The needed stack size is hard to determine by the compiler. It will try,
but will fail in many common cases. Therefore, the runtime will pick a
fixed stack size.
There is a tradeoff between avoiding stack overflows and wasting RAM.
This tradeoff depends on the application: some don't need large stack
sizes but do need a lot of memory, while others need deep stacks but
aren't so memory constrained. That's why I've added a flag to do this on
the command line: https://github.com/tinygo-org/tinygo/pull/3159
It may be reasonable to use a different stack size per chip, for example
chips with lots of RAM could default to a larger stack size. But I don't
think it's a good idea to do this per board.
This can be very useful for some purposes:
* It makes it possible to disable the UART in cases where it is not
needed or needs to be disabled to conserve power.
* It makes it possible to disable the serial output to reduce code
size, which may be important for some chips. Sometimes, a few kB can
be saved this way.
* It makes it possible to override the default, for example you might
want to use an actual UART to debug the USB-CDC implementation.
It also lowers the dependency on having machine.Serial defined, which is
often not defined when targeting a chip. Eventually, we might want to
make it possible to write `-target=nrf52` or `-target=atmega328p` for
example to target the chip itself with no board specific assumptions.
The defaults don't change. I checked this by running `make smoketest`
before and after and comparing the results.
