[Discuss-gnuradio] Trouble With UHD Tune Request

Hello,
I'm working on a C++ block which accepts a pointer to a uhd sink and
calls the sink's set_center_frequency method to change to a new
frequency. Set_center_frequency requires input in the form of a
uhd::tune_request_t and returns a uhd::tune_result_t. As a bit of
background, I generated an out of tree module with gr-modtool.py. It
contains this block as well as two other blocks. The other blocks can be
used in GRC but this on cannot as it requires a pointer, so I disabled
the installation of its xml file in grc/CMakeLists.txt and will be using
it exclusively through c++. The issue that I am having seems to be in
accessing the libraries for UHD.

//My call to set_center_frequency, where private_UHD_Sink is a pointer
to a UHD Sink and private_freqs is a pointer to the first member of an
array and current_freq sets the index of the array
uhd::tune_result_t result_sink =
private_UHD_Sink->set_center_freq(uhd::tune_request_t(*(private_freqs +
current_freq)));

I first compiled my flowgraph without #including <tune_result.hpp> and
<tune_request.hpp> in my source file. Surprisingly, things compile just
fine without the two files. However, a c++ flowgraph which tries to use
the block gives a nondescript error ("expected primary-expression before
'('") on the line which instantiates my block. Using one of the other
blocks (which share the same module) in GRC returns "ImportError:
/usr/local/lib/libgnuradio-DL_Hitemp_Blocks.so: undefined symbol:
_ZN3uhd14tune_request_tC1Ed".

I then thought that I would try to include the two files mentioned
above, and of course it refused to compile because it could not find the
files. I looked at the CMakeLists.txt file included with the tag demo
c++ example included in gnuradio and decided to add
include_directories(${UHD_INCLUDE_DIRS}) and
link_directories(${UHD_LIBRARY_DIRS}) to my CMakeLists.txt file in my
src directory. The issue seems to be that many of the cmake directory
variables on my system were not set properly. Adding "MESSAGE(STATUS,
"GR include path: ${GNURADIO_CORE_INCLUDE_DIRS}")" to my CMakeLists.txt
file produces "STATUS,GR include path: /usr/local/include/gnuradio" but
this is the only GNUradio related cmake variable I have found that seems
to have been set properly. Adding "MESSAGE(STATUS, "UHD include path:
${UHD_INCLUDE_DIRS}") MESSAGE(STATUS, "UHD include path:
${UHD_LIBRARY_DIRS}")" produces "STATUS,UHD include path: STATUS,UHD
include path: ". I was able to get the source to compile by setting the
UHD include path absolutely (added
"include_directories(/usr/local/include/uhd/types)" to my CMakeLists.txt
file - but I can't seem to find the UHD_Library_Directory so I cannot
try setting it absolutely. The program now compiles, but the same error
is produced in GRC as well as in the c++ flowgraph. I am wondering if
anyone has any idea how I could go about including the appropriate UHD
libraries or what else could be causing these errors? Thanks ahead of time!

--
Dan

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