From ae88ef182324f79738bee5519387fe13ae7b25b2 Mon Sep 17 00:00:00 2001
From: Sergei Golubchik <serg@mariadb.com>
Date: Thu, 10 Nov 2022 00:22:15 +0100
Subject: [PATCH] use system boost, if possible

boost 1.71.0 is what ubuntu focal has, so let's start with that version.
boost 1.77.0 is the first that supports c++20
---
 CMakeLists.txt    | 7 ++++++-
 cmake/boost.cmake | 5 +++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b85bae3e1..c21a83c7b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -32,7 +32,12 @@ INCLUDE(check_compiler_flag)
 INCLUDE(ExternalProject)
 INCLUDE(CheckCXXSourceCompiles)
 
-MY_CHECK_CXX_COMPILER_FLAG("-std=c++20")
+FIND_PACKAGE(Boost 1.71.0 COMPONENTS chrono filesystem program_options regex system thread)
+
+IF (NOT Boost_FOUND OR Boost_VERSION VERSION_GREATER 1.76.99)
+  MY_CHECK_CXX_COMPILER_FLAG("-std=c++20")
+ENDIF()
+
 IF (have_CXX__std_c__20)
   SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++20")
 ELSE()
diff --git a/cmake/boost.cmake b/cmake/boost.cmake
index 534e72110..66a26670c 100644
--- a/cmake/boost.cmake
+++ b/cmake/boost.cmake
@@ -1,3 +1,8 @@
+if (Boost_FOUND)
+  add_custom_target(external_boost)
+  return()
+endif()
+
 include(ExternalProject)
 
 if(CMAKE_CXX_COMPILER_ID MATCHES "GNU")