TODO commentsΒΆ

Occasionally you may need to note a place in a file that needs to be revisited later. There are three standard codes used to designate such places: XXX, TODO, and BBB.

Depending on the type of the file, those codes should be placed within a comment according to the applicable syntax.


XXX comments should only be used during development to note things that need to be taken care of before a final (trunk) commit:

# XXX This will break if someone types `9`.

One should not expect to see XXX in released software.

It should be extremely rare to check in an XXX on a trunk. If an XXX is checked in on a trunk:

o The intention and expectation will be that someone will resolve
the XXX before someone releases the code.
o The XXX must fully describe an issue, so that someone else can
read the comment and know what it’s about.

XXX shall not be used to record new features, non-critical optimization, design changes, etc.


If you want to record things like new features, non-critical optimizations, design changes, or other long term changes, use TODO comments:

# TODO This could go faster if we'd use a better data structure.

People making a release shouldn’t care about TODOs, but they ought to be annoyed to find XXXs.


When adding code to preserve backward compatibility, use a BBB comment with a date. For example:

# BBB 2016-07-08, preserves use of 'get_foo' function