[Discuss-gnuradio] block::system_handler done message format

[Jared Dulmage]

As I was investigating the message passing subsystem I noticed that my own 
blocks had a "system" port that I did not manually register.  Looking through 
the code I found in block.cc the special message to put the block in a finished 
state:

void
  block::system_handler(pmt::pmt_t msg)
  {
    //std::cout << "system_handler " << msg << "\n";
    pmt::pmt_t op = pmt::car(msg);
    if(pmt::eqv(op, pmt::mp("done"))){
        d_finished = pmt::to_long(pmt::cdr(msg));
        global_block_registry.notify_blk(alias());
    } else {
        std::cout << "WARNING: bad message op on system port!\n";
        pmt::print(msg);
    }
  }

Maybe I don't understand the reason for this, but it appears that this code 
requires pmt::cdr(msg) to return a long int and then implicitly casts to a 
bool.  Wouldn't it be better for this to be a bool already such that a message 
could be constructed like

pmt::cons(pmt::mp("done"), pmt::get_PMT_T())

or Python

pmt.cons(pmt.to_pmt("done"), pmt.PMT_T)  ?

Perhaps it really doesn't matter.  It just seems more natural, particularly if 
one were to put a logical statement as the argument to pmt::cons.

Jared.
------------------------------------------------------
Jared Dulmage
Engineering Specialist
Digital Comm. and Implementation Dept.
Aerospace Corporation
310-336-3140