Switch to CUDAFLAGS for enable_language(CUDA) support on MSVC, and em…

…it helpful warnings if possible

.github/workflows/Windows.yml

@@ -80,6 +80,7 @@ jobs:
       build_dir: "build"
       config: "Release"
       CMAKE: ${{ matrix.cmake }}
+      CUDAFLAGS: "-allow-unsupported-compiler"
 
     steps:
     - uses: actions/checkout@v3
@@ -115,7 +116,7 @@ jobs:
     - name: Configure CMake
       id: configure
       shell: bash
-      run: cmake . -B ${{ env.build_dir }} -G "${{ matrix.visual_studio }}" -A x64 -DCMAKE_CUDA_FLAGS="--allow-unsupported-compiler"
+      run: cmake . -B ${{ env.build_dir }} -G "${{ matrix.visual_studio }}" -A x64
 
     - name: Configure Error Processing
       if: ${{ (failure() && steps.configure.outcome == 'failure') || success() }}

CMakeLists.txt

@@ -1,12 +1,52 @@
 # Cmake for simple cuda project which uses NVTX markers as an optional thing.
 
-# Set the minimum cmake version to that which supports cuda natively.
-cmake_minimum_required(VERSION VERSION 3.10 FATAL_ERROR)
-
-
-# Name the project and set languages
-project(main CUDA CXX)
-
+# Set the minimum cmake version to that which provides modern CMake CUDA support (CMAKE_CUDA_ARCHITECTURES)
+cmake_minimum_required(VERSION VERSION 3.18 FATAL_ERROR)
+
+# Declare a project without languages, so we can use check_langauge to provide a more helpful error message in some cases
+project(main LANGUAGES NONE)
+# Check for CXX support, which is required
+include(CheckLanguage)
+check_language(CXX)
+if(CMAKE_CXX_COMPILER)
+    enable_language(CXX)
+else()
+    message(FATAL_ERROR "CXX Language support is required but not found")
+endif()
+# Check for CUDA support, once the host compiler has already been found.
+check_language(CUDA)
+if(CMAKE_CUDA_COMPILER)
+    enable_language(CUDA)
+else()
+    # If using MSVC >= 1940 then CUDA <= 12.3 support requires -allow-unsupported-compiler, so warn about this
+    if(MSVC AND MSVC_VERSION VERSION_GREATER_EQUAL "1940")
+        # If this is the case, then CMake >= 3.29.4 is also required, otherwise CMake does not pass -allow-unsupported-compiler along, warn as appropriate
+        if(CMAKE_VERSION VERSION_LESS "3.29.4")
+            message(FATAL_ERROR 
+                " CUDA Language support detection failed with MSVC ${MSVC_VERSION}\n"
+                " \n"
+                " If you have CUDA <= 12.3 installed:\n"
+                "  - You must upgrade CMake to be >= 3.29.4\n"
+                "    The CUDAFLAGS environment variable must include '-allow-unsupported-compiler'\n"
+                "    You must clear the CMake Cache before reconfiguring this project\n"
+                " \n"
+                "  - Alternatively you may upgrade CUDA to >= 12.4 and clear the CMake Cache before reconfiguring"
+            )
+        else()
+            message(FATAL_ERROR 
+                " CUDA Language support detection failed with MSVC ${MSVC_VERSION}\n"
+                " \n"
+                " If you have CUDA <= 12.3 installed:\n"
+                "  - The CUDAFLAGS environment variable must include '-allow-unsupported-compiler'\n"
+                "    You must clear the CMake Cache before reconfiguring this project\n"
+                " \n"
+                "  - Alternatively you may upgrade CUDA to >= 12.4 and clear the CMake Cache before reconfiguring"
+            )
+        endif()
+    endif()
+    # CUDA support is required
+    message(FATAL_ERROR "CUDA Language support is required but not found")
+endif()
 
 # Set a default build type if not passed
 set(default_build_type "Release")