Hardware Errors During CALL INTERRUPT Hang the System (26543)




This article was previously published under Q26543

SYMPTOMS

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.

STATUS

Microsoft has confirmed this to be a bug 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).

MORE INFORMATION

When you are inside the editor and using the DOS interrupt procedures (INT86OD, 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
Modification Type: Minor Last Reviewed: 1/8/2003
Keywords: KB26543
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