From 34a8a9302f135495c79160184758d9251e42cb99 Mon Sep 17 00:00:00 2001
From: "alexey.lysiuk" <alexey.lysiuk@gmail.com>
Date: Sun, 18 Oct 2020 11:34:39 +0300
Subject: [PATCH] - removed obsolete probing of C++ standard for GCC and Clang

CMake try_compile() function still requires explicit command line option
---
 CMakeLists.txt     |  7 +++++++
 src/CMakeLists.txt | 24 ------------------------
 2 files changed, 7 insertions(+), 24 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8c030d66b..5dabe7bed 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -146,6 +146,13 @@ endif()
 
 if( ZD_CMAKE_COMPILER_IS_GNUCXX_COMPATIBLE )
 	set( PROFILE 0 CACHE BOOL "Enable profiling with gprof for Debug and RelWithDebInfo build types." )
+
+	if( CMAKE_CXX_STANDARD )
+		# By default, try_compile() invocations ignore CXX_STANDARD value
+		# CMake 3.8 and newer have CMP0067 policy that fixes the issue, but it should be enabled explicitly
+		# Older versions require manual specification of the corresponding command line option
+		set( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++${CMAKE_CXX_STANDARD}" )
+	endif()
 endif()
 
 # Fast math flags, required by some subprojects
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index aa18ccdfb..f7a399bdb 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -330,30 +330,6 @@ if( ZD_CMAKE_COMPILER_IS_GNUCXX_COMPATIBLE )
 		set( CMAKE_CXX_FLAGS "-DNO_SSE ${CMAKE_CXX_FLAGS}" )
 	endif()
 
-	# Use the highest C++ standard available since VS2015 compiles with C++14
-	# but we only require C++11.  The recommended way to do this in CMake is to
-	# probably to use target_compile_features, but I don't feel like maintaining
-	# a list of features we use.
-	CHECK_CXX_COMPILER_FLAG( "-std=gnu++14" CAN_DO_CPP14 )
-	if ( CAN_DO_CPP14 )
-		set ( CMAKE_CXX_FLAGS "-std=gnu++14 ${CMAKE_CXX_FLAGS}" )
-	else ()
-		CHECK_CXX_COMPILER_FLAG( "-std=gnu++1y" CAN_DO_CPP1Y )
-		if ( CAN_DO_CPP1Y )
-			set ( CMAKE_CXX_FLAGS "-std=gnu++1y ${CMAKE_CXX_FLAGS}" )
-		else ()
-			CHECK_CXX_COMPILER_FLAG( "-std=gnu++11" CAN_DO_CPP11 )
-			if ( CAN_DO_CPP11 )
-				set ( CMAKE_CXX_FLAGS "-std=gnu++11 ${CMAKE_CXX_FLAGS}" )
-			else ()
-				CHECK_CXX_COMPILER_FLAG( "-std=gnu++0x" CAN_DO_CPP0X )
-				if ( CAN_DO_CPP0X )
-					set ( CMAKE_CXX_FLAGS "-std=gnu++0x ${CMAKE_CXX_FLAGS}" )
-				endif ()
-			endif ()
-		endif ()
-	endif ()
-
 	# Remove extra warnings when using the official DirectX headers.
 	# Also, TDM-GCC 4.4.0 no longer accepts glibc-style printf formats as valid,
 	# which is a royal pain. The previous version I had been using was fine with them.