Patch for xeus-gp: Require C++17

[Matthias Koeppe <mkoeppe@ucdavis.edu>]

This fixes a build error on macOS with Apple clang

>From 5c8f25a36c779240ad87676c739fe8e0672f24dd Mon Sep 17 00:00:00 2001
From: Matthias Koeppe <mkoeppe@math.ucdavis.edu>
Date: Wed, 6 Aug 2025 00:13:48 -0700
Subject: [PATCH 2/2] CMakeLists.txt: Do not overwrite std=c++17 with std=c++14

---
 CMakeLists.txt | 19 ++-----------------
 1 file changed, 2 insertions(+), 17 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index c8e2409..f0ff526 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -122,21 +122,6 @@ macro(xeus_gp_set_common_options target_name)
         target_compile_options(${target_name} PUBLIC /wd4018 /wd4267
/wd4715 /wd4146 /wd4129)
     endif ()

-    if (CMAKE_CXX_COMPILER_ID MATCHES "Clang" OR
-        CMAKE_CXX_COMPILER_ID MATCHES "GNU" OR
-        CMAKE_CXX_COMPILER_ID MATCHES "Intel")
-
-        target_compile_options(${target_name} PUBLIC
-Wunused-parameter -Wextra -Wreorder)
-
-        # C++14 flag
-        CHECK_CXX_COMPILER_FLAG("-std=c++14" HAS_CPP_14_FLAG)
-        if (HAS_CPP_14_FLAG)
-            target_compile_features(${target_name} PRIVATE cxx_std_14)
-        else ()
-            message(FATAL_ERROR "Unsupported compiler -- xeus-gp
requires C++14 support!")
-        endif ()
-    endif ()
-
     if (APPLE)
         set_target_properties(${target_name} PROPERTIES
             MACOSX_RPATH ON
@@ -189,7 +174,7 @@ macro(xeus_gp_create_target target_name linkage output_name)

     target_compile_definitions(${target_name} PUBLIC "XEUS_GP_EXPORTS")

-    target_compile_features(${target_name} PRIVATE cxx_std_14)
+    target_compile_features(${target_name} PRIVATE cxx_std_17)

     target_include_directories(${target_name}
                                PUBLIC
@@ -243,7 +228,7 @@ endif ()
 if (XEUS_GP_BUILD_EXECUTABLE)
     find_package(xeus-zmq ${xeus-zmq_REQUIRED_VERSION} REQUIRED)
     add_executable(xeus-gp ${XEUS_GP_MAIN_SRC})
-    target_compile_features(xeus-gp PRIVATE cxx_std_14)
+    target_compile_features(xeus-gp PRIVATE cxx_std_17)
     xeus_gp_set_common_options(xeus-gp)
     xeus_gp_set_kernel_options(xeus-gp)
     target_link_libraries(xeus-gp PRIVATE xeus-zmq)
-- 
2.47.0


-- 
Matthias Koeppe -- http://www.math.ucdavis.edu/~mkoeppe