I have some old Macs that I would like to remove their clock batteries so that I don't have to worry about them leaking and destroying logic boards. That being said I do want to operate them from time to time.

I've been toying around with the idea of writing a system extension to address some of the issues that come from having no battery in a Mac. In fact, I've already gotten started.

My goal is to create a system extension that detects if the date is set to something prior to 2016, and pops up a dialog on startup asking for the time and date. I would install this on 68k machines from the SE onward. So I'm shooting for System 6 compatibility.

I've purchased a copy of Inside Macintosh (volumes I through VI) on amazon and I've managed to write a program that opens a dialog asking for the time and date, which in turn sets the system clock and then quits. I could drop this in the startup folder but I REALLY want to do this as a system extension. I've managed to convert it to an INIT resource but when it runs on startup it just bombs and I have to disable it (bus error).

My understanding is that a bus error happens when a pointer points to an address outside of the available memory. so this has something to do with the system environment during startup. Does anyone know what I should do to debug this?


Turns out the solution was to open ResEdit and lock the INIT resource within my compiled extension. Everything worked as expected after doing this.


The usual way to debug a program is with a debugger. The usual low-level debugger for classic MacOS was MacsBug. I've never tried using it to debug an extension during startup, but I see no reason why it wouldn't work.

As for the specific cause of your bug, I'm guessing you're trying to use the windowing system before it's been initialized.

  • The window opens and displays correctly, the bus error occurs after the window is open.
    – denodster
    Nov 8 '16 at 17:09

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