Q39379: QB.EXE 4.50 "Binding…" then Hang If SWAP User-TYPE Strings

Article: Q39379
Product(s): See article
Version(s): 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist4.50 SR# S881206-72 | mspl13_basic
Last Modified: 24-MAR-1989

SWAPping two string variables that are fields of a user-defined type
can display the "Binding..." message and then hang the QuickBASIC
QB.EXE Version 4.50 editor. Hanging does not happen SWAPping
non-user-defined type strings or other types of variables. The hanging
does not occur in programs compiled with BC.EXE Version 4.50, it is
just a QB.EXE editor problem.

Microsoft has confirmed this to be a problem in Version 4.50. We are
researching this problem and will post new information as it becomes
available.

QB.EXE Versions 4.00 and 4.00b do not have this problem.

Putting the TYPE variables in either $DYNAMIC or $STATIC arrays still
hangs. If an INTEGER or DOUBLE appears in the record before the string
field that is being swapped, then you can usually warm reboot,
otherwise it usually requires a cold reboot. Other variables such as
floating point or other TYPES do not prevent the cold reboot. Which
String is swapped (1-5) in the following record makes no difference.

Swapping any non-string type of field in a user-defined record does
not hang the computer. Swapping both variable- and fixed-length
strings as single variables (not in record) also does not hang the
computer.

The following code demonstrates the problem:

   TYPE rectype
      num1 AS INTEGER
      string1 AS STRING * 16
      string2 AS STRING * 16
      string3 AS STRING * 16
      string4 AS STRING * 16
      string5 AS STRING * 16
   END TYPE
   DIM var1  AS rectype, var2 AS rectype
   var1.string1 = "String1"
   var2.string1 = "String2"
   SWAP var1.string1, var2.string1
   ' The QB.EXE environment will freeze up at this SWAP statement.

To work around the problem, use a standard swapping technique with two
variables and a temporary variable:

   DIM var1 as rectype, var2 as rectype, temp as rectype
   temp.string1 = var1.string1      ' 1. a -> temp
   var1.string1 = var2.string1      ' 2. b -> a
   var2.string1 = temp.string1      ' 3. temp -> b

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