Re: [Discuss-gnuradio] Reconfiguring OFDM flow graph at run time gives "FATAL: Missing a required length tag on port 0 at item" error

[Kevin Reid]

On Sat, Dec 24, 2016 at 9:46 AM, Damindra Bandara <address@hidden> wrote:

Also, I get the error only when I try to reconfigure a flow graph. Could you please let me know the correct way to reconfigure a flow graph when they are using tags.

Both reconfiguration and tags are lesser-used features (reconfiguration even less), and based on my experience with reconfiguration, there might well be a bug in a particular block's interaction with reconfiguration. I would suggest taking a troubleshooting/debugging approach to finding out what is sufficient to cause the problem:

• Does it happen if you only stop and start the flow graph without actually changing any connections?
  
  
• Does it happen if you lock(), change, unlock() — instead of stop(), change, start()?
  
  
• Does it happen if you do some reconfiguration but less than your application actually needs — e.g. replace a block with a newly-constructed identical block (should have no effect)?

It would be great if (if there actually is a bug here) you can narrow it down to a simple example and file a bug report.

I might be able to help with the narrowing down if you have some reasonably-sized Python/GRC code you could share, as I've gone through this process several times. (I develop a reconfiguration-heavy application.)