POINTER TO is type-unsafe

Variables defined as a POINTER TO data-type are considered type-unsafe in the sense that assigning between incompatible types will not be caught. For example the following code, while incorrect, will not return any diagnostics when compiling:

VAR
    stringVar : STRING;
    unsafePtrA : POINTER TO DINT := ADR(stringVar);
    unsafePtrB : POINTER TO DINT := REF(stringVar);
END_VAR

Note that for class and function block hierarchies, POINTER TO assignments are validated — the compiler checks that the pointee types are related via EXTENDS (see E125). POINTER TO is the recommended mechanism for polymorphism per IEC 61131-3.

For other types, consider using REF_TO instead of POINTER TO, which is a type-safe alternative and should catch type-mismatches early on.