Suppose I have 8 windows like this figure: http://www.sics.se/~psm/sparcwin.gif
And I'm right in that situation, WIM points to w7, and I'm in window w0.
Suppose that in this window, I'm going to call some function that recives one parameter. So I set the parameter value to %o1 (to let the function recive it in %i0).
Ok, then I make the call, and the function does a 'save'. WIM in that window bit is 1, so a window_overflow is triggered. What I understood about this, is that the handler save on the stack of window w7 (%sp), the registers %i1,..,%i7,%l0,..,%l7, to let then 'when going back' in the window_underflow recover that window.
My question is... when the window is saved, the originals %i0,...,%i7 of w7 where lost due to now are the parameters of the function that the program in w0 called (because I set %o0,.. in w0 before calling and then make the 'save' fault). So this "system" does not make sense, so I guess I'm missing something.
Another similar question. Suppose my program in w0 does not call a function, but use %o0,%o1,.. as "local" variables, I would have the same problem without even know that I killed %i0,%i1,.. of w7.
ANSWER: I found that the invalid windows is already saved in the stack, so when the 'save' is done, the window_overflow handler would save w6 in the stack (and set WIM to w6). This obviously explains all about my question. I guess I confused myselft when seeing an handler example of this trap and not remembering that in V8 it always decrements CWP without checking WIM.
