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Application Programming: Debugging and Error-Handling |
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IDL divides possible execution errors into three categories: input/output, math, and all others. There are three main error-handling routines: CATCH, ON_ERROR, and ON_IOERROR. CATCH is a generalized mechanism for handling exceptions and errors. The ON_ERROR routine handles regular errors when an error handler established by the CATCH procedure is not present. The ON_IOERROR routine allows you to change the default way in which input/output errors are handled. The FINITE and CHECK_MATH routines provide control over math errors.
You can also write code in such a manner as to anticipate and handle potential errors, especially when you are writing your own routines. See the following topics in Creating Procedures and Functions for details:
Error handlers established by calls to CATCH supersede calls to ON_ERROR. However, calls to ON_IOERROR made in the procedure that causes an I/O error supersede any error handling mechanisms created with CATCH and the program branches to the label specified by ON_IOERROR.
The following figure is a flow chart of how errors are handled in IDL.
IDL Online Help (March 06, 2007)
