[myhdl-list] Re: MyHDL / ModelSim cosim

[Jan D. <ja...@ja...>]

David Brochart wrote:
> Jan,
> 
> I tried using one of the PLI C code you published for Icarus and running it with
> ModelSim. It works fine except that VSIM application gets bigger and bigger in

The fact that it works is good news. If the code works unchanged,
I could potentially continue to develop with Icarus (assuming its PLI
support is better by now) and just ask others (like you ;-)) to run
a regression check with Modelsim.

> the system, as if there was a memory leakage. I didn't notice it at the
> beginning but for very long simulations, which contain a lot of I/F signals
> between MyHDL and ModelSim (around 300), ModelSim just crashes.
> Have you noticed it with Icarus or CVER too? Any clue about the cause of it?

I haven't noticed this, but this doesn't mean a lot as I have never done
very long simulations to check this.

My guess is that it is a memory leak caused by the myhdl PLI code, not
by the simulator. This means that I should be able to reproduce it with
Icarus.

I have briefly looked at the code and I can see potential memory leaks:

- apparently call back handles should be explicitly freed with a special
vpi call after registering;
- at a certain point the code malloc's memory in a callback which is
never freed.

As callbacks are created all the time during simulation, this could
explain it. I will run a check with Icarus to see if I can
reproduce/resolve the issue.

> Also, you said some time ago that you were able to use a ModelSim license. Have
> you made some progress? 

To be honest not - during the past months I have been able to spend
much less development time than anticipated. The time I had was spent
on improving the "infrastructure". I want to make it much easier
for others to participate in the project (especially website and
documentation) so that it depends less on me (and my delays :-)).
Nothing released yet, but it will become much better.

 > Do you plan to release a VHDL PLI for using MyHDL with
> ModelSim in the near future?

I want it definitely. After releasing the new website, this will
be my first goal. I'm not sure wether I'll still have access,
if it is really true that the code from Icarus works unchanged,
there may be other possibilities as suggested earlier.

Jan

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