Int21 : Dont reset systematically CFLAG

Jukka Heinonen jhei at
Fri Aug 22 04:54:28 CDT 2003

On Fri, Aug 22, PETREOLLE Sylvain wrote:
> Doing some research in int21.c shows that many functions that rely on CFLAG
> dont set it when they are in error state.
> IMHO many DOS programs are already broken today since these functions 
> appear to be successfull at every moment.
> For example : INT21_FileDateTime (handler for function 0x57, file
> attributes)

Yes, it is highly likely that there are lots of small bugs in
DOS interrupt handling. If you want to work on fixing those bugs,
feel free to do so. However, do not submit patches that break
those interrupt subfunctions that work correctly now, even if 
the reason they work is due to some broken workaround.

What I would suggest is:
- Submit one or more patches that make each
  winedos/int21.c subfunction (even those that call msdos/int21.c)
  that is supposed to modify CFLAG modify the flag explicitly.
  It is fine to make those subfunctions begin with
  RESET_CFLAG and FIXME comment about needing to fix/verify CFLAG
- After all subfunctions have been reviewed, submit a patch that
  removes the global RESET_CFLAG.

As you can see, the amount of work you need to do does not change
and you don't need to spend lots of time hunting down regressions
because you don't break those programs that happen to work due to
global RESET_CFLAG. Please, more patches, less talk.

Jukka Heinonen <>

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