STM8s template using Small Device C Complier (SDCC) and STM8S_StdPeriph_Driver libraries.
Porting StdPeriph Driver to SDCC, see more here.
NOTE: Several common libraries (e.g.:stdio.h, ctype.h, math.h, string.h, etc.), which are provided by SDCC, have been modified and no longer resemble the traditional gcc compiler. You should refer to this document before using them.