Subj : Re: reentrant fwrite/fputc/etc ?
To   : borland.public.cpp.borlandcpp
From : gary <news@cordelli.net>
Date : Fri Nov 14 2003 01:55 pm

Ed:

thanks.  yes, i am already stack switching to avoid blowing a low-level 
OS/BIOS stack.  i've done the whole full-blown "InDOS" flag bit before, 
with complete DOS context switching, but this particular problem doesn't 
call for that kind of overhead (nor could it survive it, frankly).  i 
really just needed to dump some serial data to a file during testing and 
didn't want to hang a "monitor" PC off the side of my serial link.  was 
looking for a quick-and-dirty way to do this with fwrite() or fputc(). 
in the absense of a safe way to do this with low ISR overhead, i will 
probably just dump the data to a buffer in the ISR and then put a test 
in the foreground loop that writes the buffer out to disk when there is 
something there to dump.

Ed Mulroy [TeamB] wrote:

> No function which makes a call to DOS is stable for use in an ISR unless
> specific, non-trivial efforts are made within the ISR itself to arrange for
> the DOS call to work.  All of the FILE* I/O functions and most if not all of
> the other file I/O functions (including the ones which write as a file to
> stdout or stderr) use DOS calls.
> 
> If you need to do that I suggest that you get a book such as "Undocumented
> DOS" and use the INDOS flag, an ISR reentrancy flag and stack switching to
> arrange that it works.
> 
> .  Ed
> 
> 
>>gary wrote in message
>>news:3FB517F7.2040506@cordelli.net...
>>
>>this is why you need to be careful what C lib functions you
>>call inside an ISR.
>>
> 
>

.