API review

Proposer: Josh Faust

Present at review:

• List reviewers
  • Eric
  • Brian
  • Rob
  • Tully
  • Conor
  • Jeremy

Question / concerns / comments

For reviewers: Enter your thoughts on the API and any questions / concerns you have here. Please sign your name. Anything you want to address in the API review should be marked down here before the start of the meeting

Brian:

• How are output handlers added? In particular, how does output get routed to rosout?
• How is verbosity level determined externally? Environment variables, cmdline args?
• Do we know which compilers don't support variadic macros?

Conor:

• Could we provide an enablement scheme that is symbolic based on expression matching in addition or instead. Provides higher fidelity in targetting debug output, and avoid arbitrary thresholding decisions

• Usage: ROS_DEBUG(MyPackage.Scoped.Name, foo.output().str() << ":" << this doubleValue << " Is not what is epxected");

• Enabled by a configuration input such as MyPackage*

• An implementation of this kind of scheme could be pulled from EUROPA library code.

• Also supports conditional debug output, when enabled: ROS_COND_DEBUG(!expectedSuccessValue, MyPackage.Scoped.Name, foo.output().str() << ":" << this doubleValue << " Is not what is epxected");

• Should make sure the cost when not enabling a debug message is neglible.

Rob:

• I don't like the idea of exposing log4cxx:Level in the API for ROS_LOG
• Why is g_logger public if getLogger() is supported?
• Can ROS_INFO, ROS_DEBUG, etc... be implemented as calls to ROS_LOG?
• Does ROSCONSOLE_AUTOINIT work as implemented (naked call to initialize())?

Meeting agenda

• Brief overview of log4cxx (http://logging.apache.org/log4cxx/index.html). Should answer:

  • How are output handlers added? In particular, how does output get routed to rosout?
  • Could we provide an enablement scheme that is symbolic based on expression matching in addition or instead. Provides higher fidelity in targetting debug output, and avoid arbitrary thresholding decisions

  • Usage: ROS_DEBUG(MyPackage.Scoped.Name, foo.output().str() << ":" << this doubleValue << " Is not what is epxected");

  • Enabled by a configuration input such as MyPackage*

• Should make sure the cost when not enabling a debug message is neglible.
• Rob: I don't like the idea of exposing log4cxx:Level in the API for ROS_LOG
• Why is g_logger public if getLogger() is supported?
  • To avoid the function call (worth it?)
• Can ROS_INFO, ROS_DEBUG, etc... be implemented as calls to ROS_LOG?
  • Yes
• Conditional output
  • Yes, we can support this
• Does ROSCONSOLE_AUTOINIT work as implemented (naked call to initialize())?
  • Yes
• Do we know which compilers don't support variadic macros?
  • Do support: The GNU Compiler Collection, since 3.0, C++Builder 2006 and Visual Studio 2005 [1] support variable-argument macros, both when compiling C and C++ code (wikipedia)
  • If we want to support gcc 2, it supports an alternate syntax
• Possibly pull assertions into this library?

Minutes

• Use log4cxx calls directly to add appenders
• Don't wrap log4cxx calls; let the user (in many cases, ros::node) call them directly. Allows for easier interaction with other applications /
  • libraries that use log4cxx.
  • Design goal is to hide log4cxx from most users
• log4cxx allows hierarchical loggers, each with its own verbosity level
• Conor wants symbolic debug "levels," with efficient symbol matching to
  • determine which ones are actually output.
• Support for "foo*" is needed, but "*foo" is probably not.

TODO

• Add ROS_WARN_NAMED() that takes a symbol name for the message.
  • ROS_WARN() uses a default name of the package name itself.
• Add COND variations.
• Implement STREAM variations.
• Implement static enable-checking.
• Within ros::console, define enum of levels, which essentially typedef to
  • log4cxx levels.
• To work well with 3rd-party packages that also use log4cxx, add our
  • appenders to our own logger, rather than the root logger.
    • Potentially provide a mechanism within ros::node to adding our
      • appenders to somebody else's logger.
• Pull assertions ROS_ASSERT and ROS_BREAK into rosconsole
  • Eventually add new stuff like breaking within debugger.

Conclusion

Package status change (also mark change on PackageStatusDict page)

• Action items that need to be taken.

• Major issues that need to be resolved

Conditional pass.

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