Setting an execution limit

[James Lovejoy]

Hi,

Is there a way to set a hard execution limit in the V8 engine? I want to be able to prevent things like infinite loops and recursions. I realise that since V8 compiles to machine code I don't get a program counter or anything. I feel like setting the "stack limit" is the right way to go but the usage of this feature from the documentation is unclear. Can someone guide me as to how to achieve such a limit?

James

[Ben Noordhuis]

If 'execution limit' means 'time limit': start a watchdog thread and
call v8::Isolate::TerminateExecution() from that thread on timeout.
It must be a thread, it's not safe to call from a signal handler.

[James Lovejoy]

Really I need something a little more deterministic than a time limit. Is there a way to set an instruction limit? Or perhaps something similar to lua_sethook (http://pgl.yoyo.org/luai/i/lua_sethook) in Lua which calls a callback every given number of instructions.

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[tbl...@icloud.com]

I don't think there's any way. V8 JavaScript code is compiled to native code, and no instrumentation is really possible on that.

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[Jakob Kummerow]

There is always a stack limit, which always prevents infinite recursion; as well as, in fact, finite but very deep recursion.

As Ben said, the only way to prevent infinite or long-running loops is by interrupting the program from another thread. You may have heard of the Halting Problem, TL;DR: there really can be no other way, because in the general case it is impossible to predict whether a loop will terminate at all, and how soon.

There is no way to set a limit for executed instructions. You could hack it, but it's going to be non-trivial.

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