Controlling out of bound in static arrays

By default, when an index is lower than 1 or greater than the static array length, fglrun raises error -1326, and this error is not trappable.

Note: When using a dynamic array, new elements are automatically allocated, if the index is greater than the actual array size. The error -1326 will only occur when the index is lower than 1.

Raising an index out of bounds error is normal. However, in some situations, code must execute without error and evaluate expressions using indexes that are greater than the size of the array, especially with boolean expressions in IF statements:

IF index <= max_index AND arr[index].name IS NOT NULL THEN
   ...
END IF

In this example, by default (when not using the OPTIONS SHORT CIRCUIT instruction), all parts of a boolean expression need to be evaluated, and the runtime system must get the value of the arr[index] element.

If such kind of code cannot be changed and must execute, use the fglrun.arrayIgnoreRangeError FGLPROFILE entry, to control the behavior of the runtime system when an array index is out of bounds:

fglrun.arrayIgnoreRangeError = true

When this FGLPROFILE entry is set to true, the runtime system will return the first element of the array if the index is out of bounds, and continues with the normal program flow.

Unless existing code is relying on the relaxed behavior, it is better to keep the default settings and get array out of bounds errors when the array index is invalid.

Change the code as follows, to detatch the index checking from its usage:

IF index <= max_index THEN
    IF arr[index].name IS NOT NULL THEN
       ...
    END IF
END IF

Or, use the

OPTIONS SHORT
CIRCUIT

compiler directive, to control boolean expression evaluation. You can then put both conditions in the same IF statement. When the first condition is false, the second condition is not evaluated:

OPTIONS SHORT CIRCUIT
...
IF index <= max_index AND arr[index].name IS NOT NULL THEN
   ...
END IF