DosSetExceptionHandler()      Install protected mode exception handler
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 Function : Install a protected mode exception handler

 Syntax   : USHORT BLXAPI DosSetExceptionHandler( USHORT excno, PEHANDLER
            newhandler, PEHANDLER _far *prevhandler);

 excno      Exception number (0-13).

 newhandler Pointer to new handler.

 prevhandlerPointer to a function pointer to receive the address of the
            previous exception handler.

 Return   : Address of the previous exception handler.

 DosSetExceptionHandler() installs a protected mode handler for processor
 exceptions.

 The exceptions it is possible to handle are:

    0x00  Divide by zero
    0x01  Debug
    0x03  Breakpoint
    0x04  Overflow
    0x05  Bounds check
    0x06  Invalid opcode
    0x07  287/387 not available
    0x08  Double fault
    0x0A  Invalid task switch segment
    0x0B  Segment not present
    0x0C  Stack fault
    0x0D  General protection fault

 Example :

    #include <stdio.h>
    #include <stdlib.h>
    #include <blx286.h>
    PEXCHAN prevhandler;
    void printstr (char *s)    /* Cannot use C screen i/o */
       {
       char c;
       while (c = *(s++))         /* Until end of string */
          {
          _asm mov ah,0eh
          _asm mov al,c
          _asm int 10h            /* Display teletype */
          }
       }
    void _interrupt far gphandler(EXCEP_FRAME ef)
       {
       char        msg [80];
       printstr ("Replacement GPF handler\n\r");
       printstr ("-----------------------\n\r");
       sprintf (msg,"Error code = %04x\n\r",ef.error_code);
       printstr (msg);
       sprintf (msg," CS:IP = %04x:%04x\n\r", ef.ret_cs, 
          ef.ret_ip);
       printstr (msg);
       DosSetExceptionHandler (0x0d,prevhandler,NULL);
       exit (255);
    }
    void main (void)
    {
    PEXCHAN        newhandler;
    newhandler = gphandler;
    if (DosSetExceptionHandler (0x0d, newhandler,&prevhandler) 
       == 0)
       {
       *((USHORT far *) 0x22222222L) = 1;     /* Cause exception */
       printf("Somehow no exception occurred\n");
       DosSetExceptionHandler (0x0d,prevhandler,NULL);
       }
    }