Modern CMake: naming convention for CUDA variables

The C++ standard used for CUDA code is set in `CMAKE_CUDA_STANDARD`.
Variable `CMAKE_CUDA_VERSION` was renamed to `MINIMAL_CUDA_VERSION`
for clarity.

CMakeLists.txt

@@ -287,11 +287,12 @@ set(CMAKE_CXX_EXTENSIONS OFF)
 
 # CUDA compiler
 if(WITH_CUDA)
-  set(CMAKE_CUDA_STANDARD 9.0)
+  set(CMAKE_CUDA_STANDARD ${CMAKE_CXX_STANDARD})
+  set(MINIMAL_CUDA_VERSION 9.0)
   set(WITH_CUDA_COMPILER "nvcc" CACHE STRING "Select the CUDA compiler, can be 'nvcc' (default), 'hip', or 'clang'")
   if (WITH_CUDA_COMPILER STREQUAL "nvcc")
-    find_package(CUDA ${CMAKE_CUDA_STANDARD} REQUIRED)
-    find_package(CUDACompilerNVCC ${CMAKE_CUDA_STANDARD} REQUIRED)
+    find_package(CUDA ${MINIMAL_CUDA_VERSION} REQUIRED)
+    find_package(CUDACompilerNVCC ${MINIMAL_CUDA_VERSION} REQUIRED)
   elseif (WITH_CUDA_COMPILER STREQUAL "hip")
     set(ROCM_HOME "/opt/rocm" CACHE FILEPATH "Path to AMD ROCm")
     list(APPEND CMAKE_MODULE_PATH "${ROCM_HOME}/hip/cmake")
@@ -301,7 +302,7 @@ if(WITH_CUDA)
     find_package(HIP 1.5.18494 MODULE REQUIRED)
     find_package(CUDACompilerHIP 6.0 REQUIRED)
   elseif (WITH_CUDA_COMPILER STREQUAL "clang")
-    set(CMAKE_CUDA_STANDARD 8.0)
+    set(MINIMAL_CUDA_VERSION 8.0)
     find_package(CUDACompilerClang 6.0 REQUIRED)
   else()
     message(FATAL_ERROR "Cannot process option -DWITH_CUDA_COMPILER='${WITH_CUDA_COMPILER}'")

cmake/FindCUDACompilerClang.cmake

@@ -28,8 +28,8 @@ message(STATUS "Found CUDA-capable host compiler: ${CMAKE_CUDA_COMPILER}")
 message(STATUS "Found CUDA version: ${CUDA_VERSION}")
 message(STATUS "Found CUDA installation: ${CUDA_DIR}")
 
-if(CUDA_VERSION VERSION_LESS ${CMAKE_CUDA_STANDARD})
-  message(FATAL_ERROR "${CMAKE_CUDA_COMPILER} was built for CUDA ${CUDA_VERSION}: version does not match requirements (CUDA ${CMAKE_CUDA_STANDARD}).")
+if(CUDA_VERSION VERSION_LESS ${MINIMAL_CUDA_VERSION})
+  message(FATAL_ERROR "${CMAKE_CUDA_COMPILER} was built for CUDA ${CUDA_VERSION}: version does not match requirements (CUDA ${MINIMAL_CUDA_VERSION}).")
 endif()
 
 find_library(CUDART_LIBRARY NAMES cudart PATHS ${CUDA_DIR}/lib64 ${CUDA_DIR}/lib /usr/local/nvidia/lib NO_DEFAULT_PATH)

cmake/FindCUDACompilerHIP.cmake

@@ -14,7 +14,7 @@ string(REGEX
                CMAKE_CUDA_COMPILER_VERSION
                "${HIPCC_VERSION_STRING}")
 
-list(APPEND HIP_HCC_FLAGS "-I${HIP_ROOT_DIR}/include -I${ROCM_HOME}/include -Wno-c99-designator -Wno-macro-redefined -Wno-duplicate-decl-specifier -std=c++${CMAKE_CXX_STANDARD}")
+list(APPEND HIP_HCC_FLAGS "-I${HIP_ROOT_DIR}/include -I${ROCM_HOME}/include -Wno-c99-designator -Wno-macro-redefined -Wno-duplicate-decl-specifier -std=c++${CMAKE_CUDA_STANDARD}")
 list(APPEND HIP_HCC_FLAGS "-pedantic -Wall -Wextra -Wno-sign-compare -Wno-unused-function -Wno-unused-variable -Wno-unused-parameter -Wno-missing-braces -Wno-gnu-anonymous-struct -Wno-nested-anon-types -Wno-gnu-zero-variadic-macro-arguments")
 if(WARNINGS_ARE_ERRORS)
   list(APPEND HIP_HCC_FLAGS "-Werror")

cmake/FindCUDACompilerNVCC.cmake

@@ -28,7 +28,7 @@ set(CUDA_NVCC_FLAGS_RELEASE "${CUDA_NVCC_FLAGS_RELEASE} -O3 -DNDEBUG")
 set(CUDA_NVCC_FLAGS_MINSIZEREL "${CUDA_NVCC_FLAGS_MINSIZEREL} -Os -DNDEBUG")
 set(CUDA_NVCC_FLAGS_RELWITHDEBINFO "${CUDA_NVCC_FLAGS_RELWITHDEBINFO} -g -O2")
 
-set(CUDA_NVCC_FLAGS "${CUDA_NVCC_FLAGS} -gencode=arch=compute_30,code=sm_30 -gencode=arch=compute_52,code=sm_52 -gencode=arch=compute_52,code=compute_52 -std=c++${CMAKE_CXX_STANDARD}")
+set(CUDA_NVCC_FLAGS "${CUDA_NVCC_FLAGS} -gencode=arch=compute_30,code=sm_30 -gencode=arch=compute_52,code=sm_52 -gencode=arch=compute_52,code=compute_52 -std=c++${CMAKE_CUDA_STANDARD}")
 if(WARNINGS_ARE_ERRORS)
   set(CUDA_NVCC_FLAGS "${CUDA_NVCC_FLAGS} -Xcompiler -Werror")
 endif()