This core (as well as many other Arduino cores) ships with GCC `7.2.1 20170904`. ```bash ~/.arduino15/packages/arduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-g++ --version arm-none-eabi-g++ (GNU Tools for Arm Embedded Processors 7-2017-q4-major) 7.2.1 20170904 (release) [ARM/embedded-7-branch revision 255204] ``` Meanwhile `arduino-pico` uses GCC 12 and [stm32duino](https://github.com/stm32duino/Arduino_Core_STM32) uses GCC 10 (at least). I suggest updating tooling to GCC 12.