Variable with Periods in COMMON Block Can Cause Problems (42586)

SYMPTOMS

In the Microsoft QB.EXE editor, CHAINing between programs that have a COMMON block can cause errors, under the following conditions:

The programs have a COMMON block.
The COMMON block contains an array, a user-defined TYPE variable, and a simple variable that contains one or more periods.

The result is an "array not defined" error message in the CHAINed-to program. If the period(s) are removed from the simple variable, the programs CHAIN and run correctly. This error occurs only when running in the QB.EXE editor. The programs execute properly after being compiled with BC.EXE.

STATUS

Microsoft has confirmed this to be a bug in QuickBasic Versions 4.00, 4.00b, and 4.50. This problem was corrected in Microsoft Basic Professional Development System (PDS) Version 7.00 (fixlist7.00). Microsoft also recommends that you do not use periods in variable names, since the period is now used to distinguish between user-defined-TYPE variables. There may be conflicts between the two usages.

MORE INFORMATION

In the following program examples, the COMMON block consists of an integer array, a user-defined-TYPE variable, and a single-precision variable. If PROG1.BAS is run inside the QuickBasic environment, a "Subscript out of range" error occurs in PROG2.BAS, on the PRINT statement. This is because the array dimensions have not been correctly passed in the COMMON block.

If the periods are removed from the variable x.to.y in PROG2.BAS, the program executes normally. Also, if the programs are compiled as they appear here with BC.EXE, they CHAIN together and run properly.

Code Example

'----------------------------------- PROG1.BAS
'$DYNAMIC
TYPE test
  a AS INTEGER
  b AS INTEGER
END TYPE
COMMON SHARED c() AS INTEGER
COMMON SHARED Typed AS test
COMMON SHARED x.to.y
DIM SHARED c(1 TO 60) AS INTEGER

c(3) = 42
PRINT "Press a key to CHAIN to PROG2..."
WHILE INKEY$ = "": WEND
CHAIN "PROG2"
END


'----------------------------------- PROG2.BAS
'$DYNAMIC
TYPE test
  a AS INTEGER
  b AS INTEGER
END TYPE
COMMON SHARED c() AS INTEGER
COMMON SHARED Typed AS test
COMMON SHARED x.to.y

PRINT UBOUND(c), c(3)
END