PRB: EXTERN Attribute Prevents F4999 on Unreferenced Function

• Microsoft FORTRAN Compiler for MS-DOS, version 5.1
• Microsoft FORTRAN PowerStation for MS-DOS, versions 1.0 and 1.0a
• Microsoft FORTRAN PowerStation 32 for Windows NT, version 1.0 and 4.0

SYMPTOMS

A function that is defined using the INTERFACE TO statement and that includes the return type declaration but that is not called from within a program causes the compiler to generate this warning message:

   warning F4999: <symbol> : variable declared but not used

  warning FOR4270: unused symbol

CAUSE

The compiler is correct to report that <symbol> is not being used. This problem usually occurs when using a library of functions or subroutines. The library needs to have INTERFACE TO statements and function declarations for all routines in the library. An application may not need to call every function contained in the library. Any functions that are defined but not called result in the warning.

RESOLUTION

When declaring a function, use the EXTERN attribute as in the following code sample.

Sample Code

/* Compile options needed: none
*/

      INTERFACE TO INTEGER*4 FUNCTION Func(I)
      INTEGER*4 I [VALUE]
      END

      INTEGER*4 Func [EXTERN]

      PRINT *, 'Hello'
      END

      INTEGER*4 FUNCTION Func(I)
      INTEGER*4 I [VALUE]
          Func = I + 7
      END

STATUS

This behavior is by design.