Fix macOS LLVM toolchain setup

Author: DarkaMaul

.github/workflows/build.yml

@@ -148,9 +148,9 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y liblzma-dev
 
-      - name: Install liblzma (macOS)
+      - name: Install macOS dependencies
         if: ${{ runner.os == 'macOS' && steps.ccache-cache.outputs.cache-hit != 'true' }}
-        run: brew install xz
+        run: brew install llvm@18 xz
 
       - name: Install liblzma (Windows)
         if: ${{ matrix.os == 'windows-latest' && steps.ccache-cache.outputs.cache-hit != 'true' }}
@@ -159,7 +159,7 @@ jobs:
       - name: Set LLVM_ROOT (macOS)
         if: ${{ runner.os == 'macOS' && steps.ccache-cache.outputs.cache-hit != 'true' }}
         shell: bash
-        run: echo "LLVM_ROOT_PARAM=-DLLVM_ROOT=$(brew --prefix llvm)" >> "$GITHUB_ENV"
+        run: echo "LLVM_ROOT_PARAM=-DLLVM_ROOT=$(brew --prefix llvm@18)" >> "$GITHUB_ENV"
 
       - name: Configure cmake
         if: steps.ccache-cache.outputs.cache-hit != 'true'
@@ -210,7 +210,7 @@ jobs:
         shell: bash
         run: |
           if [[ "$RUNNER_OS" == "macOS" ]]; then
-            brew install ccache
+            brew install ccache llvm@18
           else
             sudo apt-get update && sudo apt-get install -y ccache
           fi
@@ -503,10 +503,10 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y liblzma-dev
 
-      - name: Install liblzma (MacOS)
+      - name: Install macOS dependencies
         if: ${{ matrix.os == 'macos-latest' }}
         run: |
-          brew install xz
+          brew install llvm@18 xz
 
       - name: Install liblzma (Windows)
         if: ${{ matrix.os == 'windows-latest' }}

CMakeLists.txt

@@ -97,24 +97,27 @@ endif ()
 
 if (UNIX)
     if(APPLE)
+        set(LLVM_HOMEBREW_FORMULA "llvm@18")
         if(DEFINED LLVM_ROOT)
             message(STATUS "Using provided LLVM_ROOT: ${LLVM_ROOT}")
         else()
-            message(WARNING "LLVM_ROOT not provided via -DLLVM_ROOT. Falling back to Homebrew's llvm.")
-            # Fallback to LLVM 15 install path from Homebrew
+            message(WARNING "LLVM_ROOT not provided via -DLLVM_ROOT. Falling back to Homebrew's ${LLVM_HOMEBREW_FORMULA}.")
             execute_process(
-                COMMAND brew --prefix llvm
+                COMMAND brew --prefix ${LLVM_HOMEBREW_FORMULA}
                 OUTPUT_VARIABLE LLVM_ROOT
                 OUTPUT_STRIP_TRAILING_WHITESPACE
             )
 
-            if(NOT EXISTS "${LLVM_ROOT}/bin/clang++")
-                message(FATAL_ERROR "Failed to locate llvm@15 via Homebrew. Please install it or provide LLVM_ROOT manually.")
-            endif()
-
             message(STATUS "Using fallback LLVM_ROOT: ${LLVM_ROOT}")
         endif()
 
+        if(NOT EXISTS "${LLVM_ROOT}/bin/clang" OR NOT EXISTS "${LLVM_ROOT}/bin/clang++")
+            message(FATAL_ERROR
+                "Failed to locate ${LLVM_HOMEBREW_FORMULA} compilers under LLVM_ROOT='${LLVM_ROOT}'. "
+                "Install it with 'brew install ${LLVM_HOMEBREW_FORMULA}' or provide LLVM_ROOT manually."
+            )
+        endif()
+
         add_compile_options(
             "$<$<CONFIG:Debug>:-gfull>"
             -Wno-nullability-completeness