Commonly used debugging tools
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There are some relatively simple but commonly used debugging tools that might answer questions of for example why your installation of FlightGear will not run properly or at all, why an aircraft might have problems or why flying in a certain area always cause FlightGear crashes.
The more useful of those tool are the console window (also known as the "black box" or confusingly the "command line"), the
fgfs.log file and the property browser.
There are of course times when these will not do, and sometimes one would have to compile FlightGear from source and add some additional debugging features to find some bugs.
Debug level setting
Before we go any further we should mention the debug level setting (also known as log level). When FlightGear runs it will output information on various things. As a default only things that are expected to cause troubles are output, but by setting a higher debug level more information will be shown. At the highest debug level one can expect FlightGear to run slow due to all the debug output.
There are five debug levels:
- Will output very frequent messages. Using this setting might slow down FlightGear a lot, but might show problems not otherwise found.
- Will output less frequent debug messages.
- Will output informatory messages.
- Will output messages about possibly impeding problems.
- Will output messages about very possibly impeding problems. This is the default level.
Setting the debug level
In FGRun go to the last page click Advanced... then, in the list to the left, click "Debug" and then chose the desired debug level in the list.
| Note Debug levels must be lowercase. For example |
--log-level=debug level to your command line.
The console window
Before FlightGear 2.6 this was always opened in a separate window when starting FlightGear through the FGRun wizard, but these days it is normally hidden and can be shown by ticking a checkbox, "Show command line".
The startup log file contains nearly the same information that is output on the console.
The goal of adding the log file was to capture some debugging output in a way that is robust for users, i.e just works, and works ‘historically’, i.e is useful when a problem occurs since it was already enabled. The level is fixed at INFO because a lower level wouldn’t contain enough detail for debugging, but a higher level (SG_DEBUG) the files would be huge for a long FG session. This is my decision of course and it can be changed if people are happy with 100MB+ text files in their FG_HOME. Or we add a new option to set the file-log-level, but again the intention was for this feature to be as automatic as possible.
The property browser
See Property browser for the main article about this subject.
The property browser is a tool useful for many purposes. It might for example tell if a property is tied and can not be written to.