[Vm-dev] Is it possible to compile stack vm without heartbeat?

Eliot Miranda eliot.miranda at gmail.com
Sat Sep 10 05:18:22 UTC 2011

Hi Javier,

On Fri, Sep 9, 2011 at 5:49 AM, Javier Pimás <elpochodelagente at gmail.com>wrote:

> Hello guys, we've been working in porting the stack vm to native client,
> and we found that signals are not (yet?) supported. Because of that it's not
> possible to compile the sqheartbeat.c file. Is there any way to avoid having
> to compile it? Because the old interpreter could live without it...

Well, yes its possible if you're prepared to modify the activation code to
check for an event counter, but you really, really don't want to do that.
 Preferrably you need to find an alternative.  One way is by a timer
callback, and another way is via a thread looping on a delay.  Which you
choose depends on the platform.  On linux we use a timer callback
implemented using setitimer and signal, but only because linux doesn't
current;y support multiple thread priorities in user processes.  On Mac and
Windows we use a high-priority thread looping on a delay, by far the more
preferrable method.  The real question to ask is "What are the timing and
threading facilities provided by NaCl?".  So what does it provide in terms
of timer callbacks, delays and multiple threads?  If the answer to all of
these is "nothing" then you'll be forced to go with an event counter, with
its attendant performance and latency problems.  ALternatively, if NaCl does
provide either delays and multiple threads or timer callbacks, then
implement the heartbeat in terms of those facilities.


> Cheers,
> Javier.
> --
> Lic. Javier Pimás
> Ciudad de Buenos Aires

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