From cd8bb671321b5163c21f84689f929b671ed68750 Mon Sep 17 00:00:00 2001
From: Paul Zander <negril.nx+gentoo@gmail.com>
Date: Mon, 20 Oct 2025 21:26:47 +0200
Subject: [PATCH] cxx standard 17

Signed-off-by: Paul Zander <negril.nx+gentoo@gmail.com>

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 80d36b991..8106bb264 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -330,11 +330,8 @@ if (EIGEN_BUILD_TESTING)
 
   option(EIGEN_TEST_CXX11 "Enable testing with C++11 and C++11 features (e.g. Tensor module)." ${EIGEN_COMPILER_SUPPORT_CPP11})
   if(EIGEN_TEST_CXX11)
-    set(CMAKE_CXX_STANDARD 11)
+    set(CMAKE_CXX_STANDARD 17)
     set(CMAKE_CXX_EXTENSIONS OFF)
-    if(EIGEN_COMPILER_SUPPORT_CPP11)
-      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
-    endif()
   else()
     ei_add_cxx_compiler_flag("-std=c++03")
   endif()
@@ -373,7 +370,7 @@ if (EIGEN_BUILD_TESTING)
     ei_add_cxx_compiler_flag("-Wshorten-64-to-32")
     ei_add_cxx_compiler_flag("-Wlogical-op")
     ei_add_cxx_compiler_flag("-Wenum-conversion")
-    ei_add_cxx_compiler_flag("-Wc++11-extensions")
+    # ei_add_cxx_compiler_flag("-Wc++11-extensions")
     ei_add_cxx_compiler_flag("-Wdouble-promotion")
     # ei_add_cxx_compiler_flag("-Wconversion")
     ei_add_cxx_compiler_flag("-Wshadow")
diff --git a/doc/special_examples/CMakeLists.txt b/doc/special_examples/CMakeLists.txt
index a0267a512..d7fc80976 100644
--- a/doc/special_examples/CMakeLists.txt
+++ b/doc/special_examples/CMakeLists.txt
@@ -23,7 +23,6 @@ if(EIGEN_COMPILER_SUPPORT_CPP11)
   add_executable(random_cpp11 random_cpp11.cpp)
   target_link_libraries(random_cpp11 ${EIGEN_STANDARD_LIBRARIES_TO_LINK_TO} Eigen3::Eigen)
   add_dependencies(all_examples random_cpp11)
-  target_compile_options(random_cpp11 PRIVATE "-std=c++11")
 
   add_custom_command(
     TARGET random_cpp11
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 7ce260e0e..f503efc5d 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -386,7 +386,6 @@ if(CUDA_FOUND AND EIGEN_TEST_CUDA)
   string(REPLACE "-fno-check-new" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
 
   if(EIGEN_TEST_CUDA_CLANG)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
     string(APPEND CMAKE_CXX_FLAGS " --cuda-path=${CUDA_TOOLKIT_ROOT_DIR}")
     foreach(GPU IN LISTS EIGEN_CUDA_COMPUTE_ARCH)
       string(APPEND CMAKE_CXX_FLAGS " --cuda-gpu-arch=sm_${GPU}")
diff --git a/unsupported/test/CMakeLists.txt b/unsupported/test/CMakeLists.txt
index 1d5e9b174..cf394de86 100644
--- a/unsupported/test/CMakeLists.txt
+++ b/unsupported/test/CMakeLists.txt
@@ -227,7 +227,6 @@ if(CUDA_FOUND AND EIGEN_TEST_CUDA)
   string(REPLACE "-ansi" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
 
   if(EIGEN_TEST_CUDA_CLANG)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
     string(APPEND CMAKE_CXX_FLAGS " --cuda-path=${CUDA_TOOLKIT_ROOT_DIR}")
     foreach(ARCH IN LISTS EIGEN_CUDA_COMPUTE_ARCH)
         string(APPEND CMAKE_CXX_FLAGS " --cuda-gpu-arch=sm_${ARCH}")
-- 
2.51.1