dumb question about libgl.a and openwin()...

[Cameron Simpson,Uhmmm..???? Who knows]

I have a program which does simple things, like opening
a few windows and scribbling in them. If I compile it
on a 4D and run it there, fine. Likewise for compiling
on a PI and running it there. When I try to run the
4D verion on the PI it says
	Unable to map GM DRAM: No such device

When I try to run the PI version on the 4D it says
	Unable to map FIFO: No such device

The code in question reads like
	[...]
	prefposition(...);
	openwin("dummy");
It dies in the openwin().

I'm obviously missing something extremely basic here.
How do I make a binary which will run on both?
	- Cameron Simpson
	  cameron at spectrum.cs.unsw.oz.au