@micropython.asm_thumb code fails with an internal sim error

[microbit-matt-hillsdon]

E.g.

@micropython.asm_thumb
def asm_add(r0, r1):
    add(r0, r0, r1)

print(asm_add(1, 2))

Results in:

instrument.ts:109 RuntimeError: table index is out of bounds
    at 004b255a
    at 004b255a
    at 004b255a
    at ret.<computed> (firmware.js:1948:35)
    at firmware.js:1045:22
    at invoke_iiiii (firmware.js:2459:12)
    at imports.<computed> (firmware.js:1914:35)
    at 004b255a
    at 004b255a
    at 004b255a

Ideally we'd fail cleanly saying it wasn't supported but only when the relevant code is run.

[microbit-matt-hillsdon]

Note the editor also lacks support, see microbit-foundation/python-editor-v3#774

[microbit-matt-hillsdon]

Discussed with @dpgeorge today and he'll respond here.

[dpgeorge]

You can use:

#define MICROPY_EMIT_INLINE_THUMB               (0)

to totally disable this feature.

Or try this to make it raise an exception just before executing the asm-thumb code:

#define MICROPY_MAKE_POINTER_CALLABLE(p) \
    (mp_raise_msg(&mp_type_RuntimeError, MP_ERROR_TEXT("asm_thumb code not supported"))), p