RDoc is, or was, the de facto standard for producing documentation from code comments embedded inline in Ruby and C extension code. At the time of writing (October 2010) it is rapidly being displaced by superior alternatives such as YARD.
Principal criticisms of RDoc include:
- stagnated development
- ugly default output
- brittle parser extremely sensitive to input variation
- large disparity between capabilities of Ruby parser and C parser, making documentation for C extensions in C files basically infeasible
- inadequate escaping options