Address Error Exception

On the Nintendo 64's CPU, the VR4300 can throw an Address Error Exception. This occurs when lookup to an invalid or non-existent address occurs, most commonly as a null-reference exception.

Exploits

Because the exception only occurs on the N64 and not the Wii VC it could potentially be exploited. The Wii VC will skip the write or read when the exception would occur. This means that a read from an invalid address into a register will actually leave the register untouched with its last value and resume normal execution.

We can then analyze crashes that cause Address Error Exceptions.

Cause	ACE Exploitable	Any Exploitable	Notes
Exceed the object limit	No	No	There's a `while (1) ;` that prevents this from occuring
Have too many objects at once on the screen
Walking at PU speed for only a portion of the 4 quarter steps on a frame
Moving at PU speed with no joystick input for all 4 quarter steps on a frame
Moving at PU speed directly into a wall
Deleting a non-existent file on the File Select Screen			sMainMenuButtons[MENU_BUTTON_ERASE_FILE_A + sSelectedFile] (assignment) is NULL. For selecting 'NO' this results in the button zoom being unaffected. 'YES' is more complex.
Moving a shadow above surface 12 while it's over OOB
Killing a Monty Mole remotely	No	No	o->oMontyMoleCurrentHole->oMontyMoleHoleCooldown = 30 causes crash as mario needs to be < 1500 units for monty to select a hole (otherwise it's null)
Killing an uninitialized Monty Mole	No	No	(same as above)
Going out of bounds in a room with a painting	No	Maybe?	`D_8035FF90` is set to t4
Being pushed off of a hang-able ceiling while in the idle hanging action	No	Doubtful	t9 for start hang. Would potentially cause Mario to stay hanging for a single frame without a ceiling, No effect for idle loop hang t8, last use of t8 set is jr t8 which is never the hang-able value 0x05)
Sound glitch	N/A	N/A	Since sound glitch only exists on the original Japanese N64 version, which wasn't released in Wii VC, this cannot be used or exploited in Wii VC legitimately