Declaring UDFs with FREE IT

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InterBase FREE_IT keyword allows InterBase users to write thread-safe UDF functions without memory leaks.

Whenever a UDF returns a value by reference to dynamically allocated memory, you must declare it using the FREE_IT keyword in order to free the allocated memory.

Note:
You must not use FREE_IT with UDFs that return a pointer to static data, as in the “multi-process version” example on page Thread-safe UDFs.

The following code shows how to use this keyword:

DECLARE EXTERNAL FUNCTION lowers VARCHAR(256)
RETURNS CSTRING(256) FREE_IT
ENTRY POINT 'fn_lower' MODULE_NAME 'ib_udf'

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