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Re: Debug output etc, cluttering the terminal

On Sun, 15 Aug 2010 08:51:21 +0200
Michael Welle <mwe012008@gmx.net> wrote:

> > It's debug output, it is useful when debugging and you need the
> > output, e.g. when fixing bugs and the user can just be asked to run
> > the command from the terminal and post the output to help in
> > debugging the bug report. Generally, the debug output for a
> > particular release tends to reflect the issues which upstream were
> > working on most intensively before that release and therefore can
> > have a direct impact on the likelihood of new bugs or regressions
> > in old bugs.
> >
> > It's not clutter. If you don't want to see it, run the command and
> > redirect stderr.
> I agree with your opinion about the usefulness of debug output. And
> -as one might guess- I disagree with your opinion about  how debug
> output should be handled. Do Debian distribute programmes to its user
> base, that are still in debug phase?

Yes and will continue to do so. All software is susceptible to bugs and
all software needs to have debug support. Mature software needs more
debug support than pre-alpha software because bugs in mature packages
tend to be corner-cases and obscure use cases, i.e. harder to identify.

Every software package is constantly being debugged. Even the kernel
produces debug output in the case of particular errors - including
messages which appear on every terminal on the machine and sound a
fixed volume beep. Depending on the circumstances, this can be
something as simple as not taking a USB networking interface down
before removing the USB cable. Depends which module is in use.

> Aren't debug switches sold
> anymore?

"sold" ??? Programs support --debug or --verbose options on the command
line for debugging of errors which are not often seen.

> One can forget to switch debug output off. That's no biggy,
> mistakes happen. But have it switched on per default is strange and
> embarassing.

Nothing of the sort. Programs that do not provide debug output should
make log files containing debug output.

When bugs are hard to reproduce, having debug output on by default is
extremely important for many mature packages.

This isn't about forgetting to switch debugging off, this is about
helping users and developers actually fix bugs.

Difficult bugs can appear as a subtle change in the debug output, even
if the program continues to operate normally (or close to normally),
only to fail later. e.g. a package can develop a bug which corrupts the
data storage format used by the package, the debug output includes a
line that a variable of type foo has been written out as type bar but
is still of type foo inside the program. Close the program, try to
reload the exported data, containing the type bar, and the program
fails. The only way to debug this is to have the debug output available
by default and then include the details of how that data was obtained
into the bug report.


Neil Williams

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