set C++ version where necessary, remove checks where unnecessary

ginkgo has the PUBLIC property cxx_std_17,
so we don't need to set it in tests.
pkg-config doesn't propagate C++ standards

benchmark/CMakeLists.txt

@@ -35,7 +35,6 @@ function(ginkgo_benchmark_onemkl_linops type def)
     add_library(onemkl_linops_${type} utils/dpcpp_linops.dp.cpp)
     # make the dependency public to catch issues
     target_compile_definitions(onemkl_linops_${type} PUBLIC ${def})
-    target_compile_features(onemkl_linops_${type} PRIVATE cxx_std_17)
     target_link_libraries(onemkl_linops_${type} PRIVATE Ginkgo::ginkgo MKL::MKL_DPCPP)
 endfunction()
 

cmake/create_test.cmake

@@ -32,7 +32,6 @@ function(ginkgo_set_test_target_properties test_target_name test_library_suffix)
     else()
         target_link_libraries(${test_target_name} PRIVATE ginkgo_gtest_main${test_library_suffix})
     endif()
-    target_compile_features(${test_target_name} PUBLIC cxx_std_14)
     # we set these properties regardless of the enabled backends,
     # because unknown properties are ignored
     set_target_properties(${test_target_name} PROPERTIES HIP_STANDARD 17)
@@ -129,7 +128,6 @@ endfunction(ginkgo_create_test)
 function(ginkgo_create_dpcpp_test test_name)
     ginkgo_build_test_name(${test_name} test_target_name)
     add_executable(${test_target_name} ${test_name}.dp.cpp)
-    target_compile_features(${test_target_name} PUBLIC cxx_std_17)
     target_compile_options(${test_target_name} PRIVATE ${GINKGO_DPCPP_FLAGS})
     gko_add_sycl_to_target(TARGET ${test_target_name} SOURCES ${test_name}.dp.cpp)
     target_link_options(${test_target_name} PRIVATE -fsycl-device-code-split=per_kernel)
@@ -260,7 +258,6 @@ function(ginkgo_create_common_device_test test_name)
     ginkgo_build_test_name(${test_name} test_target_name)
     if(GINKGO_BUILD_SYCL)
         ginkgo_create_common_test_internal(${test_name} DpcppExecutor dpcpp ${ARGN})
-        target_compile_features(${test_target_name}_dpcpp PRIVATE cxx_std_17)
         target_compile_options(${test_target_name}_dpcpp PRIVATE ${GINKGO_DPCPP_FLAGS})
         # We need to use a new file to avoid sycl setting in other backends because add_sycl_to_target will change the source property.
         configure_file(${test_name}.cpp ${test_name}.dp.cpp COPYONLY)

dpcpp/CMakeLists.txt

@@ -101,7 +101,6 @@ gko_add_sycl_to_target(TARGET ginkgo_dpcpp)
 # Note: add MKL as PRIVATE not PUBLIC (MKL example shows) to avoid propagating
 # find_package(MKL) everywhere when linking ginkgo (see the MKL example
 # https://software.intel.com/content/www/us/en/develop/documentation/onemkl-windows-developer-guide/top/getting-started/cmake-config-for-onemkl.html)
-target_compile_features(ginkgo_dpcpp PUBLIC cxx_std_17)
 target_link_options(ginkgo_dpcpp PRIVATE -fsycl-device-lib=all)
 # When building ginkgo as a static library, we need to use dpcpp and per_kernel
 # link option when the program uses a dpcpp related function.

test/test_exportbuild/CMakeLists.txt

@@ -7,5 +7,4 @@ find_package(Ginkgo REQUIRED
 # Here, we use test install without any data. We instantiate the
 # interface only.
 add_executable(test_exportbuild ../test_install/test_install.cpp)
-target_compile_features(test_exportbuild PUBLIC cxx_std_14)
 target_link_libraries(test_exportbuild PRIVATE Ginkgo::ginkgo)

test/test_install/CMakeLists.txt

@@ -26,7 +26,6 @@ if (GINKGO_BUILD_REFERENCE)
     set(HAS_REFERENCE 1)
 endif()
 add_executable(test_install test_install.cpp)
-target_compile_features(test_install PUBLIC cxx_std_14)
 target_compile_definitions(test_install PRIVATE HAS_REFERENCE=${HAS_REFERENCE})
 target_link_libraries(test_install PRIVATE Ginkgo::ginkgo)
 if(GINKGO_BUILD_MPI)

test/test_pkgconfig/CMakeLists.txt

@@ -8,7 +8,7 @@ pkg_check_modules(GINKGO REQUIRED IMPORTED_TARGET ginkgo)
 # Here, we use test install without any data. We instantiate the
 # interface only.
 add_executable(test_pkgconfig ../test_install/test_install.cpp)
-target_compile_features(test_pkgconfig PUBLIC cxx_std_14)
+target_compile_features(test_pkgconfig PUBLIC cxx_std_17)
 # CMake PkgConfig only puts the -l, -L, and -framework into link_libraries and others into link_options
 # When linking the target, the linking option will be before the compiled object to lead the linking error
 set_property(TARGET PkgConfig::GINKGO PROPERTY INTERFACE_LINK_LIBRARIES "${GINKGO_LDFLAGS}")

test/test_subdir/CMakeLists.txt

@@ -5,5 +5,4 @@ file(CREATE_LINK "${CMAKE_CURRENT_SOURCE_DIR}/../.." "${CMAKE_CURRENT_BINARY_DIR
 add_subdirectory("${CMAKE_CURRENT_BINARY_DIR}/ginkgo")
 
 add_executable(test_subdir ../test_install/test_install.cpp)
-target_compile_features(test_subdir PUBLIC cxx_std_14)
 target_link_libraries(test_subdir PRIVATE Ginkgo::ginkgo)