On: Parsing Awk Is Tricky

[thomasmg]

> Hand-rolling has a bunch of pitfalls

I'm arguing that this is not the case in reality, and asked for concrete examples... So again I ask for a concrete example... For memory corruption, there are plenty of examples.

For parsing, I know one example that lead to problems. Interestingly, it was about using a state machine that was then modified (manually) and the result was broken. Here I argue that using a handwritten parser, instead of a state machine that is then manually modified, would not have resulted in this problem. Also, there was no randomized testing / fuzz testing, which is also a problem. This issue is still open: https://issues.apache.org/jira/browse/OAK-5367

[tgv → thomasmg]

There's no reason for concrete examples, because the point was about the fundamental misguidedness of parser generators, not about problems with individual parser generators or the nice things you can do in a hand-rolled one, but to accommodate you, ANTLR gives one on its home page: "... At Twitter, we use it exclusively for query parsing in Twitter search... Samuel Luckenbill, Senior Manager of Search Infrastructure, Twitter, inc."

Also, regexps are used very often in production, and that's definitely a parser-generator of sorts.

The memory corruption example was an analog, but to spell it out: it's easier and faster to write a correct parser using flex/bison than by hand, especially for more complex languages. Parser-generators have their use, and are not fundamentally misguided. That you might want to write your own parser in some cases does not diminish that (nor vice versa).