Cross-compilation (many to many)...

[Chase]

what i'm looking for are **generalized** instructions for building a  
cross-compiler on **any** platform (on which gcc can run) that  
targets **any** platform (targetable by gcc).

for example, let's say i build a special GCC on Linux that can create  
binaries for BeOS, Windows, Max OS X, or Linux:

specialgcc --target=macosx ....

i want to sit at any one of those machines in my home or office and  
build a binary that will run on any one of the other systems (or  
itself of course).

... or all of them....

specialgcc --target=beos ....
specialgcc --target=windows ....
specialgcc --target=linux ....
specialgcc --target=macosx ....

4 binaries that can be copied to and run on each of the other  
systems, compiled one right after the other on one Linux development  
machine.

where are instructions on how to do this in a very generalized way  
(not just linux to windows)?

i know that mingw is part of the solution (for targeting windows),  
but i'm still unlear (even after reading through the mingw faq and  
installation documentation) on the exact purpose of mingw.  why is  
this needed at all?  is this unique to targeting windows, or will i  
need some sort of equivelant thing for targeting BeOS or Mac OS X or  
Linux from other platforms?

If all of this is in the documentation and I just missed it, please  
provide a link to the exact page.

- chase