2009/7/18 Kenneth J. Davis jere...@fdos.org:
It has to deal with debugging the kernel, especially during
initialization. I choose this method as the kernel does not usually
have many strings it prints except when built with DEBUG and the
alternative is to determine exactly which portions of the C code and
corresponding strings may possibly reside in different segments at
different times (any time DS may not equal seg of string) and change
just those prints - otherwise some strings print and some print
garbage. I realize it changes printf prototype to only match
compilers in large data mode, but the kernel does not use printf from
the standard library of DOS compilers anyway. However, I will revert
the changes if you prefer.
ok, I've reverted some of the changes: I found a couple of situations:
DS == SS == DGROUP: this is normal, no problems here.
DS == DGROUP, but SS!=DS. This happens for instance in nls.c, in that
case we need to be careful by making pointers to items on the stack
FAR, and similarly for va_list/va_arg. I've kept that part of your
change, but only for resident debug printf()s. Compiling such code
with -zu helps for OW (especially also to catch warnings) but
unfortunately such a switch isn't there for TC, so we need to handle
this situation manually.
DS != DGROUP, and (perhaps) SS!=DS. This is very confusing and doesn't
even work after your change:
printf(foo) with a far format string is just compiled into a PUSH
DS/PUSH foo/CALL printf.
So we need to *always* keep DS equal to DGROUP in C code, which is why
I fixed the entry to the kernel's
int2f/ah=14 handler for NLSFUNC in nls.c.
By the way, I didn't find init code where SS!=DS, but did you find any?
Bart
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