BUG: Access Violation or R6018 Executing IF Statement

• Microsoft FORTRAN PowerStation for MS-DOS, version 1.0a
• Microsoft FORTRAN PowerStation 32 for Windows NT, version 1.0

SYMPTOMS

For FORTRAN PowerStation 32, an access violation occurs and for FORTRAN PowerStation, runtime error R6018 and an unexpected heap error occur when you execute code where:

• There is an IF statement alone (not "IF... THEN...").

• There is a call to a subroutine that takes a character argument in the IF block.
• The actual argument passed to the subroutine is a character expression that includes concatenation of characters.
• The IF expression is evaluated as ".FALSE" so that the call is not carried out.

RESOLUTION

Use one of the following to work around the problem:

• Use a block IF (that is, "IF... THEN ...") rather than an IF statement alone.

  -or-

• Assign the character expression to a temporary variable instead of passing it directly to the subroutine.

STATUS

Microsoft has confirmed this to be a bug in Microsoft FORTRAN PowerStation, version 1.0a for MS-DOS and version 1.0 for Windows NT. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

To reproduce the problem, compile and run the following sample code:

Sample Code

C compile options needed: none

         CHARACTER*80 A
         CHARACTER*3 end
         LOGICAL L
         end  = 'End'
         L = .FALSE.
   C1      L = .TRUE.
         A = 'This format bombs...'//end
   C2      IF (L)  print *, A
         IF (L)  print *, 'This format bombs...'//end
   C3      IF (L) then
   C3        print *, 'This format bombs...'//end
   C3      end if
         print *, end
         END

• Uncomment C1.

  -or-

• Comment out the single line "IF" and uncomment C2.

  -or-

• Comment out the single line "IF" and uncomment C3.