CMake: Section about Qt 5.7 and standard versions

Change-Id: Ib1ef76fc37528a6057d7b7ed96353c6a46453b94
Task-Id: QTBUG-53002
Reviewed-by: Stephen Kelly <steveire@gmail.com>

2 files changed, 12 insertions, 0 deletions

diff --git a/doc/src/development/cmake-manual.qdoc b/doc/src/development/cmake-manual.qdoc
index be486c5d..672c838c 100644
--- a/doc/src/development/cmake-manual.qdoc
+++ b/doc/src/development/cmake-manual.qdoc
@@ -105,6 +105,14 @@
     \c{CMake} version older than 3.1.0, you need to add the needed \c{-std=...} to the targets
     linking against Qt5 modules yourself.
 
+    If you use Qt 5.7 and a \c{CMake} version above 3.1.0, plus require a more recent C++ standard
+    version, use the CMake way of selecting the standard version, or specify features required and
+    let CMake compute the flags. Example:
+
+    \snippet snippets/cmake/CMakeLists.pro 6
+
+    Also see: \l{https://cmake.org/cmake/help/v3.1/manual/cmake-compile-features.7.html}{CMake cmake-compile-features Documentation}
+
     \section2 Using Qt 5 with \c{CMake} older than 2.8.12
 
     It is also necessary when using an older \c{CMake} to add Qt5<Module>_EXECUTABLE_COMPILE_FLAGS to
diff --git a/doc/src/snippets/cmake/CMakeLists.pro b/doc/src/snippets/cmake/CMakeLists.pro
index efdf4226..e938ce88 100644
--- a/doc/src/snippets/cmake/CMakeLists.pro
+++ b/doc/src/snippets/cmake/CMakeLists.pro
@@ -78,3 +78,7 @@ foreach(plugin ${Qt5Network_PLUGINS})
   message("Plugin ${plugin} is at location ${_loc}")
 endforeach()
 #! [5]
+
+#! [6]
+set(CMAKE_CXX_STANDARD 14)
+#! [6]