From 59f64d8d8207a7cd6162cf02f78a6757eb2143f5 Mon Sep 17 00:00:00 2001
From: Bernd Amend <bernd.amend@gmail.com>
Date: Sat, 22 May 2021 14:48:12 +0200
Subject: [PATCH] set min required cmake version to 3.12

The already used functionallity already
requires a more recent cmake version.
Short summary why a never version is required:
  CMAKE_CXX_STANDARD requires >=3.1
  CMAKE_COMPILER_IS_GNUCC requires >3.7
  ENABLE_LTO can be simplified with >3.11 (3.13 VS)
---
 CMakeLists.txt | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index c1510810..54e25c4c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,12 +1,12 @@
-cmake_minimum_required(VERSION 2.8)
-
-if(NOT ${CMAKE_VERSION} VERSION_LESS "3.1")
-  cmake_policy(SET CMP0054 NEW)
-endif()
+cmake_minimum_required(VERSION 3.12)
+cmake_policy(SET CMP0054 NEW)
 
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
+# required since cmake 3.4 at least for libc++
+set(CMAKE_ENABLE_EXPORTS ON)
+
 project(chaiscript)
 
 option(MULTITHREAD_SUPPORT_ENABLED "Multithreaded Support Enabled" TRUE)
@@ -62,10 +62,9 @@ if(CMAKE_COMPILER_IS_GNUCC OR "${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
   endif()
 
   option(ENABLE_LTO "Enable Link Time Optimization" FALSE)
-
-  if (ENABLE_LTO)
-    add_definitions(-flto)
-    set(LINKER_FLAGS "${LINKER_FLAGS} -flto")
+  if(ENABLE_LTO)
+    check_ipo_supported()
+    set(CMAKE_INTERPROCEDURAL_OPTIMIZATION TRUE)
   endif()
 
   option(GPROF_OUTPUT "Generate profile data" FALSE)