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Performing external functions takes place in the same environment as running the ESL scripts that call them. If the implementation of an external function ends with a catchable C ++ exception, this exception is caught and promoted as a runtime error to the ESL. However, some C ++ errors (e. g., NULL dereference, division 0) do not generate catchable exceptions and end up with the fallout a crash of the library and the process used by using the library (Event handler), so it is important to care thoroughly of handling handle errors when implementing external functions.
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