From fa704d50f70e2ead66f34594023aebb50714926c Mon Sep 17 00:00:00 2001
From: Kornel Benko <kornel@lyx.org>
Date: Mon, 5 Apr 2021 11:14:13 +0200
Subject: [PATCH] Cmake build: Omit use -f '-Wno-deprecated-copy' on compilers
 which do not support this flag.

Patch from P. De Visschere

Citing Patrick: As is stands the patch unsets the test-variable
from the cache and the test is performed for each cmake-run.
Otherwise after running cmake once the check is never run again, until
one throws away the cmakecache.txt, which I try to avoid.
I suppose that after time this check will be forgotten and if the issue
is solved (by an upgrade of the Apple clang compiler) this will pass
unnoticed.
---
 CMakeLists.txt | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index e4ed8cfc11..c3eed1a52d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -699,7 +699,14 @@ else()
 	# The following setting with LYX_GCC11_MODE is needed because cmake does not honor
 	# CMAKE_CXX_STANDARD while performing tests like
 	# check_cxx_source_compiles("..." HAVE_DEF_MAKE_UNIQUE)
-	set(LYX_CXX_FLAGS "-Wall -Wextra -Wno-deprecated-copy ${LYX_GCC11_MODE}${LYX_CXX_FLAGS}")
+	include(CheckCXXCompilerFlag)
+	unset(CHECK_WNODEPRECATEDCOPY_FLAG CACHE)
+	CHECK_CXX_COMPILER_FLAG("-Wno-deprecated-copy" CHECK_WNODEPRECATEDCOPY_FLAG)
+	if(${CHECK_WNODEPRECATEDCOPY_FLAG})
+		set(LYX_CXX_FLAGS "-Wall -Wextra -Wno-deprecated-copy ${LYX_GCC11_MODE}${LYX_CXX_FLAGS}")
+	else()
+		set(LYX_CXX_FLAGS "-Wall -Wextra ${LYX_GCC11_MODE}${LYX_CXX_FLAGS}")
+	endif()
 	if(LYX_STDLIB_DEBUG)
 	  set(LYX_CXX_FLAGS "${LYX_CXX_FLAGS} -D_GLIBCXX_DEBUG -D_GLIBCXX_DEBUG_PEDANTIC")
         else()