Microsoft KB Archive/42662

From BetaArchive Wiki
Knowledge Base


Corrupt Parameters in SUB Using PRINT with Comma; BC.EXE 4.50

Article ID: 42662

Article Last Modified on 11/21/2006

This article was previously published under Q42662

SYMPTOMS

In the example below, parameters that are passed to a SUBprogram and printed out with a comma separating them will be corrupted within the SUBprogram. This problem occurs only when the program has been compiled to an EXE file. Altering the compile switches does not change the incorrect results.

The program below demonstrates this problem. The problem exists only when the parameters have been passed to a SUBprogram and are compiled to an EXE file.

This problem occurs in .EXE programs only in QuickBasic version 4.50. Microsoft is researching this problem and will post new information here as it becomes available. Previous versions of QuickBasic, and Microsoft Basic Compiler versions 6.00, 6.00b, and 7.00, produce the correct results (fixlist6.00 fixlist6.00b fixlist7.00).

The following program is TEST.BAS, which creates two variables and passes them to a subroutine. The subroutine then prints the variables.

   DECLARE SUB test (a, b)
   a = 1
   b = 2
   CALL test(a, b)
   PRINT a, b

   SUB test (a, b)
      PRINT a, b
      b = 100
      PRINT a, b   ' This prints incorrectly.
      b = 256
   END SUB
                

The compiled EXE file prints the following incorrect output:

   1             2
   1             3.363116E-44
   1             100
                

If any PRINT statement is altered (for example, the first "PRINT a, b" in the SUB is changed to a "PRINT a; b"), or if the program is run from the QB.EXE environment, the correct output will be produced, as follows:

   1             2
   1             100
   1             256
                

Another workaround for the problem is to compile with BC /X, or to add "ON ERROR GOTO label" and "RESUME" statements to the program.

Another workaround is to assign a local variable to the passed variable and then print the local variable instead of the passed variable, for example:

   SUB test (a, b)
      x = a  ' Assign passed parameter to local variable.
      y = b  ' Assign passed parameter to local variable.
      PRINT x, y
      y = 100
      PRINT x, y   ' This prints correctly.
      y = 256
      a = x  ' Pass back values to parameters
      b = y  ' Pass back values to parameters
   END SUB
                


Additional query words: QuickBas SR# S890309-98 buglist4.50

Keywords: KB42662