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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