Q65640: ERROR ERR May Cause "Illegal Function Call" in QBX.EXE 7.00

Article: Q65640
Product(s): See article
Version(s): 7.00   | 7.00
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | SR# S900827-59 buglist7.00 fixlist7.10 | mspl13_basic
Last Modified: 20-SEP-1990

In a multiple-module program in which each of the modules contains an
active error handler, executing the statement ERROR ERR within an
error handler of any support module will normally pass control back to
the next active error handler in the CALL tree. If an active error
handler is not found, the program will terminate.

Within the QBX.EXE environment of Microsoft BASIC Professional
Development System (PDS) version 7.00, using ERROR ERR in a
module-level error handler will incorrectly generate either "Illegal
function call" or "Device I/O error". This problem does not occur when
the same program is compiled using BC.EXE.

Microsoft has confirmed this to be a problem in only the QBX.EXE
environment of BASIC PDS 7.00 for MS-DOS. This problem was corrected
in BASIC PDS version 7.10.

When the following program is run in QBX.EXE version 7.00, an "Illegal
Function Call" or "Device I/O error" results. When the program is
compiled using BC.EXE, it will compile and run without error.

MOD1.BAS
--------

   '=================This is Module 1==========================
   DECLARE SUB mod2sub1 ()        'this sub is in Mod2
   ON ERROR GOTO MainErr          'Main error Handler
   CLS
   CALL mod2sub1                  'Calls the sub in Mod2
   END
   MainErr:
      PRINT "main error "; ERR    'prints the Error number
      END

MOD2.BAS
--------

   '===================This is Module 2========================
   Mod2ErrorHandler:            'This error handler is at the
      PRINT "Mod2 Error "       'Module level in Mod2.
      ERROR ERR                 'This causes the error again.
      RESUME NEXT
   SUB mod2sub1
      ON ERROR GOTO Mod2ErrorHandler  'Goto err handler in Mod2
      ERROR 5                         'Cause an Error 5
   END SUB

Workaround for MOD2.BAS
-----------------------

To work around the problem, convert the module-level error handler (in
the MOD2.BAS support module) into a local error handler, as follows:

   SUB Mod2Sub1
        ON LOCAL ERROR GOTO Mod2ErrorHandler
        ERROR 5
        EXIT SUB
        Mod2ErrorHandler:
            PRINT "Mod2 Error "
            ERROR ERR           'Forces the error again.
            RESUME NEXT
   END SUB

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