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Q26543: Hardware Errors During CALL INTERRUPT Hang the System

Article: Q26543
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom buglist4.00 buglist4.00b buglist4.50 | mspl13_basic
Last Modified: 31-JAN-1990

DOS interrupt calls that result in a hardware error, such as an open
disk-drive door or a bad sector, cause the system to hang.

Microsoft has confirmed this to be a problem in QuickBASIC Versions
4.00, 4.00b, and 4.50, and in Microsoft BASIC Compiler Versions 6.00
and 6.00b (buglist6.00, buglist6.00b) for MS-DOS and MS OS/2. This
problem was corrected in Microsoft BASIC Professional Development
System (PDS) Version 7.00 for MS-DOS and MS OS/2 (fixlist7.00).

When you are inside the editor and using the DOS interrupt procedures
(INT86OLD, INTERRUPT) to open a data file that is on a floppy disk, if
the disk-drive door is left open, the error is caught and handled by
the editor. However, if the program is made into an executable, when
the door is left open, the error is not trapped and control is never
returned to the BASIC program. This effectively hangs the system.

To work around the problem, OPEN a file for input on the floppy disk
and trap potential disk errors with ON ERROR GOTO before attempting to
CALL INTERRUPT.

Results of testing with earlier versions show that the errors are
trapped correctly with QuickBASIC Version 3.00; therefore, the problem
does not occur in Version 3.00.

The following is example code:

TYPE RegType
     ax    AS INTEGER
     bx    AS INTEGER
     cx    AS INTEGER
     dx    AS INTEGER
     bp    AS INTEGER
     si    AS INTEGER
     di    AS INTEGER
     flags AS INTEGER
END TYPE

DECLARE SUB INTERRUPT (intnum AS INTEGER, inreg AS RegType, outreg AS RegType

DIM inarray AS RegType, outarray AS RegType

file$ = "a:dummy.dat" + CHR$(0)

inarray.ax = &H3D02
inarray.dx = SADD(file$)

CALL INTERRUPT(&H21, inarray, outarray)
PRINT outarray.flags
PRINT outarray.ax
END

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