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@c Copyright (C) 1996, 1997, 1999, 2000, 2002, 2004, 2007 John W. Eaton
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@c This file is part of Octave.
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@c Octave is free software; you can redistribute it and/or modify it
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@c under the terms of the GNU General Public License as published by the
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@c Free Software Foundation; either version 3 of the License, or (at
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@c your option) any later version.
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@c Octave is distributed in the hope that it will be useful, but WITHOUT
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@c ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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@c FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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@c You should have received a copy of the GNU General Public License
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@c along with Octave; see the file COPYING. If not, see
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@c <http://www.gnu.org/licenses/>.
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@c The text of this file appears in the file BUGS in the Octave
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@c distribution, as well as in the Octave manual.
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@appendix Known Causes of Trouble
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This file documents known bugs in Octave and describes where and how to
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report any bugs that you may find.
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Copyright (C) 1996, 1997, 2007 John W. Eaton. You may copy, distribute, and
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modify it freely as long as you preserve this copyright notice and
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@chapter Known Causes of Trouble with Octave
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@cindex installation trouble
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@cindex known causes of trouble
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@cindex troubleshooting
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This section describes known problems that affect users of Octave. Most
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of these are not Octave bugs per se---if they were, we would fix them.
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But the result for a user may be like the result of a bug.
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Some of these problems are due to bugs in other software, some are
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missing features that are too much work to add, and some are places
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where people's opinions differ as to what is best.
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* Actual Bugs:: Bugs we will fix later.
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@appendixsec Actual Bugs We Haven't Fixed Yet
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Output that comes directly from Fortran functions is not sent through
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the pager and may appear out of sequence with other output that is sent
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through the pager. One way to avoid this is to force pending output to
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be flushed before calling a function that will produce output from
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within Fortran functions. To do this, use the command
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Another possible workaround is to use the command
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page_screen_output = "false"
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to turn the pager off.
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A list of ideas for future enhancements is distributed with Octave. See
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the file @file{PROJECTS} in the top level directory in the source
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@appendixsec Reporting Bugs
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@cindex reporting bugs
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Your bug reports play an essential role in making Octave reliable.
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When you encounter a problem, the first thing to do is to see if it is
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already known. @xref{Trouble}. If it isn't known, then you should
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Reporting a bug may help you by bringing a solution to your problem, or
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it may not. In any case, the principal function of a bug report is
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to help the entire community by making the next version of Octave work
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better. Bug reports are your contribution to the maintenance of Octave.
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In order for a bug report to serve its purpose, you must include the
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information that makes it possible to fix the bug.
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If you have Octave working at all, the easiest way to prepare a complete
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bug report is to use the Octave function @code{bug_report}. When you
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execute this function, Octave will prompt you for a subject and then
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invoke the editor on a file that already contains all the configuration
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information. When you exit the editor, Octave will mail the bug report
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@DOCSTRING(bug_report)
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* Where: Bug Lists. Where to send your bug report.
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* Reporting: Bug Reporting. How to report a bug effectively.
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* Patches: Sending Patches. How to send a patch for Octave.
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@appendixsec Have You Found a Bug?
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If you are not sure whether you have found a bug, here are some guidelines:
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If Octave gets a fatal signal, for any input whatever, that is
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a bug. Reliable interpreters never crash.
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@cindex incorrect output
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@cindex incorrect results
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@cindex results, incorrect
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@cindex answers, incorrect
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@cindex erroneous results
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@cindex wrong answers
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If Octave produces incorrect results, for any input whatever,
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@cindex undefined behavior
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@cindex undefined function value
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Some output may appear to be incorrect when it is in fact due to a
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program whose behavior is undefined, which happened by chance to give
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the desired results on another system. For example, the range operator
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may produce different results because of differences in the way floating
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point arithmetic is handled on various systems.
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@cindex erroneous messages
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@cindex incorrect error messages
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@cindex error messages, incorrect
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If Octave produces an error message for valid input, that is a bug.
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@cindex invalid input
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If Octave does not produce an error message for invalid input, that is
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a bug. However, you should note that your idea of ``invalid input''
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might be my idea of ``an extension'' or ``support for traditional
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@cindex improving Octave
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If you are an experienced user of programs like Octave, your suggestions
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for improvement are welcome in any case.
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@appendixsec Where to Report Bugs
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@cindex bug report mailing lists
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@cindex reporting bugs
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@cindex bugs, reporting
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If you have Octave working at all, the easiest way to prepare a complete
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bug report is to use the Octave function @code{bug_report}. When you
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execute this function, Octave will prompt you for a subject and then
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invoke the editor on a file that already contains all the configuration
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information. When you exit the editor, Octave will mail the bug report
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If for some reason you cannot use Octave's @code{bug_report} function,
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send bug reports for Octave to @email{bug@@octave.org}.
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@strong{Do not send bug reports to @samp{help-octave}}. Most users of
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Octave do not want to receive bug reports. Those that do have asked to
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be on the mailing list.
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As a last resort, send bug reports on paper to:
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Octave Bugs c/o John W. Eaton
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University of Wisconsin-Madison
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Department of Chemical Engineering
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1415 Engineering Drive
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Madison, Wisconsin 53706 USA
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@appendixsec How to Report Bugs
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@cindex bugs, reporting
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Send bug reports for Octave to one of the addresses listed in
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The fundamental principle of reporting bugs usefully is this:
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@strong{report all the facts}. If you are not sure whether to state a
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fact or leave it out, state it!
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Often people omit facts because they think they know what causes the
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problem and they conclude that some details don't matter. Thus, you might
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assume that the name of the variable you use in an example does not matter.
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Well, probably it doesn't, but one cannot be sure. Perhaps the bug is a
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stray memory reference which happens to fetch from the location where that
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name is stored in memory; perhaps, if the name were different, the contents
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of that location would fool the interpreter into doing the right thing
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despite the bug. Play it safe and give a specific, complete example.
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Keep in mind that the purpose of a bug report is to enable someone to
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fix the bug if it is not known. Always write your bug reports on
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the assumption that the bug is not known.
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Sometimes people give a few sketchy facts and ask, ``Does this ring a
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bell?'' This cannot help us fix a bug. It is better to send a complete
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bug report to begin with.
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Try to make your bug report self-contained. If we have to ask you for
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more information, it is best if you include all the previous information
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in your response, as well as the information that was missing.
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To enable someone to investigate the bug, you should include all these
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The version of Octave. You can get this by noting the version number
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that is printed when Octave starts, or running it with the @samp{-v}
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A complete input file that will reproduce the bug.
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A single statement may not be enough of an example---the bug might
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depend on other details that are missing from the single statement where
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the error finally occurs.
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The command arguments you gave Octave to execute that example
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and observe the bug. To guarantee you won't omit something important,
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list all the options.
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If we were to try to guess the arguments, we would probably guess wrong
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and then we would not encounter the bug.
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The type of machine you are using, and the operating system name and
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The command-line arguments you gave to the @code{configure} command when
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you installed the interpreter.
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A complete list of any modifications you have made to the interpreter
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Be precise about these changes---show a context diff for them.
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Details of any other deviations from the standard procedure for installing
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@cindex incorrect output
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@cindex incorrect results
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@cindex results, incorrect
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@cindex answers, incorrect
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@cindex erroneous results
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@cindex wrong answers
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A description of what behavior you observe that you believe is
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incorrect. For example, "The interpreter gets a fatal signal," or, "The
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output produced at line 208 is incorrect."
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Of course, if the bug is that the interpreter gets a fatal signal, then
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one can't miss it. But if the bug is incorrect output, we might not
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notice unless it is glaringly wrong.
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Even if the problem you experience is a fatal signal, you should still
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say so explicitly. Suppose something strange is going on, such as, your
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copy of the interpreter is out of synch, or you have encountered a bug
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in the C library on your system. Your copy might crash and the copy
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here would not. If you said to expect a crash, then when the
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interpreter here fails to crash, we would know that the bug was not
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happening. If you don't say to expect a crash, then we would not know
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whether the bug was happening. We would not be able to draw any
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conclusion from our observations.
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Often the observed symptom is incorrect output when your program is run.
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Unfortunately, this is not enough information unless the program is
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short and simple. It is very helpful if you can include an explanation
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of the expected output, and why the actual output is incorrect.
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If you wish to suggest changes to the Octave source, send them as
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context diffs. If you even discuss something in the Octave source,
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refer to it by context, not by line number, because the line numbers in
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the development sources probably won't match those in your sources.
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Here are some things that are not necessary:
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@cindex bugs, investigating
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A description of the envelope of the bug.
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Often people who encounter a bug spend a lot of time investigating which
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changes to the input file will make the bug go away and which changes
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will not affect it. Such information is usually not necessary to enable
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us to fix bugs in Octave, but if you can find a simpler example to
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report @emph{instead} of the original one, that is a convenience.
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Errors in the output will be easier to spot, running under the debugger
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will take less time, etc. Most Octave bugs involve just one function, so
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the most straightforward way to simplify an example is to delete all the
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function definitions except the one in which the bug occurs.
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However, simplification is not vital; if you don't want to do
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this, report the bug anyway and send the entire test case you
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A patch for the bug. Patches can be helpful, but if you find a bug, you
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should report it, even if you cannot send a fix for the problem.
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@node Sending Patches
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@appendixsec Sending Patches for Octave
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@cindex improving Octave
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@cindex diffs, submitting
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@cindex patches, submitting
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@cindex submitting diffs
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@cindex submitting patches
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If you would like to write bug fixes or improvements for Octave, that is
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very helpful. When you send your changes, please follow these
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guidelines to avoid causing extra work for us in studying the patches.
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If you don't follow these guidelines, your information might still be
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useful, but using it will take extra work. Maintaining Octave is a lot
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of work in the best of circumstances, and we can't keep up unless you do
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Send an explanation with your changes of what problem they fix or what
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improvement they bring about. For a bug fix, just include a copy of the
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bug report, and explain why the change fixes the bug.
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Always include a proper bug report for the problem you think you have
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fixed. We need to convince ourselves that the change is right before
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installing it. Even if it is right, we might have trouble judging it if
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we don't have a way to reproduce the problem.
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Include all the comments that are appropriate to help people reading the
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source in the future understand why this change was needed.
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Don't mix together changes made for different reasons.
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Send them @emph{individually}.
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If you make two changes for separate reasons, then we might not want to
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install them both. We might want to install just one.
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Use @samp{diff -c} to make your diffs. Diffs without context are hard
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for us to install reliably. More than that, they make it hard for us to
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study the diffs to decide whether we want to install them. Unidiff
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format is better than contextless diffs, but not as easy to read as
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If you have GNU diff, use @samp{diff -cp}, which shows the name of the
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function that each change occurs in.
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Write the change log entries for your changes.
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Read the @file{ChangeLog} file to see what sorts of information to put
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in, and to learn the style that we use. The purpose of the change log
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is to show people where to find what was changed. So you need to be
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specific about what functions you changed; in large functions, it's
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often helpful to indicate where within the function the change was made.
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On the other hand, once you have shown people where to find the change,
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you need not explain its purpose. Thus, if you add a new function, all
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you need to say about it is that it is new. If you feel that the
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purpose needs explaining, it probably does---but the explanation will be
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much more useful if you put it in comments in the code.
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If you would like your name to appear in the header line for who made
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the change, send us the header line.
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@appendixsec How To Get Help with Octave
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@cindex help, where to find
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The mailing list @email{help@@octave.org} exists for the discussion of
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matters related to using and installing Octave. If would like to join
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the discussion, please send a short note to
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@email{help@strong{-request}@@octave.org}.
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@strong{Please do not} send requests to be added or removed from the
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mailing list, or other administrative trivia to the list itself.
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If you think you have found a bug in the installation procedure,
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however, you should send a complete bug report for the problem to
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@email{bug@@octave.org}. @xref{Bug Reporting}, for
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information that will help you to submit a useful report.
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