FindCUDAToolkit: Robust version checks when CUDA lang is not enabled

Previously if you set `CMAKE_CUDA_COMPILER` but hadn't enabled
the CUDA language, FindCUDAToolkit would not correctly compute
the version information.

2 files changed, 34 insertions, 0 deletions

diff --git a/Tests/CudaOnly/ToolkitBeforeLang/CMakeLists.txt b/Tests/CudaOnly/ToolkitBeforeLang/CMakeLists.txt
new file mode 100644
index 0000000..8dff6cc
--- /dev/null
+++ b/Tests/CudaOnly/ToolkitBeforeLang/CMakeLists.txt
@@ -0,0 +1,26 @@
+cmake_minimum_required(VERSION 3.15)
+project(CudaOnlyToolkitBeforeLang CXX)
+
+# Validate that CUDAToolkit gets the correct version
+# when called before CUDA the language is enabled
+find_package(CUDAToolkit REQUIRED)
+enable_language(CUDA)
+
+if(NOT DEFINED CUDAToolkit_VERSION)
+  message(FATAL_ERROR "expected CUDAToolkit variable CUDAToolkit_VERSION not found")
+endif()
+
+set(cuda_libs cudart cuda_driver)
+
+# Verify that all the CUDA:: targets and variables exist
+foreach (cuda_lib IN LISTS cuda_libs)
+  if(NOT CUDA_${cuda_lib}_LIBRARY)
+    message(FATAL_ERROR "expected CUDAToolkit variable CUDA_${cuda_lib}_LIBRARY not found")
+  endif()
+  if(NOT TARGET CUDA::${cuda_lib})
+    message(FATAL_ERROR "expected CUDAToolkit target CUDA::${cuda_lib} not found")
+  endif()
+endforeach()
+
+add_executable(CudaOnlyToolkitBeforeLang main.cu)
+target_link_libraries(CudaOnlyToolkitBeforeLang PRIVATE CUDA::toolkit)
diff --git a/Tests/CudaOnly/ToolkitBeforeLang/main.cu b/Tests/CudaOnly/ToolkitBeforeLang/main.cu
new file mode 100644
index 0000000..0f3ccdc
--- /dev/null
+++ b/Tests/CudaOnly/ToolkitBeforeLang/main.cu
@@ -0,0 +1,8 @@
+// Only thing we care about is that these headers are found
+#include <cuda.h>
+#include <cuda_runtime_api.h>
+
+int main(int argc, char** argv)
+{
+  return 0;
+}