DOCERR: Code in Manual Incorrect: COMMON and EQUIVALENCE

• Microsoft FORTRAN for MS-DOS, versions 5.0 and 5.1
• Microsoft FORTRAN for OS/2, versions 5.0 and 5.1

SYMPTOMS

When compiled with Microsoft FORTRAN version 5.0 or 5.1 under MS-DOS or OS/2, the sample program given on page 132 of the "Microsoft FORTRAN Advanced Topics" version 5.0 manual and page 105 of the "Microsoft FORTRAN Advanced Topics" version 5.1 manual generates the following error:

   error F2318: A, B : EQUIVALENCE: in different common blocks

CAUSE

The version 5.1 FORTRAN "Reference Manual" states:

   An EQUIVALENCE statement cannot share memory between two different
   common blocks or between elements of the same common block.

RESOLUTION

To avoid this error, compile the code after removing either A or B or both the arrays from COMMON blocks.

MORE INFORMATION

The following code, which is incorrect, is from the "Microsoft FORTRAN Advanced Topics" manual:

      integer a(10,20), b(20,30)
      common /cba/a, /cbb/b
      equivalence (a(10,20), b(1,1))
      end

      integer a(10,20), b(20,30)
      common /cba/ a
      equivalence (a(10,20), b(1,1))
      end