test cuda: add more comment / macro check

* checks both `__NVCC__` and `__CUDACC__`

More comments for CMake and CUDA source file.

test/cuda-test/CMakeLists.txt

@@ -10,20 +10,26 @@
 # And we can't sure most of the CUDA projects are using those latest
 # because the latest C++ standard for NVCC is C++ 14 at this moment.
 #
-# In conclusion, this test will use older version of CMake,
+# In conclusion, 
-# and rely on 'find_package(CUDA)'. For its version, do follow the Root CMakeLists.txt.
+# this test should follow the version of the Root CMakeLists.txt 
+# and rely on 'find_package(CUDA)'. 
 #
 
+#
+# This part is for future update
 #
 # cmake_minimum_required(VERSION 3.10)
 # project(fmt-cuda-test LANGUAGES CXX CUDA) # see 'enable_language(CUDA)'
-cmake_minimum_required(VERSION 3.1) # for C++ 14
+#
+
+# Follow the Root CMakeLists.txt
+cmake_minimum_required(VERSION 3.1) 
 project(fmt-cuda-test LANGUAGES CXX)
 
-# find from ${PROJECT_BINARY_DIR}
+# See 'test/CMakeLists.txt'. It's using ${PROJECT_BINARY_DIR}
 find_package(FMT    REQUIRED) 
 
-# The environment variables(CUDA_BIN_PATH & CUDA_PATH) must be specified at this point
+# The environment variables (CUDA_BIN_PATH & CUDA_PATH) must be specified
 find_package(CUDA   REQUIRED)
 
 #
@@ -44,12 +50,12 @@ endif()
 
 #
 # In this test, we will assume that 
-# the user is going to pre-compile CUDA source codes
+# the user is going to compile CUDA source codes with some libraries.
-# with some libraries (including this 'fmt').
+# Of course, it's 'fmt' in this case.
 #
 # In addition to that, 
-# this test will invoke both C++ Host compiler and NVCC 
+# this test will invoke both C++ Host compiler and NVCC by providing 
-# by providing another (non-CUDA) C++ source code
+# another (non-CUDA) C++ source code
 #
 cuda_add_executable(fmt-in-cuda-test
     cuda-cpp14.cu
@@ -62,12 +68,11 @@ cuda_add_executable(fmt-in-cuda-test
 set_target_properties(fmt-in-cuda-test
 PROPERTIES
     CXX_STANDARD 14 # Notice this is for C++ code
-    POSITION_INDEPENDENT_CODE ON
 )
-# target_compile_features(fmt-in-cuda-test
+target_compile_features(fmt-in-cuda-test
-# PRIVATE
+PRIVATE
-#     cxx_std_14 # just make sure of the property is available
+    cxx_std_14 # just make sure of the property
-# )
+)
 
 get_target_property(cuda_standard 
     fmt-in-cuda-test CUDA_STANDARD
@@ -91,10 +96,13 @@ target_link_libraries(fmt-in-cuda-test
 
 if(MSVC)
     #
-    # MSVC places incorrect '__cplusplus' macro. Follow the guideline.
+    # This part is for (non-CUDA) C++ code.
+    # MSVC can define incorrect '__cplusplus' macro. 
+    # Fix for the issue is to use additional compiler flag. 
     #
-    # https://github.com/Microsoft/vscode-cpptools/issues/2595
+    # See Also:
     # https://devblogs.microsoft.com/cppblog/msvc-now-correctly-reports-__cplusplus/
+    # https://github.com/Microsoft/vscode-cpptools/issues/2595
     #
     target_compile_options(fmt-in-cuda-test
     PRIVATE

test/cuda-test/cpp14.cc

@@ -1,8 +1,14 @@
 
 #include <fmt/core.h>
 
-static_assert(__cplusplus >= 201402L, "expect C++ 2014");
+//
+// The purpose of this part is to ensure NVCC's host compiler also supports
+// the standard version. See 'cuda-cpp14.cu'.
+//
+// https://en.cppreference.com/w/cpp/preprocessor/replace#Predefined_macros
+//
+static_assert(__cplusplus >= 201402L, "expect C++ 2014 for host compiler");
 
-auto make_message_cpp() -> std::string{
+auto make_message_cpp() -> std::string {
-    return fmt::format("host compiler\t: __cplusplus == {}", __cplusplus);
+  return fmt::format("host compiler \t: __cplusplus == {}", __cplusplus);
 }

test/cuda-test/cuda-cpp14.cu

@@ -1,16 +1,31 @@
 
 //
-//  nvcc -x cu -std=c++14 ..\test\cuda-test\include_test.cu -I"../include" -Xcompiler /Zc:__cplusplus  -l"fmtd" -L"../build/Debug"
+//  Direct NVCC command line example:
+//
+//  nvcc.exe ./cuda-cpp14.cu -x cu -I"../include" -l"fmtd" -L"../build/Debug"  \
+//          -std=c++14 -Xcompiler /std:c++14 -Xcompiler /Zc:__cplusplus
 //
 
 //
-// Ensure that we are using the expected standard
+// Ensure that we are using the latest C++ standard for NVCC
+// The version is C++14
+//
+// https://docs.nvidia.com/cuda/cuda-c-programming-guide/index.html#c-cplusplus-language-support
 // https://en.cppreference.com/w/cpp/preprocessor/replace#Predefined_macros
 //
 static_assert(__cplusplus >= 201402L, "expect C++ 2014 for nvcc");
 
-#if defined(__CUDACC__)
+//
-#   define FMT_DEPRECATED
+// https://docs.nvidia.com/cuda/cuda-compiler-driver-nvcc/index.html#nvcc-identification-macro
+//
+// __NVCC__ is for NVCC compiler
+// __CUDACC__ is for CUDA(.cu) source code
+//
+// Since we don't know the actual case in this header, checking both macro
+// will prevent possible pitfalls ...
+//
+#if defined(__NVCC__) || defined(__CUDACC__)
+#  define FMT_DEPRECATED
 #endif
 #include <fmt/core.h>
 
@@ -22,11 +37,11 @@ using namespace std;
 extern auto make_message_cpp() -> std::string;
 extern auto make_message_cuda() -> std::string;
 
-int main(int, char*[]){
+int main(int, char*[]) {
-    cout << make_message_cuda() << endl;
+  cout << make_message_cuda() << endl;
-    cout << make_message_cpp() << endl;
+  cout << make_message_cpp() << endl;
 }
 
-auto make_message_cuda() -> std::string{
+auto make_message_cuda() -> std::string {
-    return fmt::format("nvcc         \t: __cplusplus == {}", __cplusplus);
+  return fmt::format("nvcc compiler \t: __cplusplus == {}", __cplusplus);
 }