RtAudio

Some checks for return codes are missing.

Examples:
Would you like to add more error handling for return values from
"pthread_mutex_init" like in the RtApi constructor and from
"jack_set_process_callback" in the member function
"RtApiJack::probeDeviceOpen"?
http://rtaudio.svn.sourceforge.net/viewvc/rtaudio/trunk/RtAudio.cpp?revisio
n=45&view=markup