The Sequel

1. If a function is intended for use by everyone, use a "normal" account to check it out.
2. Do not assume anything to be true about input data unless it is verified to be true. Expect the unexpected! A buffer overrun happens when someone, either maliciously or unintentionally, sends an application a larger chunk of data than it can handle.
3. Check where possible that you are running in the expected environment if there may be dependencies on operating system or software versions, rather than "failing silently".
4. Initialize variables before you use them.
5. If a character string in REXX is all numeric, then the NUMERIC DIGITS setting (default is 9) comes into effect for compares. This means that only the first nine digits will be checked if all characters are numeric. A simple workaround is to add a alphabetic character to each string.
6. PL/I compilers will use an implicit definition for an undeclared variable. This can be helpful when it is desired and the implications are understood. The compiler will generate an information message. Unintended use of implicitly-declared variables can be a result of misspelled variable or function names.
7. The C compiler can give very bad performance for record I/O when "noseek" has NOT been specified on fopen. The impact can be increased when RECFM=U and output is to tape.
8. The perror routine should be used after failed calls to C routines such as fopen to provide additional information on what went wrong.
9. FTP transfers from tape with spanned records or where RDWs were requested for variable-length records may not work as expected unless the appropriate READTAPEFORMAT option is specified.
10. Turn off diagnostic or tuning aids such as Language Environment storage utilization reports for production runs to avoid unnecessary overhead.

For More Information

You can find a general discussion of interface design bugs at the AskTog Bug House.

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