Zephyr Workbench, a VSCode extension to manage Zephyr on STM32.
It enables users to easily create, develop, and debug Zephyr applications.
Main features:
Install host dependencies.
Import toolchain and SDK.
Create, configure, build and manage apps.
Debug STM32.
You can directly download it from the VSCode marketplace
For more details, visit the Zephyr Workbench
Strange ! the double underscore are not mandatory.
You can check UART_printf example (CubeF4\Projects\STM32F401RE-Nucleo\Examples\UART\UART_Printf\SW4STM32\syscalls.c).
Note: If you are not using FreeRTOS, you do not need the stack_ptr (comment #define FreeRTOS)