Are the program's extents available to the g-code?

I'm working on carving a piece that's really a little too big for my mill.  It barely fits if I rotate it 45 degrees, and carve it that way.  But the size and rotation make it hard to be sure no movement will exceed the machine limits, and sure enough, about halfway through a carving (a draft practice run, happily), I tripped a limit switch.

(I should clarify that my machine is "homeless".  "home" is always relative to the piece, so there's no way for the interpreter to know in advance that I'll be exceeding a limit.)

Are the program's extents (min/max X, min/max Y) available in variables that could be used by a canned subroutine?  I did a quick skim of the source, but didn't find anything obvious.

I see why that should work.

The problem is that, because the machine is homeless, I set the soft limits to about twice as much as I actually have. This means I can home wherever I like, then set up G54, and it just works, without ever having to move to an actual home position on startup. And I can usually tell if my carve will exceed limits, so it's usually not an issue.

I'll think about changing that workflow.

I wish y'all had been around when I first configured my machine... 20 years ago.

After Tommy's first reply, I did some reading, and realized that since I have X and Y limits, configuring them as homing inputs as well would be trivial. And so it was, plus or minus a "+" or "-", here and there.

I think I never thought there was any point to having a true home, and really, I've gotten by without it until now. I hit the limit switches when jogging reasonably often, but they're soft-mounted, so it's not a big deal.

In any case, I'm fully configured with home+limits on X and Y now, and I have proper soft limits configured, so I'm all set. <Another high five!>

Secondary question: I don't have a Z+ limit switch. My mill is so slow I'd really have to not be paying attention for the carriage to get close to the stepper. A lower limit would be nice, but I really don't understand how that could work. My spindle is a router, so the bit length varies a lot. Is there any way to configure this to work? I see people say that they don't bother with a lower Z limit, and just rely on a soft limit there, but what would you set it to? Is there something about "real" spindles that I don't know? Are the bits always the same length?