RX channel out of range for configured RX frontends - c++

Question

I have a simple c++ test program on a Ettus x310 that used to work now doesn't. I'm trying to simply set two center freq of two channels of a single USRP. The above Out of range error occurs when I try to set anything on the 2nd channel.
I get a crash with a Channel out of range error:
$ ./t2j.out
linux; GNU C++ version 4.8.4; Boost_105400; UHD_003.009.001-0-gf7a15853
-- X300 initialization sequence...
-- Determining maximum frame size... 1472 bytes.
-- Setup basic communication...
-- Loading values from EEPROM...
-- Setup RF frontend clocking...
-- Radio 1x clock:200
-- Initialize Radio0 control...
-- Performing register loopback test... pass
-- Initialize Radio1 control...
-- Performing register loopback test... pass
terminate called after throwing an instance of 'uhd::index_error'
what(): LookupError: IndexError: multi_usrp: RX channel 140445275195320 out of range for configured RX frontends
Aborted (core dumped)
Here is my test program:
int main( void )
{
// sources
gr::uhd::usrp_source::sptr usrp1;
const std::string usrp_addr = std::string( "addr=192.168.10.30" );
uhd::stream_args_t usrp_args = uhd::stream_args_t( "fc32" );
usrp_args.channels = std::vector<size_t> ( 0, 1 );
usrp1 = gr::uhd::usrp_source::make( usrp_addr, usrp_args );
usrp1->set_subdev_spec( std::string( "A:AB B:AB" ), 0 );
usrp1->set_clock_source( "external" );
usrp1->set_samp_rate( 5.0e6 );
usrp1->set_center_freq( 70e6, 0 ); // this is OK
usrp1->set_center_freq( 70e6, 1 ); // crashes here With RX Chan out of Range Error!
printf( "test Done!\n" );
return 0;
}
The only thing Ive found so far in searching is make sure PYTHONPATH is set correctly (and for the heck of it I made sure it pointed to the site_packages) but again that seems to be related to GRC and not C++.
I am using Ubuntu 14.04.4 and UHD 3.9.1 with gnuradio 3.7.8.1 (Ive also tried 3.7.9.2) with the same result.
The hardware is an Ettus x310 with two BasicRx daughterboards.

Answer 1

Someone from the gnuradio/uhd Mailing List helped me. It appears that the vector initialization was wrong:
Replace:
stream_args.channels = std::vector ( 0, 1 );
With these two lines:
stream_args.channels.push_back( 0 );
stream_args.channels.push_back( 1 );
There are other more concise methods but this does the trick for now.
-Bob