You're probably looking for something like this. Newlib is the libc in play here. Not exactly what you're asking for, but adjacent at least. https://interrupt.

You're probably looking for something like this. Newlib is the libc in play here. Not exactly what you're asking for, but adjacent at least. https://interrupt.memfault.com/blog/memcpy-newlib-nano https://interrupt.memfault.com/blog/memcpy-newlib-nano