SA0072: Invalid uses of counter variable

Function	Determines write access operations to a counter variable within a FOR loop.
Reason	Manipulating the counter variable in a FOR loop can easily lead to an infinite loop. To prevent the execution of the loop for certain values of the counter variables, use CONTINUE or simply IF.
Importance	High
PLCopen rule	L12

Sample:

PROGRAM MAIN
VAR_TEMP
    nIndex  : INT;
END_VAR
VAR
    aSample : ARRAY[1..10] OF INT;
    nLocal  : INT;
END_VAR

FOR nIndex := 1 TO 10 BY 1 DO
    aSample[nIndex] := nIndex;                      // no error
    nLocal          := nIndex;                      // no error
 
    nIndex          := nIndex - 1;                  // => SA0072
    nIndex          := nIndex + 1;                  // => SA0072
    nIndex          := nLocal;                      // => SA0072
END_FOR