SW4STM32 and SW4Linux fully supports the STM32MP1 asymmetric multicore Cortex/A7+M4 MPUs

   With System Workbench for Linux, Embedded Linux on the STM32MP1 family of MPUs from ST was never as simple to build and maintain, even for newcomers in the Linux world. And, if you install System Workbench for Linux in System Workbench for STM32 you can seamlessly develop and debug asymmetric applications running partly on Linux, partly on the Cortex-M4.
You can get more information from the ac6-tools website and download (registration required) various documents highlighting:

System Workbench for STM32

itoa() and utoa() have bad results

OK, finally in some common C language documentation I found, that the 3rd argument of the itoa() or utoa() represents numerical base, not the number of the characters to be converted (size). rolleyes
However the Additional question stays unanswered.
Best regards