P2027

Code

P2027

Message

Array index out of bounds

This error occurs when an array subscript is a constant outside the indexes the array declares.

Each dimension of an array declares the indexes of its elements. ARRAY[1..5] OF INT has elements 1 through 5, so a subscript of 6 names an element the array does not have.

Example

The following code will generate error P2027:

Try it

Source

PROGRAM main
    VAR
        readings : ARRAY[1..5] OF INT;
    END_VAR

    readings[6] := 10;  (* Error: readings has elements 1 to 5 *)
END_PROGRAM

To fix this error, use an index the array declares:

Try it

Source

PROGRAM main
    VAR
        readings : ARRAY[1..5] OF INT;
    END_VAR

    readings[5] := 10;
END_PROGRAM

Or declare the array with room for the index:

Try it

Source

PROGRAM main
    VAR
        readings : ARRAY[1..6] OF INT;
    END_VAR

    readings[6] := 10;
END_PROGRAM

Where the check applies

Each subscript of a multi-dimensional array is checked against its own dimension:

Try it

Source

PROGRAM main
    VAR
        grid : ARRAY[1..3, 0..2] OF INT;
    END_VAR

    grid[1, 3] := 0;  (* Error: the second dimension is 0 to 2 *)
END_PROGRAM

A constant expression is checked by its value, so readings[3 + 3] is reported the same way as readings[6]. A subscript that is worked out while the program runs, or that names a constant, is checked when the program runs instead: an index outside the array stops the program with V4005.

See Also

• P2024 — an array dimension whose range is invalid

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