MSVC Changes. Leave CMake to set /std:. Only set /Zc:__cplusplus for VS2019+. Updated README.md

README.md

@@ -714,6 +714,8 @@ $ make
 
 The option -DCMAKE\_CXX\_FLAGS=-Wno-deprecated suppresses warnings from C++11 concerning auto\_ptr and other deprecated features.
 
+**Caution:** Visual Studio users should not use -DCMAKE\_CXX\_STANDARD=11 or -DCMAKE\_CXX\_FLAGS=-Wno-deprecated.
+
 [TOC](#TOC)
 
 <div id="3">
@@ -1187,4 +1189,4 @@ $ sudo pkg install developer/gcc-7
 
 [TOC](#TOC)
 
-Written by Robin Mills<br>robin@clanmills.com<br>Updated: 2020-05-02
+Written by Robin Mills<br>robin@clanmills.com<br>Updated: 2020-05-04

cmake/compilerFlags.cmake

@@ -138,35 +138,9 @@ if(MSVC)
     add_compile_options(/MP)
     add_definitions(-DNOMINMAX -DWIN32_LEAN_AND_MEAN)
     
-    # https://stackoverflow.com/questions/44960715/how-to-enable-stdc17-in-vs2017-with-cmake
-    if (MSVC_VERSION GREATER_EQUAL "1700") # VS2015 and up
-        include(CheckCXXCompilerFlag)
-        # MSVC doesn't have a setting for C++11 as it's a subset of C++14
-        if ( ${CMAKE_CXX_STANDARD} STREQUAL "11" OR ${CMAKE_CXX_STANDARD} STREQUAL "14" )
-            CHECK_CXX_COMPILER_FLAG("/std:c++14" _cpp_14)
-            if (_cpp_14)
-                add_compile_options("/std:c++14")
-            else()
-                message(WARNING "Cannot set compiler option /std:c++14")
-            endif()
-        endif()
-        if ( ${CMAKE_CXX_STANDARD} STREQUAL "17" )
-            CHECK_CXX_COMPILER_FLAG("/std:c++17" _cpp_17)
-            if (_cpp_17)
-                add_compile_options("/std:c++17")
-            else()
-                message(WARNING "Cannot set compiler option /std:c++17")
-            endif()
-        endif()
-        if ( ${CMAKE_CXX_STANDARD} STREQUAL "20" )
-            CHECK_CXX_COMPILER_FLAG("/std:c++11" _cpp_20)
-            if (_cpp_20)
-                add_compile_options("/std:c++20")
-            else()
-                message(WARNING "Cannot set compiler option /std:c++20")
-            endif()
-        endif()
-        # https://devblogs.microsoft.com/cppblog/msvc-now-correctly-reports-__cplusplus/
+    # https://devblogs.microsoft.com/cppblog/msvc-now-correctly-reports-__cplusplus/
+    if (MSVC_VERSION GREATER_EQUAL "1900") # VS2019 and up
         add_compile_options("/Zc:__cplusplus")
     endif()
+
 endif()