmake

@@ -2,10 +2,14 @@
 # in order to generate executables compatible with old macOS versions.
 # See our `macos-static` CMake preset for how it's meant to be used.
 
-# The `-mmacosx-version-min=10.9` flag ensures that the binary only uses APIs available on Mac OS X 10.9 Mavericks.
+# Note that targeting old enough versions of Mac OS X on recent enough versions of macOS
+# triggers some poorly-tested code paths within Apple's linker, which then crashes.
+# This can be worked around by using LLVM's LLD linker and passing `-fuse-ld=lld` when linking.
+
+# The `-mmacosx-version-min=10.4` flag ensures that the binary only uses APIs available on Mac OS X 10.4 Tiger.
 # The `-arch` flags build a "fat binary" that works on both Apple architectures:
 # older Intel x64 Macs and newer ARM "Apple Silicon" ones.
-set(secret_sauce -mmacosx-version-min=10.9 "SHELL:-arch x86_64" "SHELL:-arch arm64") # Avoid `-arch` being dedup'd.
+set(secret_sauce -mmacosx-version-min=10.4 "SHELL:-arch x86_64" "SHELL:-arch arm64") # Avoid `-arch` being dedup'd.
 add_compile_options(${secret_sauce})
 add_link_options(${secret_sauce})
 set(PNG_HARDWARE_OPTIMIZATIONS OFF) # These do not play well with a dual-arch build.