Fuzzer: Hang on inifinite define expansion

[veripoolbot]

---

Author Name: Eric Rippey
Original Redmine Issue: 1574 from https://www.veripool.org

Original Assignee: Wilson Snyder (@wsnyder)

---

Running the attached testcase with:

verilator_bin --lint-only 2.sv

On version:

Verilator 4.020 devel rev v4.020-40-gbaa6a2c

Produces no output, nor does it terminate in a reasonable amount of time.

[veripoolbot]

---

Original Redmine Comment
Author Name: Wilson Snyder (@wsnyder)
Original Date: 2019-10-29T02:35:36Z

---

Good & relevant one. It's basically this

`define e fun `e
`e

There's already two checks for recursive substitution, but these miss this because it's creating (infinite) output.
Added new error, hopefully won't have any false positives as there's some oddball huge defines in the real world.

 Too many preprocessor tokens on a line (>20000); perhaps recursive `define

[veripoolbot]

---

Original Redmine Comment
Author Name: Eric Rippey
Original Date: 2019-10-29T19:04:28Z

---

I'm glad this one was useful. I don't have a great procedure for figuring out what a minimal testcase looks like for hangs - hence this example being a little longer than what I normally aim for.