MicroC/OS-II hangs after printf in main

Thanks for doing a lot of the work tracking down a minimum case where it stops working. Does this same code work in a HAL only project?

Does it work if you step over the printf lots of times rather than letting it run? Where it the processor stuck if you press pause in the debugger?

I wonder whether this is something to do with event flags. When the UART driver's buffer fills up it waits on an event (ALT_FLAG_PEND in altera_avalon_uart.c).

In the HAL only case this turns into a busy loop.

In the uCOS-II case this uses the event flag mechanism built into the OS. But you haven't started the OS yet (by calling OSStart) so the event flags may not work correctly (I haven't looked at the code yet).