Stream: t-compiler/const-eval

Topic: Time limits during const-eval

ecstatic-morse (Dec 12 2019 at 22:01, on Zulip):

With if available on nightly, and loop soon to follow, it's now feasible for users to write const initializers that will run long enough to trigger the infinite loop detector. We should discuss if/how we want to limit the amount of time spent during const-eval by default. I described one possible configuration mechanism in #67217, along with the set of defaults I would like to see.

ecstatic-morse (Dec 12 2019 at 22:06, on Zulip):

As I mention in the comments, I would like to have some way of disabling the infinite loop detector in the short-term, although I no longer think we need to block #67216 on it. It would be cool if we could decide on the interface for configuring time limits for const-eval relatively soon, and use that in the short-term to disable the loop detector, but it's not necessary.

ecstatic-morse (Dec 12 2019 at 22:09, on Zulip):

An alternative to a configurable limit is to have a fixed limit that is controlled by a long_running_const_eval lint. If you allow the lint, the infinite loop detector is disabled, and no limits are imposed on const-eval. If the lint is set to warn (the default), a warning will appear after that number of steps, and the infinite loop detector will start to trigger. If the lint is set to deny, reaching the fixed limit is a hard error.

RalfJ (Dec 14 2019 at 16:12, on Zulip):

TBH, I am not convinced the snapshot-based infinite loop detector is a good idea. IMO something simple like a basic-block-counter should be sufficient. But I won't block people if they want to go overboard with design here. ;)

RalfJ (Dec 14 2019 at 16:13, on Zulip):

However I'm afraid having both a fancy snapshot-based detector and a simple counter that interact in complex ways will be quite confusing.

oli (Dec 14 2019 at 16:15, on Zulip):

yea, I just thought the snapshot loop detector was a great idea for UX, but it's so much stuff for little gain...

oli (Dec 14 2019 at 16:15, on Zulip):

I'm fine with scrapping it

ecstatic-morse (Dec 16 2019 at 20:42, on Zulip):

I'm gonna open a PR removing the loop detector after #67260 gets merged.

RalfJ (Dec 22 2019 at 19:56, on Zulip):

I think this is the right move, but I'm also feeling bad because you put so much work into it.

Last update: Apr 05 2020 at 00:15UTC