Re: Is there anything about USRP blocks that breaks them within hier blocks?

[Lukas Haase]

Dear Marcus, Dear Kevin,

On 2019-12-05 22:21, Kevin Reid wrote:
> On Thu, Dec 5, 2019 at 1:04 AM Müller, Marcus (CEL) <address@hidden
> <mailto:address@hidden>> wrote:
> 
>>     However, with your zero in- and output hier block,
>>     top_block.connect(something) was *never* called with the hier block,
>>     and hence, the hier block didn't become part of a flow graph that is
>>     to be executed. It's just a graph that *exists*, not one that *does*
>>     something.
>> 
>>     TL;DR: can't use a hier block without outside connections, since
>>     that's not becoming part of the top_block that'll be executed.
Wow, that was exactly the answer I was looking for.
I would have never guessed that.
I added a "Null Source" outside and a "Null Sink" inside and indeed, it works 
not as expected.
> In addition to the usual connect() that takes two blocks, there is also
> a connect() method overload that takes only one block, specifically to
> enable adding a block with no connections to a parent hier block or top
> block.
> https://www.gnuradio.org/doc/doxygen/classgr_1_1hier__block2.html#ab21892550c8fea3867628400bb8ed0be

Thank you.

> I just tested this case — GRC fails to generate an appropriate connect()
> call in the top block, but if I add one, then the blocks within the hier
> block execute as expected. I have filed
> issue https://github.com/gnuradio/gnuradio/issues/2950 about this.

Wonderful, thank you.

Luke