You’re the one who decided to start splitting hairs. Flounce on away.

Turning on an LED when it’s dark doesn’t require a microcontroller, let alone a Cortex-M. You can accomplish that with analog electronics.

Anyway, you’re moving the goalposts all over the place. What happened to the RTOS kernel from earlier?

Yes, and this is ignoring interrupts, access privileges, thread stacks … what’s the C equivalent of the MSR and MRS instructions?

My point is that there’s still gonna be some somewhere. You’re just trying to handwave it away because somebody else wrote it.

You’re just describing more components that are written in C and assembly.

True, but you’re not gonna be setting the access levels or doing anything else with control registers on a Correx-M in pure C, let alone boot to a safe state with zeroed registers.

Hell, assembly code is still necessary for the lowest-level init code. Once you have a functional stack and some var init logic you can graduate to C.