Would be nice if most or all of our C++ code generators used the same tool. That tool, rather than arbitrary python generating arbitrary Cxx, could have a very fixed form similar to the generate_error_codes.py generator.

Proposal: all inputs (if any) are yaml, which generates python objects.
These objects are passed to Cheetah, which fills in a template file that looks a lot like a PHP template that produces Cxx. So there's not much arbitrary execution. The yaml is declarative, and the cheetah is usually very simple. There isn't a big layer of python to understand, and devs can edit these templates easily as Cxx-like files.

Something like idlc might not need to be very big. What it's doing might very well be doable as a yaml file + Cheetah template.

There may be some yaml->yaml transformation stages if the source yaml needs to be massaged or verified, but that's an easier program to analyze than a program that emits Cxx statements in Python code.