From 9a218e92b530a19b17585cc49d3c9dc8cf4f996b Mon Sep 17 00:00:00 2001
From: Fred Hornsey <hornseyf@unityfoundation.io>
Date: Mon, 6 May 2024 17:16:52 -0500
Subject: [PATCH] Test _MSVC_LANG instead of __cplusplus for CMake

---
 cmake/init.cmake                      | 5 -----
 cmake/test_cxx_std.cpp                | 6 +++++-
 docs/news.d/cmake-ace-tao-cpp-std.rst | 9 +++++++--
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/cmake/init.cmake b/cmake/init.cmake
index b5717714f93..96f7d489075 100644
--- a/cmake/init.cmake
+++ b/cmake/init.cmake
@@ -178,15 +178,10 @@ function(_opendds_set_cxx_std)
   # Get the latest known default compiler C++ standard
   set(default_cxx_std_year 1998)
   foreach(cplusplus IN LISTS cplusplus_values)
-    set(args)
-    if(MSVC AND NOT MSVC_VERSION LESS 1914)
-      list(APPEND args CMAKE_FLAGS "-DCMAKE_CXX_FLAGS=/Zc:__cplusplus")
-    endif()
     try_compile(compiled
       "${temp_dir}/cplusplus_${cplusplus}"
       SOURCES "${test_cxx_std}"
       COMPILE_DEFINITIONS "-DOPENDDS_TEST_CPLUSPLUS=${cplusplus}L"
-      ${args}
     )
     if(compiled)
       _opendds_cplusplus_to_year(default_cxx_std_year ${cplusplus})
diff --git a/cmake/test_cxx_std.cpp b/cmake/test_cxx_std.cpp
index 969068816cb..da063eb1e2f 100644
--- a/cmake/test_cxx_std.cpp
+++ b/cmake/test_cxx_std.cpp
@@ -1,5 +1,9 @@
 #ifdef OPENDDS_TEST_CPLUSPLUS
-#  if __cplusplus < OPENDDS_TEST_CPLUSPLUS
+#  ifdef _MSVC_LANG
+#    if _MSVC_LANG < OPENDDS_TEST_CPLUSPLUS
+#      error "Less then requested value"
+#    endif
+#  elif __cplusplus < OPENDDS_TEST_CPLUSPLUS
 #    error "Less then requested value"
 #  endif
 #elif defined OPENDDS_TEST_ACE_CXX_STD
diff --git a/docs/news.d/cmake-ace-tao-cpp-std.rst b/docs/news.d/cmake-ace-tao-cpp-std.rst
index 8f52ea8444f..e582401dff9 100644
--- a/docs/news.d/cmake-ace-tao-cpp-std.rst
+++ b/docs/news.d/cmake-ace-tao-cpp-std.rst
@@ -1,5 +1,10 @@
 .. news-prs: 4618
 
 .. news-start-section: Platform Support and Dependencies
-- Fix cases where the CMake support fails when using the ACE/TAO master branch because it now requires C++17.
-.. news-end-section. news-end-section
+.. news-start-section: CMake
+- Allow using the ACE/TAO master branch which now requires C++17.
+.. news-end-section
+.. news-start-section: Building with CMake
+- Visual Studio now defaults to using at least C++11 with ACE 6/TAO 2 instead of C++03.
+.. news-end-section
+.. news-end-section