Thank you for the fast response !
I use “-std=gnu++14”. When i change to “-std=c++14” Clang itellisense works correctly (including the .h header files).
There is another old bug in “VisualGDB Project Properties”->”Embedded Project”. I have a standalone project and would like to use VisualGDB build variables (e.g. “$(ProjectDir)”) in the “include directories” and in the “linker script” settings. This doesn’t work.