Method on Isolate to check for interrupts

[Noa]

Hi all,

I'm using `v8::Isolate::TerminateExecution` for a couple of different things, and am trying to make sure that execution will stop as soon as possible after it's requested. In one place, we call TerminateExecution inside of a host function, in the context of a HandleScope, and I'd like to make sure that execution doesn't continue in JS after that function returns (currently, `IsExecutionTerminating() == false` directly after calling TerminateExecution). I also want to check that there's no execution termination in-queue at the start of the call of a host function.

Looking at the v8 source, it seems like `v8::internal::StackGuard::HandleInterrupts` (or perhaps `v8::internal::StackLimitCheck::HandleStackOverflowAndTerminationRequest`) would be the ideal function to call in both of these situations, but neither are exposed in the public API. Would it be reasonable to expose a `v8::Isolate::HandleInterrupts` method that would forward to one of those internal functions?

Alternatively, my first case could be fixed by a non-thread-safe `v8::Isolate::TerminateExecutionNow`, which directly calls `v8::internal::Isolate::TerminateExecution` (i.e, `Throw(termination_exception)`). This would be nice to have, but not fundamentally different from `TerminateExecution(); HandleInterrupts()`.

In any case, I'd be willing to submit a patch implementing this method, if that would be welcomed.

Best,
Noa

[Erik Corry]

The stack guard should be checked on every call and on every back edge
of a loop in JS, so it should be happening quite fast. Are you seeing
that it doesn't immediately stop when you return to JS?

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Erik Corry, working on V8 at Cloudflare

[Noa]

I don't think that's been observed, so I guess my coworker just wrote
this part of our code not knowing the frequency at which the interrupt
flag is checked. It'd kind of be nice as a user to have a guarantee,
since there's no way to know for sure that v8 is inserting those
interrupt checks, though I suppose it is indeed a pretty safe assumption
that there would be a stack check on every call. If what you say is
true, I guess we don't actually have a need for this, so thank you. (I
do still think it'd be a reasonable API to provide for e.g. recursive or
long-running host calls.)

Noa, they/she
github.com/coolreader18