Re: [ft-devel] endless loops in bytecode

[Roland Mainz]

On Mon, Sep 12, 2016 at 4:09 PM, Alexei Podtelezhnikov
<address@hidden> wrote:
> On Sat, Sep 10, 2016 at 1:38 PM, Werner LEMBERG <address@hidden> wrote:
>> do you have any ideas how to discover endless loops in bytecode that
>> don't change the nesting level?
>>
>> My only idea up to date is to count JMPR, JROT, and JROF separately,
>> using a threshold of, say, 10000.
>
> It turns out this is a famous CS topic:
> https://en.wikipedia.org/wiki/Halting_problem
>
> So your idea of counting jumps is cheap and reasonable. I would run a
> total jump count of any kind though and stop after 1000 jumps of any
> kind. Enough is enough.The bytecode length is limited to 65536 (no?).
> In the worst case scenario, 1000 jumps will produce 65 million
> instructions. Perhaps, the total jump count should be even smaller,
> like 100.

I'd go more for a limit like 0xFF or 0xFFF. IMHO a jump count of "100"
is far too small...

----

Bye,
Roland

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