[Uuu-devel] function conventions

[Phil F. <da...@xg...>]

There is a general opinion that we should not destroy the registers for the
sake of easier development.

The convention that has been proposed:

on error: CF = 1 and EAX = error code
on sucess: any registers that do not have return values are unmodified

Also, if EAX is to have an error code on failure it need not be saved in the
case of sucess. Also, the registers that have return values need not be saved
in the case of sucesses. In other words, any register that does not have a
return value in either the case of error or sucess is returned unmodified in
both cases.

Now of course, this is not a stone policy. For some functions it may not be
required to save any of the registers at all, such as functions that are
usually called from places where there's nothing in the registers to save.
In other words, use your best judgement.

In my code, rather than listing every single register and it's value on call
and return, I only list the significant registers on call and I use the
shorthand "errors as usual" to denote the CF=1 on error, EAX=error code,
registers with returned values=unmodified convention, and "registers saved
as usual" to denote the convention proposed above. Remember that not all
functions return an error; many are so simple they cannot fail (and in this
case EAX would be saved, unless it has a return value).

So, tell me what you think of this; if it's accepted i'll put it in the Uuu docs
somewhere. As for the functions we have now, just change them over next time
you have the file open; there is no immediate need to convert everything.