Enabled C++20

Author: JohanMabille

CMakeLists.txt

@@ -77,6 +77,8 @@ target_include_directories(xtensor-blas
     $<BUILD_INTERFACE:${XTENSOR_BLAS_INCLUDE_DIR}>
     $<INSTALL_INTERFACE:include>)
 
+target_compile_features(xtensor-blas INTERFACE cxx_std_20)
+
 OPTION(CXXBLAS_DEBUG "print cxxblas debug information" OFF)
 OPTION(XTENSOR_USE_FLENS_BLAS "use FLENS generic implementation instead of cblas" OFF)
 # Decide whether to use OpenBLAS or not.
@@ -104,6 +106,8 @@ OPTION(BUILD_BENCHMARK "xtensor-blas test suite" OFF)
 OPTION(DOWNLOAD_GTEST "download gtest and build from source" OFF)
 OPTION(DOWNLOAD_GBENCHMARK "download google benchmark and build from source" OFF)
 
+OPTION(CPP23 "enables C++23 (experimental)" OFF)
+
 if(DOWNLOAD_GTEST OR GTEST_SRC_DIR)
     set(BUILD_TESTS ON)
 endif()

test/CMakeLists.txt

@@ -33,27 +33,27 @@ string(TOUPPER "${CMAKE_BUILD_TYPE}" U_CMAKE_BUILD_TYPE)
 
 include(set_compiler_flag.cmake)
 
-if(CPP20)
+if(CPP23)
   # User requested C++20, but compiler might not oblige.
   set_compiler_flag(
     _cxx_std_flag CXX
-    "-std=c++20"  # this should work with GNU, Intel, PGI
-    "/std:c++20"  # this should work with MSVC
+    "-std=c++23"  # this should work with GNU, Intel, PGI
+    "/std:c++23"  # this should work with MSVC
   )
   if(_cxx_std_flag)
-    message(STATUS "Building with C++20")
+    message(STATUS "Building with C++23")
   endif()
 else()
   set_compiler_flag(
     _cxx_std_flag CXX REQUIRED
-    "-std=c++17"  # this should work with GNU, Intel, PGI
-    "/std:c++17"  # this should work with MSVC
+    "-std=c++20"  # this should work with GNU, Intel, PGI
+    "/std:c++20"  # this should work with MSVC
   )
-  message(STATUS "Building with C++17")
+  message(STATUS "Building with C++20")
 endif()
 
 if(NOT _cxx_std_flag)
-  message(FATAL_ERROR "xtensor-blas needs a C++17-compliant compiler.")
+  message(FATAL_ERROR "xtensor-blas needs a C++20-compliant compiler.")
 endif()
 
 if(CMAKE_CXX_COMPILER_ID MATCHES "GNU" OR (CMAKE_CXX_COMPILER_ID MATCHES "Intel" AND NOT WIN32))