Fixed OSX build

Author: JohanMabille

.github/workflows/osx.yml

@@ -39,7 +39,7 @@ jobs:
       run: micromamba install 'openblas==0.3.29=openmp*' blas-devel
 
     - name: Configure using CMake
-      run: cmake -Bbuild -DCMAKE_CXX_STANDARD=17 -DBUILD_TESTS=ON -DCMAKE_PREFIX_PATH=$CONDA_PREFIX -DCMAKE_SYSTEM_IGNORE_PATH=/usr/lib
+      run: cmake -Bbuild -DBUILD_TESTS=ON -DCMAKE_PREFIX_PATH=$CONDA_PREFIX -DCMAKE_SYSTEM_IGNORE_PATH=/usr/lib
 
     - name: Build
       working-directory: build

CMakeLists.txt

@@ -8,8 +8,19 @@
 ############################################################################
 
 cmake_minimum_required(VERSION 3.29)
+
+# Otherwise adds std=gnu++17 on OSX ...
+set(CMAKE_CXX_EXTENSIONS OFF)
+
 project(xtensor-blas)
 
+# Otherwise adds flags for C++11 standard on OSX ...
+if(NOT CMAKE_CXX_STANDARD)
+    set(CMAKE_CXX_STANDARD 20)
+endif()
+message(STATUS "🔧 C++ standard: ${CMAKE_CXX_STANDARD}")
+
+
 set(INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/include)
 set(XTENSOR_BLAS_INCLUDE_DIR ${INCLUDE_DIR})