Block without work function won't stop

Hi all,

I have a block that is used only for acepting messages and writing their
content into database. The block is written in python and it has no work
function, but only constructor and message handler. However when I run
flowgraph it won’t finish until I terminate it. When I exclude this
it runs to completion normally.
Is there any issue with messages in this case. Should I manually delete
messages from the message queue or something like that.



thank you Marcus for your fast answer. Well, the problem is that nobody
ecept scheduler knows when the flowgraph has finished, so I don’t know
should sent that message to the block. This is however not of crucial
importance for me. Namely I wanted to test some of my custom blocks, and
test flowgraph necever reached completion, but as soon as message
dummy block was out everything was fine.


On Tue, May 26, 2015 at 2:29 PM, Marcus Müller
[email protected]

Hi Nemanja,

the point is that with message passing, it’s not clear that your block
is ever finished.
Hence in, we have a mechanism to retrieve the “finishedness” of
a pure-message-block.

if((detail()->ninputs() != 0) || (detail()->noutputs() != 0))
return false;
return d_finished;

So, you’ll have to set the d_finished variable of your block; sadly,
that’s a private one by design (I think there are thread-safety reasons
this is not directly exposed, but I’m not sure – I’d have to as T[io]m
about that).
The proper way to do so is to send your block a message to its
pmt::mp(“system”) port, containing pmt::mp(“done”).

Best regards,


my workless function block blocks my flowgraph when I call unlock(). I
a method where I set d_finished to True, but this doesn’t help.


Hello again,

could you please Marcus, or somebody else, give me some hint for sending
done message to a block’s “system” port. Are all blocks by default
subscribed to system port?


Huh, I’m out of my depth here.
However, yes, every subclass of gr::block automatically has a
pmt::mp(“system”) message port, that you can use to do such things.

Best regards,