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, 1.0a
• Microsoft Fortran Powerstation 32 for Windows NT, versions 1.0, 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

C  INTERFACE TO usually in .FI
      INTERFACE TO INTEGER*4 FUNCTION Func(I)
      INTEGER*4 I [VALUE]
      END

C  Declaration usually in .FD (remove [EXTERN] to get the F4999)
      INTEGER*4 Func [EXTERN]

C  Start of program
      PRINT *, 'Hello'
      END

C  Body of function possibly somewhere else
      INTEGER*4 FUNCTION Func(I)
      INTEGER*4 I [VALUE]
          Func = I + 7
      END 

STATUS

This behavior is by design.

Additional query words: 5.00 5.10 1.00 1.00a 4.00

Keywords : kbcode kbLangFortran
Version : :1.0,1.0a,4.0,5.1
Platform : MS-DOS NT WINDOWS
Issue type :