Does fill() create equations?

[Volker Waurich]

Hi,

In Modelica_DeviceDrivers, there is a Serialpackager class which gets a Modelica_DeviceDrivers.Packaging.SerialPackager model as an input and then, passes this object via a connector to the attached Serialpackager. These packages are meant to be the same object/variable/memory among all connected SerialPackagers. There is no alias equation in the model, only:

if nu == 1 then
    pkgOut.pkg = fill(pkgIn.pkg, nu);

The frontend does not create any alias equation which matters since these are external objects.
What is needed here, is the equation: pkgOut[1].pkg = pkgIn.pkg
This is not the case. Can you reveal this information somehow?
I will care of the backend stuff.

[Volker Waurich]

{fill()} does create alias equations for non-external objects. Only for external objects, its missing.

[Adrian Pop]

I'll look into it.

[Adrian Pop]

​PR1194 should fix this, running it now.

[Adrian Pop]

Fixed the frontend part in 20336d/OMCompiler. Added test in 8898d5/OpenModelica-testsuite.
@vwaurich: take it away.

[Volker Waurich]

Thanks for the very quick fix.

[Martin Sjölund]

Except you are not allowed to create aliases or assignments to external objects and this should simply not work in a Modelica compiler...

[Bernhard Thiele]

Well, if it can work, I think it should work. It is really useful even if it is not perfect. Maybe we figure out a better way to achieve the same in the future, but for moment I really appreciate that there is a drive to support that feature also in OMC.

[Volker Waurich]

@sjoelund Is there a reference about it? I would like to add a notification if external objects are assigned an alias.

[Martin Sjölund]

Spec says:

Only the constructor may return external objects and external object can only be bound in component declarations and neither modified later nor assigned to.

I guess inner/outer could possibly be a shared external object, but not connections :(

I would have made it an error that tells the user to enable debug-flags for this behavior to be supported (and only allow it for connections or alias equations, not bindings or assignments).

See also: ​https://trac.modelica.org/Modelica/ticket/1669

[Volker Waurich]

Thanks for the info.
Shall we name the flag "+d=allowExternalAlias" or "+pedantic=false" ;)
Anyway, I am glad that OMC supports this for now.

[Adrian Pop]

If we can do more than the specification says, I don't see a reason why we should not do it.
We can give warnings for these things but I think we should support this by default.

[Bernhard Thiele]

I completely agree.

[Volker Waurich]

I added a warning and will close the ticket.