in your ARM compiler 5 / IDE, Go to Project => Options for Target => C/C++ (AC6) tab. Make sure short enums/wchar is enabled. This is equivalent to the command line option, -fshort-enums -fshort-wchar. Using the smaller sizes will help conserve memory in the application, and the last option agrees with the size of wchar_t in the prebuild libraries.
more could be found here: https://www.keil.com/support/docs/3975.htm