Code Generators or T4 Templates, are they really evil?

Question

I have heard people state that Code Generators and T4 templates should not be used. The logic behind that is that if you are generating code with a generator then there is a bet

Answer 1

It seems to me code generators are fine as long as the code generation is part of your normal build process, rather than something you run once and then keep its output. I add this caveat because if just use the code generator once and discard the data that created it, you're just automatically creating a massive DRY violation and maintenance headache; whereas generating the code every time effectively means that whatever you are using to do the generating is the real source code, and the generated files are just intermediate compile stages that you should mostly ignore.

Lex and yacc are classic examples of tools of allow you to specify functionality in an efficient manner and generate efficient code from it. Trying to do their jobs by hand will lengthen your development time and probably produce less efficient and less readable code. And while you could certainly incorporate something like lex and yacc directly into your code and do their jobs at run time instead of at compile time, that would certainly add considerable complexity to your code and slow it down. If you actually need to change your specification at run time it might be worth it, but in most normal cases using lex/yacc to generate code for you at compile time is a big win.