Compiler Warning C0517

Message: Should not access internal object <object name> of library <library name>

Possible error cause: A library contains a POU, whose visibility is restricted to this library with the INTERNAL keyword. The POU in a SIZEOF operator is used from outside of this library.

Error correction: Change the visibility of the POU (for example, remove the INTERNAL keyword) or change the declaration of the variable.

PROGRAM PLC_PRG
VAR
    somevar1 : INT := SIZEOF(MyLib.POU);
END_VAR