remove MDSPAN_CXX_STANDARD

CMakeLists.txt

@@ -25,63 +25,6 @@ option(MDSPAN_USE_SYSTEM_GTEST "Use system-installed GoogleTest library for test
 option(MDSPAN_USE_SYSTEM_BENCHMARK "Use system-installed Google Benchmark library for benchmarks." On)
 option(MDSPAN_INSTALL_STDMODE_HEADERS "Whether to install headers to emulate standard library headers and namespaces" Off)
 
-# Option to override which C++ standard to use
-set(MDSPAN_CXX_STANDARD DETECT CACHE STRING "Override the default CXX_STANDARD to compile with.")
-set_property(CACHE MDSPAN_CXX_STANDARD PROPERTY STRINGS DETECT 14 17 20 23)
-
-option(MDSPAN_ENABLE_CONCEPTS "Try to enable concepts support by giving extra flags." On)
-
-################################################################################
-
-# Decide on the standard to use
-if(MDSPAN_CXX_STANDARD STREQUAL "17")
-  if("cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
-    message(STATUS "Using C++17 standard")
-    set(CMAKE_CXX_STANDARD 17)
-  else()
-    message(FATAL_ERROR "Requested MDSPAN_CXX_STANDARD \"17\" not supported by provided C++ compiler")
-  endif()
-elseif(MDSPAN_CXX_STANDARD STREQUAL "14")
-  if("cxx_std_14" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
-    message(STATUS "Using C++14 standard")
-    set(CMAKE_CXX_STANDARD 14)
-  else()
-    message(FATAL_ERROR "Requested MDSPAN_CXX_STANDARD \"14\" not supported by provided C++ compiler")
-  endif()
-elseif(MDSPAN_CXX_STANDARD STREQUAL "20")
-  if("cxx_std_20" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
-    message(STATUS "Using C++20 standard")
-    set(CMAKE_CXX_STANDARD 20)
-  else()
-    message(FATAL_ERROR "Requested MDSPAN_CXX_STANDARD \"20\" not supported by provided C++ compiler")
-  endif()
-elseif(MDSPAN_CXX_STANDARD STREQUAL "23")
-  if("cxx_std_23" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
-    message(STATUS "Using C++23 standard")
-    set(CMAKE_CXX_STANDARD 23)
-  else()
-    message(FATAL_ERROR "Requested MDSPAN_CXX_STANDARD \"23\" not supported by provided C++ compiler")
-  endif()
-else()
-  if("cxx_std_23" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
-    set(CMAKE_CXX_STANDARD 23)
-    message(STATUS "Detected support for C++23 standard")
-  elseif("cxx_std_20" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
-    set(CMAKE_CXX_STANDARD 20)
-    message(STATUS "Detected support for C++20 standard")
-  elseif("cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
-    set(CMAKE_CXX_STANDARD 17)
-    message(STATUS "Detected support for C++17 standard")
-  elseif("cxx_std_14" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
-    set(CMAKE_CXX_STANDARD 14)
-    message(STATUS "Detected support for C++14 standard")
-  else()
-    message(FATAL_ERROR "Cannot detect CXX_STANDARD of C++14 or newer.")
-  endif()
-endif()
-
-################################################################################
-
 if(MDSPAN_ENABLE_CUDA)
   include(CheckLanguage)
   check_language(CUDA)
@@ -119,6 +62,9 @@ endif()
 add_library(mdspan INTERFACE)
 add_library(std::mdspan ALIAS mdspan)
 
+# Require a minimum of C++14
+target_compile_features(mdspan INTERFACE cxx_std_14)
+
 if(MDSPAN_ENABLE_SYCL)
   target_compile_options(mdspan INTERFACE "-fsycl")
   target_link_options(mdspan INTERFACE "-fsycl")
@@ -181,7 +127,7 @@ if(MDSPAN_ENABLE_EXAMPLES)
 endif()
 
 if(MDSPAN_ENABLE_BENCHMARKS)
-  if(NOT MDSPAN_CXX_STANDARD STREQUAL "14" AND NOT MDSPAN_CXX_STANDARD STREQUAL "23")
+  if("cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
     add_subdirectory(benchmarks)
   else()
     MESSAGE(FATAL_ERROR "Benchmarks are not available in C++14 or C++23 mode. Turn MDSPAN_ENABLE_BENCHMARKS OFF or use C++17 or C++20.")

benchmarks/CMakeLists.txt

@@ -7,6 +7,7 @@ function(mdspan_add_benchmark EXENAME)
   )
   # Set flag to build with parenthesis enabled
   target_compile_definitions(${EXENAME} PRIVATE MDSPAN_USE_PAREN_OPERATOR=1)
+  target_compile_features(${EXENAME} PRIVATE cxx_std_17)
 endfunction()
 
 if(MDSPAN_USE_SYSTEM_BENCHMARK)
@@ -81,6 +82,7 @@ function(mdspan_add_openmp_benchmark EXENAME)
         $<BUILD_INTERFACE:${CMAKE_SOURCE_DIR}/benchmarks>
       )
       target_compile_definitions(${EXENAME} PRIVATE MDSPAN_USE_PAREN_OPERATOR=1)
+      target_compile_features(${EXENAME} PRIVATE cxx_std_17)
     else()
       message(WARNING "Not adding target ${EXENAME} because OpenMP was not found")
     endif()

compilation_tests/CMakeLists.txt

@@ -21,8 +21,9 @@ if(NOT MDSPAN_ENABLE_CUDA)
   add_compilation_test(ctest_compressed_pair_layout)
 endif()
 add_compilation_test(ctest_constexpr_dereference)
-if(NOT CMAKE_CXX_STANDARD STREQUAL "14")
-add_compilation_test(ctest_constexpr_submdspan)
+if("cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
+  add_compilation_test(ctest_constexpr_submdspan)
+  target_compile_features(ctest_constexpr_submdspan PRIVATE cxx_std_17)
 endif()
 add_compilation_test(ctest_constexpr_layouts)
 add_compilation_test(ctest_namespace_std)

tests/CMakeLists.txt

@@ -8,7 +8,7 @@ endif()
 
 function(mdspan_add_test name)
   set(options ENABLE_PRECONDITIONS)
-  set(one_value SOURCE)
+  set(one_value SOURCE COMPILE_FEATURES)
   set(multi_value)
   cmake_parse_arguments(ARGUMENT "${options}" "${one_value}" "${multi_value}" ${ARGN})
 
@@ -27,6 +27,9 @@ function(mdspan_add_test name)
     PUBLIC
     MDSPAN_IMPL_CHECK_PRECONDITION=$<BOOL:${ARGUMENT_ENABLE_PRECONDITIONS}>
   )
+  if(DEFINED ARGUMENT_COMPILE_FEATURES)
+    target_compile_features(${name} PUBLIC ${ARGUMENT_COMPILE_FEATURES})
+  endif()
 endfunction()
 
 if(MDSPAN_USE_SYSTEM_GTEST)
@@ -88,19 +91,23 @@ mdspan_add_test(test_element_access)
 mdspan_add_test(test_exhaustive_layouts)
 mdspan_add_test(test_layout_ctors)
 mdspan_add_test(test_layout_stride)
-if(NOT CMAKE_CXX_STANDARD STREQUAL "14")
+if("cxx_std_17" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
   mdspan_add_test(test_submdspan)
+  target_compile_features(test_submdspan PRIVATE cxx_std_17)
   mdspan_add_test(test_submdspan_static_slice)
+  target_compile_features(test_submdspan_static_slice PRIVATE cxx_std_17)
   mdspan_add_test(test_layout_padded_left ENABLE_PRECONDITIONS)
+  target_compile_features(test_layout_padded_left PRIVATE cxx_std_17)
   mdspan_add_test(test_layout_padded_right ENABLE_PRECONDITIONS)
+  target_compile_features(test_layout_padded_right PRIVATE cxx_std_17)
 endif()
 # both of those don't work yet since its using vector
 if(NOT MDSPAN_ENABLE_CUDA AND NOT MDSPAN_ENABLE_HIP)
 mdspan_add_test(test_mdarray_ctors)
 mdspan_add_test(test_mdarray_to_mdspan)
 endif()
 
-if(CMAKE_CXX_STANDARD GREATER_EQUAL 20)
+if("cxx_std_20" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
 if((CMAKE_CXX_COMPILER_ID STREQUAL Clang) OR ((CMAKE_CXX_COMPILER_ID STREQUAL GNU) AND (CMAKE_CXX_COMPILER_VERSION GREATER_EQUAL 12.0.0)))
   add_subdirectory(libcxx-backports)
 endif()

tests/libcxx-backports/default_accessor/CMakeLists.txt

@@ -1,6 +1,6 @@
-mdspan_add_test(default_accessor.access.pass)
-mdspan_add_test(default_accessor.ctor.conversion.pass)
-mdspan_add_test(default_accessor.ctor.default.pass)
+mdspan_add_test(default_accessor.access.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(default_accessor.ctor.conversion.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(default_accessor.ctor.default.pass COMPILE_FEATURES cxx_std_20)
 #mdspan_add_test(default_accessor.element_type.verify)
-mdspan_add_test(default_accessor.offset.pass)
-mdspan_add_test(default_accessor.types.pass)
+mdspan_add_test(default_accessor.offset.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(default_accessor.types.pass COMPILE_FEATURES cxx_std_20)

tests/libcxx-backports/extents/CMakeLists.txt

@@ -1,10 +1,10 @@
-mdspan_add_test(comparison.pass)
-mdspan_add_test(conversion.pass)
-mdspan_add_test(ctad.pass)
-mdspan_add_test(ctor_default.pass)
-mdspan_add_test(ctor_from_array.pass)
-mdspan_add_test(ctor_from_integral.pass)
-mdspan_add_test(ctor_from_span.pass)
-mdspan_add_test(dextents.pass)
-mdspan_add_test(obs_static.pass)
-mdspan_add_test(types.pass)
+mdspan_add_test(comparison.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(conversion.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(ctad.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(ctor_default.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(ctor_from_array.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(ctor_from_integral.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(ctor_from_span.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(dextents.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(obs_static.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(types.pass COMPILE_FEATURES cxx_std_20)

tests/libcxx-backports/layout_left/CMakeLists.txt

@@ -1,12 +1,12 @@
-mdspan_add_test(layout_left.comparison.pass)
-mdspan_add_test(layout_left.ctor.default.pass)
-mdspan_add_test(layout_left.ctor.extents.pass)
-mdspan_add_test(layout_left.ctor.layout_right.pass)
-mdspan_add_test(layout_left.ctor.layout_stride.pass)
-mdspan_add_test(layout_left.ctor.mapping.pass)
+mdspan_add_test(layout_left.comparison.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_left.ctor.default.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_left.ctor.extents.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_left.ctor.layout_right.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_left.ctor.layout_stride.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_left.ctor.mapping.pass COMPILE_FEATURES cxx_std_20)
 #mdspan_add_test(layout_left.extents.verify)
-mdspan_add_test(layout_left.index_operator.pass)
-mdspan_add_test(layout_left.properties.pass)
-mdspan_add_test(layout_left.required_span_size.pass)
-mdspan_add_test(layout_left.static_requirements.pass)
-mdspan_add_test(layout_left.stride.pass)
+mdspan_add_test(layout_left.index_operator.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_left.properties.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_left.required_span_size.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_left.static_requirements.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_left.stride.pass COMPILE_FEATURES cxx_std_20)

tests/libcxx-backports/layout_right/CMakeLists.txt

@@ -1,12 +1,12 @@
-mdspan_add_test(layout_right.comparison.pass)
-mdspan_add_test(layout_right.ctor.default.pass)
-mdspan_add_test(layout_right.ctor.extents.pass)
-mdspan_add_test(layout_right.ctor.layout_left.pass)
-mdspan_add_test(layout_right.ctor.layout_stride.pass)
-mdspan_add_test(layout_right.ctor.mapping.pass)
+mdspan_add_test(layout_right.comparison.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_right.ctor.default.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_right.ctor.extents.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_right.ctor.layout_left.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_right.ctor.layout_stride.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_right.ctor.mapping.pass COMPILE_FEATURES cxx_std_20)
 #mdspan_add_test(layout_right.extents.verify)
-mdspan_add_test(layout_right.index_operator.pass)
-mdspan_add_test(layout_right.properties.pass)
-mdspan_add_test(layout_right.required_span_size.pass)
-mdspan_add_test(layout_right.static_requirements.pass)
-mdspan_add_test(layout_right.stride.pass)
+mdspan_add_test(layout_right.index_operator.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_right.properties.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_right.required_span_size.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_right.static_requirements.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_right.stride.pass COMPILE_FEATURES cxx_std_20)

tests/libcxx-backports/layout_stride/CMakeLists.txt

@@ -1,13 +1,13 @@
-mdspan_add_test(layout_stride.comparison.pass)
-mdspan_add_test(layout_stride.ctor.default.pass)
-mdspan_add_test(layout_stride.ctor.extents_array.pass)
-mdspan_add_test(layout_stride.ctor.extents_span.pass)
-mdspan_add_test(layout_stride.ctor.strided_mapping.pass)
-mdspan_add_test(layout_stride.deduction.pass)
+mdspan_add_test(layout_stride.comparison.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_stride.ctor.default.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_stride.ctor.extents_array.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_stride.ctor.extents_span.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_stride.ctor.strided_mapping.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_stride.deduction.pass COMPILE_FEATURES cxx_std_20)
 #mdspan_add_test(layout_stride.extents.verify) //FIXME
-mdspan_add_test(layout_stride.index_operator.pass)
-mdspan_add_test(layout_stride.is_exhaustive_corner_case.pass)
-mdspan_add_test(layout_stride.properties.pass)
-mdspan_add_test(layout_stride.required_span_size.pass)
-mdspan_add_test(layout_stride.static_requirements.pass)
-mdspan_add_test(layout_stride.stride.pass)
+mdspan_add_test(layout_stride.index_operator.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_stride.is_exhaustive_corner_case.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_stride.properties.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_stride.required_span_size.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_stride.static_requirements.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(layout_stride.stride.pass COMPILE_FEATURES cxx_std_20)

tests/libcxx-backports/mdspan/CMakeLists.txt

@@ -1,21 +1,21 @@
-mdspan_add_test(mdspan.assign.pass)
-mdspan_add_test(mdspan.conversion.pass)
+mdspan_add_test(mdspan.assign.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(mdspan.conversion.pass COMPILE_FEATURES cxx_std_20)
 #mdspan_add_test(mdspan.conversion.verify)
-mdspan_add_test(mdspan.ctor.copy.pass)
-mdspan_add_test(mdspan.ctor.default.pass)
-mdspan_add_test(mdspan.ctor.dh_array.pass)
-mdspan_add_test(mdspan.ctor.dh_extents.pass)
-mdspan_add_test(mdspan.ctor.dh_integers.pass)
-mdspan_add_test(mdspan.ctor.dh_map.pass)
-mdspan_add_test(mdspan.ctor.dh_map_acc.pass)
-mdspan_add_test(mdspan.ctor.dh_span.pass)
-mdspan_add_test(mdspan.ctor.move.pass)
-mdspan_add_test(mdspan.deduction.pass)
+mdspan_add_test(mdspan.ctor.copy.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(mdspan.ctor.default.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(mdspan.ctor.dh_array.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(mdspan.ctor.dh_extents.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(mdspan.ctor.dh_integers.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(mdspan.ctor.dh_map.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(mdspan.ctor.dh_map_acc.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(mdspan.ctor.dh_span.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(mdspan.ctor.move.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(mdspan.deduction.pass COMPILE_FEATURES cxx_std_20)
 #mdspan_add_test(mdspan.element_type.verify)
 #mdspan_add_test(mdspan.extents.verify)
-mdspan_add_test(mdspan.index_operator.pass)
+mdspan_add_test(mdspan.index_operator.pass COMPILE_FEATURES cxx_std_20)
 #mdspan_add_test(mdspan.mapping.verify)
-mdspan_add_test(mdspan.move.pass)
-mdspan_add_test(mdspan.properties.pass)
-mdspan_add_test(mdspan.swap.pass)
-mdspan_add_test(mdspan.types.pass)
+mdspan_add_test(mdspan.move.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(mdspan.properties.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(mdspan.swap.pass COMPILE_FEATURES cxx_std_20)
+mdspan_add_test(mdspan.types.pass COMPILE_FEATURES cxx_std_20)