P4016

Code

P4016

Message

Function declaration name is duplicated

This error occurs when a function declaration name is duplicated within the same scope.

Example

The following code will generate error P4016:

FUNCTION MyFunction : INT
    MyFunction := 0;
END_FUNCTION

FUNCTION MyFunction : INT  (* Error: Duplicate function name *)
    MyFunction := 0;
END_FUNCTION

PROGRAM main
    VAR
        dummy : INT;
    END_VAR
END_PROGRAM

The function MyFunction is declared twice, which is not allowed.

To fix this error, ensure all function names are unique within their scope:

FUNCTION MyFunction1 : INT
    MyFunction1 := 0;
END_FUNCTION

FUNCTION MyFunction2 : INT
    MyFunction2 := 0;
END_FUNCTION

PROGRAM main
    VAR
        dummy : INT;
    END_VAR
END_PROGRAM

Note that changing the return type or the parameter list of one of the duplicates does not resolve the error, because IEC 61131-3 does not permit overloading. The two declarations below still produce P4016:

FUNCTION Scale : INT
    VAR_INPUT v : INT; END_VAR
    Scale := v;
END_FUNCTION

FUNCTION Scale : REAL  (* Error: same name, different signature is still a duplicate *)
    VAR_INPUT v : REAL; END_VAR
    Scale := v;
END_FUNCTION

PROGRAM main
    VAR
        dummy : INT;
    END_VAR
END_PROGRAM

Give each function a distinct name (for example, ScaleInt and ScaleReal) instead of relying on overloading.

See Also

  • FUNCTION — FUNCTION declaration syntax

  • Functions — names reserved by the standard library

  • P4013 — POU declaration name duplicated (programs, function blocks)

  • P4014 — symbol (variable) declaration name duplicated

  • P4015 — user-defined type collides with a standard-library type

References

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