SG LOG: Difference between revisions

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(the talk page contained lots of useful info)
 
(Minor changes; +related: Commonly used debugging tools#Console and startup log output)
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<code>SG_LOG</code> is a wrapper macro for the [[SimGear]] <code>logstream</code> class.  By default, the <code>logstream</code> class writes all output to the [[console]].  <code>SG_LOG</code> simplifies debugging for core developers who regularly [[Building FlightGear|compile from source]].  It allows you to easily associate your debug messages with a "channel" and with a "priority". This mechanism allows users to explicitly enable to certain log messages, while ignoring others. This can be helpful in order to troubleshoot certain problems.


SG_LOG is just a wrapper macro for the SimGear "logstream" class (all output being by default written to the console!). If you are interested in simply logging certain properties to a file at runtime, you may want to use another mechanism - which is more flexible and doesn't require recompilation (see below for more details).
== Usage ==
Logging settings can be modified using the <code>--log-level=[level]</code> and <code>--log-class=[class]</code> [[command line]] options. Where <code>level</code> is one of the following:
* <code>bulk</code>
* <code>debug</code>
* <code>info</code>
* <code>warn</code>
* <code>alert</code>
* <code>popup</code>
And <code>class</code> is a white space seperated list of any (combination) of the following:
* <code>all</code>
* <code>ai</code>
* <code>enviroment</code>
* <code>flight</code>
* etc.


So, the SG_LOG macro just simplifies usage, and is purely meant to be used by programmers/developers, who regularly recompile the source code.
For a complete list of available classes, see {{simgear file|simgear/debug/debug_types.h}}.
If you just want to log some runtime data to a file, there are several other more flexible ways to do this (possible via networking/scripting or XML).


Basically, the macro allows you to easily associate your debug messages with a "channel" and a "priority".
If you are interested in simply logging certain properties to a file at runtime, you can use either FlightGear's built-in [[Logging properties|logging framework]], or the [[generic protocol]].


Which means that you can further specify each log message with a channel (think like a "parent" subsystem, to which the message belongs) and also a priority to indicate if it's a critical/non-critical message.
== Related content ==
=== Wiki articles ===
* [[Command line options#Debugging Options]]
* [[Commonly used debugging tools#Console and startup log output]]


This mechanism allows users to explicitly enable/subscribe to certain log messages, only - while ignoring others. This can be helpful in order to troubleshoot certain problems.
=== Source code ===
* {{simgear file|simgear/debug/logstream.cxx}}
* {{simgear file|simgear/debug/logstream.hxx}}
* {{simgear file|simgear/debug/debug_types.h}}


Logging settings can be modified using the --log-level command line option, detailed help about most available command line options can be obtained from the fgfs executable by calling it with the following arguments: "--help --verbose".
[[Category:Core developer documentation]]
 
All necessary details can be obtained from the source code (SG & FG) and its documentation/comments:
* http://www.simgear.org/doxygen/structlogstream__base.html
* http://simgear.org/doxygen/logstream_8hxx.html
* http://simgear.org/doxygen/logstream_8hxx-source.html
* http://www.simgear.org/doxygen/classlogstream.html
* http://www.simgear.org/doxygen/structloglevel.html
* http://www.simgear.org/doxygen/classlogbuf.html
 
So, you just pass a channel and a logging priority/class to the macro, available log channels and priorities can be found here:
* http://simgear.org/doxygen/debug__types_8h.html
* http://simgear.org/doxygen/debug__types_8h-source.html
* http://cvs.flightgear.org/simgear/doxygen/debug__types_8h-source.html
 
For logging only certain data/properties to a file, you may want to use another logging facility:
* http://cvs.flightgear.org/viewvc/source/src/Main/logger.cxx?revision=1.7&view=markup
 
 
You can also add your own, custom, log level to SimGear, see $SG_SRC/debug/debug_types.h: http://docs.freeflightsim.org/simgear/debug__types_8h.html

Revision as of 08:33, 27 September 2020

SG_LOG is a wrapper macro for the SimGear logstream class. By default, the logstream class writes all output to the console. SG_LOG simplifies debugging for core developers who regularly compile from source. It allows you to easily associate your debug messages with a "channel" and with a "priority". This mechanism allows users to explicitly enable to certain log messages, while ignoring others. This can be helpful in order to troubleshoot certain problems.

Usage

Logging settings can be modified using the --log-level=[level] and --log-class=[class] command line options. Where level is one of the following:

  • bulk
  • debug
  • info
  • warn
  • alert
  • popup

And class is a white space seperated list of any (combination) of the following:

  • all
  • ai
  • enviroment
  • flight
  • etc.

For a complete list of available classes, see simgear/simgear/debug/debug_types.h.

If you are interested in simply logging certain properties to a file at runtime, you can use either FlightGear's built-in logging framework, or the generic protocol.

Related content

Wiki articles

Source code

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