In my gnuradio test application I’m attempting to pass a JSON formatted string from my C++ custom block, to my python flow graph containing the block.
The String message are being received by my python flow graph, but there’s a memory leak. Over time, my flowgraph RSS (memory footprint) grows at about 32k/s up until the application runs out of memory. The leak didn’t start until after I retrofitted my flowgraph and custom block with polymorphic type (PMT) based message passing. I’m passing a 200 or so byte JSON string (as a symbol) from C++ block to python flow graph about 60 times per second. Sleuthing through the pmt.cc code [1] I see the String (symbol) objects are stored in a hash. I suspect what is happening is that since all of my JSON strings are unique, they’re getting added to the hash and causing the hash to grow unbounded over time. >From what I can tell by reading the wiki [2], the approach I’m using is the best way to get a string from my custom block and into my python flowgraph. [1] https://github.com/gnuradio/gnuradio/blob/master/gnuradio-runtime/lib/pmt/pmt.cc [2] https://www.gnuradio.org/doc/doxygen/page_pmt.html Sample c++ block code snippet from my work function: // Calculate metrics. Occasionally (60/second) we'll get back a JSON formatted string of metrics. crossingData = calculateWaveCrossingMetrics(lastSampleValue,in[i]); if (crossingData.length() > 0) { pmt::pmt_t messageString; messageString = pmt::string_to_symbol(crossingData.c_str()); message_port_pub(polymorphicMessageDestination, messageString); Questions: 1. Is this the best way to get a string from my C++ block into my python application? 2. Is there a way to pass my messages that doesn’t result in memory growing unbounded? Thank you Brad
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