- Production-grade parser.
- Just-in-time compiler (JIT), allowing e.g. calls into libraries without wrappers.
- Modular C++ API from the ground up.
- Separate parser and execution engine.
- C++ 11... support through clang.
We have announced cling to the public in 2011. cling is in production use by CERN; bugs should be reported to the ROOT project here.
We even have doxygen documentation of cling's code.