Genesis core doesn't reset everything properly

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Open ROM provided in attachment
2. Select Sonic Only (No Save)
3. It should pull up a corrupted level select screen.  Select Carnival Night 
Zone act one and wait for it to crash.
4.  Attempt a hard reset.

What is the expected output? What do you see instead?
Should reset and run the ROM.

What version of the product are you using? On what operating system?
SVN r7603

(Yes, this is a corrupted ROM, but the behavior is still incorrect)

Original issue reported on code.google.com by Reaper.m...@gmail.com on 17 Aug 2014 at 3:27

Attachments:

• [s3andk (10 knuckles, get into lava reef and others).bin](https://storage.googleapis.com/google-code-attachments/bizhawk/issue-253/comment-0/s3andk %2810 knuckles, get into lava reef and others%29.bin)

[alyosha-tas]

Somehow this ROM is attempting (and succeeding) to write to ROM space. Addresses starting at 00061A are changed after the level is selected. They are not changed back as part of loading the state (obviously not expecting this region of memory to be swappable.)

The trace logger crashes on me when I attempt to use it to figure out exactly what's happening, but this is the basic explanation of the problem.

EDIT: I removed some exceptions in the trace logger, and with that its pretty obvious that the stack is getting set to ROM space and the writes to the stack are not being checked to be writable, it just automatically assumes it is. Two solutions seem to be to add the complete system bus to the save state, or check every stack write to make sure it is valid.