SA0007: Address operator on constants

Detects lines of code where the operator ADR is applied for a constant

Justification: Using a pointer to a constant variables overrides the CONSTANT property of the variable. The variable can be changed by means of the pointer without any notification from the compiler.

Exception: In rare cases, it might be useful to pass a pointer to a constant to a function. However, you need to make sure that this function does not change the transferred value. Whenever possible, use VAR_IN_OUT CONSTANT.

Importance: High

Tip

When the Replace constants option is selected in the Compiler Options of the project settings, the address operator is not permitted for scalar constants (integer, BOOL, REAL) and a compile error is issued. (Constant strings, structures, and arrays always have an address.)

Example 19. Example

PROGRAM PLC_PRG
VAR CONSTANT
        c_iValue : INT := INT#15;
END_VAR
VAR
        poiValue : POINTER TO INT;
END_VAR

poiValue := ADR(c_iValue); // SA0007

Output in the Messages view:

SA0007: Address to constant variable 'c_iValue'