From:	CRDGW2::CRDGW2::MRGATE::"SMTP::CRVAX.SRI.COM::RELAY-INFO-VAX"  5-OCT-1989 09:34
To:	MRGATE::"ARISIA::EVERHART"
Subj:	Producing a debug-version of an executable file

Message-Id:  <8910051305.AA09677@crdgw1.ge.com>
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Date: Thu, 5 Oct 89 11:21 GMT+1
From: "P.L. Montessoro * CENS-CNR * +39-11-556.7013" <PIERLUCA%ITOPOLI.BITNET@CUNYVM.CUNY.EDU>
Subject: Producing a debug-version of an executable file
To: INFO-VAX@KL.SRI.COM
X-Vms-To: @[.DIS]INFOVAX



Hello to everybody.

E.Heuser-Hofmann  (CHWEYRIC@DKNKURZ1.BITNET) proposed the following solution
to force an executable image file to run with the VMS debugger:

> patch/abs xxx.exe
>   exa 20
> if 20 = 01000028 then:
>   dep 20 = 01000029
>   update
>   exit

It  seems  not  to  work  if  the  executable file has been linked using the
/NODEBUG/NOTRACEBACK options: in such  a  case  the  entry  address  of  the
debugger is missed.

I  couldn't find any documentation about the debug information in the header
of the .EXE files, but it is possible to  understand  enough  comparing  the
dump  of  two  test  files, one linked with the  /DEBUG option, and the oter
one with /NODEBUG/NOTRACEBACK.

The  following  C program modifies the header in order to insert the missing
information. It runs under VMS 5.1, I don't remember if it is  the  original
one that I wrote for VMS 4.7, of if I had to upgrade it.


****************************************************************************

#include <stdio.h>

main()

{

   int fp, fpout;
   char filename[32];
   char buffer [512];
   int cnt;

   printf ("\nfilename (without extension): ");
   scanf ("%s", filename);
   strcat (filename, ".exe");

   if ((fp = open (filename,0)) == -1)
   {
      printf ("open error\n");
      exit(4);
   }
   fpout = creat (filename,0,"mrs=512","rfm=fix","bls=512");

   read (fp, buffer, 512);

   buffer [52] = buffer [48];
   buffer [53] = buffer [49];
   buffer [54] = buffer [50];
   buffer [55] = buffer [51];

   buffer [48] = 0x68;
   buffer [49] = 0xDF;
   buffer [50] = 0xFE;
   buffer [51] = 0x7F;

   buffer [32] = 0x29;
   buffer [68] = 0x42;

   write (fpout, buffer, 512);

   while (read (fp, buffer, 512))
   {
      write (fpout, buffer, 512);
   }

   close (fp);
   close (fpout);

}

****************************************************************************


Pier Luca MONTESSORO
CENS-CNR
Dipartimento di Automatica e Informatica
Politecnico di Torino
Corso Duca degli Abruzzi 24
10129 Torino
ITALY

Tel.   011-556.7013 (Int. + 39-11-556.7013)
Fax.   011-556.7099 (Int. + 39-11-556.7099)
Telex. 220646 POLITO I

Bitnet:       pierluca@itopoli.bitnet
Span/Physnet: 39494::PIERLUCA