EMBOSS: C2 Error Messages

EMBOSS can write messages at the following levels: FATAL, ERROR, WARN, INFO. Currently FATAL writes to standard error and abort the application while the others write to standard error and continue. These could be divided in various ways, but all error calls have to follow any agreed convention.

Issues:

1. Error messages are simple text with "ERROR:" etc. to indicate the level. Further information could be added automatically (source file, line number, error numbers to use a central error message list, etc.)
2. Line numbers and source files are provided by a macro for coding errors.
3. Error messages should be parsed by scripts when an application fails, so they need a standard format that can be recognised. Work on this is still in progress.
4. Error messages could be duplicated in files, and written using an error code. SRS does this, but EMBOSS still uses text in the source code.
5. Numbered messages can be checked by an output parser against expected error codes. The number should appear in the message, and should be used as the abort code if the program terminates. Again, this is not yet implemented.
6. Unnumbered messages should also be available, with a general default code to replace the number.
7. Standard error messages (out of memory, bad sequence format) could be set by codes to standardise them where they may be generated in more than one source code line. At present, these depend on a single call to write the error message.