From 112208ddd9c862d2788f28dadf8ac7073f1553eb Mon Sep 17 00:00:00 2001
From: Kornel Benko <kornel@lyx.org>
Date: Thu, 24 Oct 2024 11:35:06 +0200
Subject: [PATCH] Amend c916bd15 for cmake build: Require C++17

---
 development/cmake/modules/FindCXX11Compiler.cmake | 3 ++-
 development/cmake/modules/LyXMacros.cmake         | 6 +++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/development/cmake/modules/FindCXX11Compiler.cmake b/development/cmake/modules/FindCXX11Compiler.cmake
index 750a8ff32b..ddab3a2335 100644
--- a/development/cmake/modules/FindCXX11Compiler.cmake
+++ b/development/cmake/modules/FindCXX11Compiler.cmake
@@ -38,7 +38,8 @@ INCLUDE(FindPackageHandleStandardArgs)
 # Detection of c++20 works well, but our code is not ready for it yet.
 # We currently get errors with internal boost and also from our code.
 set(_max_std_num 20)
-lyxgetknowncmakestd(${_max_std_num} tmpnums)
+set(_min_std_num 17)
+lyxgetknowncmakestd(${_max_std_num} ${_min_std_num} tmpnums)
 
 if (CMAKE_CXX_COMPILER_ID MATCHES "^([cC]lang|AppleClang)$")
   foreach(_num ${tmpnums})
diff --git a/development/cmake/modules/LyXMacros.cmake b/development/cmake/modules/LyXMacros.cmake
index 045a63f31a..16b95c4ef2 100644
--- a/development/cmake/modules/LyXMacros.cmake
+++ b/development/cmake/modules/LyXMacros.cmake
@@ -468,12 +468,12 @@ function(determineversionandbuildtype configfile package version dirs date build
 endfunction(determineversionandbuildtype)
 
 # determine known cmake cxx_std features but only if not greater than ${max_desired}
-function(lyxgetknowncmakestd max_desired result)
+function(lyxgetknowncmakestd max_desired min_enabled result)
   set(tmp_list)
   set(CXX_STD_LIST)
   math(EXPR max_desired "${max_desired}+1")
   if (CMAKE_VERSION VERSION_LESS "3.9")
-    list(APPEND tmp_list 98 11 14)
+    list(APPEND tmp_list 14 17 20)
   else()
     foreach(_e ${CMAKE_CXX_COMPILE_FEATURES})
       if (_e MATCHES "^cxx_std_\(.*)")
@@ -484,7 +484,7 @@ function(lyxgetknowncmakestd max_desired result)
   list(REVERSE tmp_list)
   # Filter undesired from list
   foreach(i ${tmp_list})
-    if (i LESS ${max_desired} OR i GREATER 89)
+    if (i LESS ${max_desired} AND i GREATER_EQUAL ${min_enabled})
       list(APPEND CXX_STD_LIST ${i})
     endif()
   endforeach()