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Date: Wed, 14 Sep 2005 08:41:11 -0400
From: =?iso-8859-1?Q?Benjamin_B=E9lisle?= <bbelisle AT jpselectronique DOT com>
Subject: RE: Help with Dos errors
In-reply-to: <43280742.sandmann@clio.rice.edu>
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Thank you for your responses.
My function that writes on the diskette looks a bit like this:

	if (F_Open ("a:\\agrimtl2.ini", WRITE)) {
		return 1;
		}
	else {
	   	EcrireINI ();
		F_Close ();
		}
	sprintf (Buff, "a:\\%u.txt", Annee);
	Fichier = fopen (Buff, "wb");
	if (Fichier == NULL) {
		return 1;
		}
	else {
	... And so on

so yes I do verify the return values.
But I also want to know why it failled, the possible error codes (_doserrno)
when writing on (a:) are:

---DOS 3.0+ (INT 24 errors)---
 13h (19)  disk write-protected
 14h (20)  unknown unit
 15h (21)  drive not ready
 16h (22)  unknown command
 17h (23)  data error (CRC)
 18h (24)  bad request structure length
 19h (25)  seek error
 1Ah (26)  unknown media type (non-DOS disk)
 1Bh (27)  sector not found
 1Ch (28)  printer out of paper
 1Dh (29)  write fault
 1Eh (30)  read fault
 1Fh (31)  general failure
 20h (32)  sharing violation
 21h (33)  lock violation
 22h (34)  disk change invalid (ES:DI -> media ID structure)(see #01681)
 23h (35)  FCB unavailable
 23h (35)  (PTS-DOS 6.51+, S/DOS 1.0+) bad FAT
 24h (36)  sharing buffer overflow
 25h (37)  (DOS 4.0+) code page mismatch
 26h (38)  (DOS 4.0+) cannot complete file operation (EOF / out of input)
 27h (39)  (DOS 4.0+) insufficient disk space

Which is why I do:

	if(_doserrno > 18 && _doserrno < 40)
 	{
    		DosError = 1;
  		TypeDosError = _doserrno-19;
  	}

Then I open a message box displaying the right error message for the user.
(Note that I could simply use the strerror(errno) function, but I display
the message in different languages, depending on the language setting.

What happens (when on the dos computer) is that the function simply aborts
without displaying any error message, so _doserrno is not between 18 and 40.
The program keeps on running normally.  Like I said, this works perfectly
when on windows.

>DJGPP doesn't use the abort,retry,fail stuff.

This is why I don't need to override the int 24 interrupt like the program
was done with Borland.

I think this may be a problem with the CWSDPMI host and int 21.  I've tried
the following code to "catch" the error with function 59h of int 21h (Thank
you dos bible) which should return the same error codes as _doserrno:

	regs.h.ah = 0x59;
	regs.d.ebx = 0;
	__dpmi_int(0x21, &regs);

	if(regs.x.ax > 18 && regs.x.ax < 40)
   	{
      	DosError = 1;
  		TypeDosError = regs.x.ax-19;
   	}

And again, works fine in Windows (which I've heard has a much better DPMI
host than CWSDPMI).

Benjamin.

-----Message d'origine-----
De : Charles Sandmann [mailto:sandmann AT clio DOT rice DOT edu]
Envoyé : 14 septembre 2005 07:20
À : djgpp AT delorie DOT com
Objet : Re: Help with Dos errors


> I want to create a file on a disk (A:) and detect any DOS errors.

Errors should always be flagged to the routine which was called.
DJGPP doesn't use the abort,retry,fail stuff.

> This works fine when I try the program in a Windows XP Dos window, but
there
> is no error detected (when for example there is no disk) when I try the
> program on a DOS Version 6.20 computer with the CWSDPMI host.

This may just be the different error code returned; the open or write
statements should be checked for failure.  You didn't say how it fails
under DOS or provide the example code doing the open.