Re: [Discuss-gnuradio] Out of Tree linker error... libgnuradio-MYMOD.so: undefined reference to `gr::fft::fft_complex::execute()'

[Marcus Müller]

Ah, by the way, look for gr-specest [1]; you can look at it as an
example of using gr-fft, fftw itself, some more gnuradio modules, and
the idyllic language called fortran in an out-of-tree module.

Greetings,
Marcus
[1] https://github.com/kit-cel/gr-specest
On 23.07.2014 22:36, Marcus Müller wrote:
> Hi John,
>
> I think you're on the right track:
> you use gr-fft in your code, but then don't tell your linker to link
> against that, which leaves your libgnuradio-comso missing the symbols
> from gr::fft, which breaks linking test-comso.
>
> So what you need to do is edit your CMakeLists.txt in your module's root
> dir and replace
> set(GR_REQUIRED_COMPONENTS RUNTIME)
> by
> set(GR_REQUIRED_COMPONENTS RUNTIME FFT)
>
> which will add the necessary linker directives, usually.
> Then you will need to add
>
>     ${GNURADIO_FFT_LIBRARY_DIRS}
>
> to your
> link_directories(...)
> further down.
>
> now, in your lib/ directory, edit the CMakeLists.txt
> and extend the  target_link_libraries(<yourmodule>...) directive with
>     ${GNURADIO_FFT_LIBRARIES}
>
> and do the same for the test-<yourmodule> target_link_libraries.
>
> Hm. Maaaybe we should be adding some more CMake magic, but then again,
> CMake is hard and mean :/
>
> Greetings,
> Marcus
>
> On 23.07.2014 22:24, John Murphy wrote:
>> I am getting a link error when making my Out-of-Tree module.
>>
>> I apologize in advance for the length of this, my first post to this list. I 
>> get the daily 'digest' version.
>>
>> This Out of Tree module was done with gr_modtool and cmake following the 
>> outline given in 
>> http://gnuradio.org/redmine/projects/gnuradio/wiki/OutOfTreeModules which, 
>> after some figuring out how my setup was missing some things, worked (make 
>> and install and runs in GRC) on another simpler block in this same module.
>>
>> This is a re-run of the make spew that fails to link:
>>
>> address@hidden build]$ make
>> Scanning dependencies of target gnuradio-comso
>> [  7%] Building CXX object 
>> lib/CMakeFiles/gnuradio-comso.dir/ofdm_rx_impl.cc.o
>> Linking CXX shared library libgnuradio-comso.so
>> [ 14%] Built target gnuradio-comso
>> Linking CXX executable test-comso
>> libgnuradio-comso.so: undefined reference to 
>> `gr::fft::fft_complex::execute()'
>> collect2: error: ld returned 1 exit status
>> make[2]: *** [lib/test-comso] Error 1
>> make[1]: *** [lib/CMakeFiles/test-comso.dir/all] Error 2
>> make: *** [all] Error 2
>> address@hidden build]$ 
>>
>> Note - it seems to me this is saying it linked my custom code to the fft but 
>> failed to link the test code? Or am I mis-reading this?
>>
>> I get the same error when I throw a #define switch in my block 
>> implementation header to directly use fft_impl_fft_complex instead of 
>> gr::fft::fft_complex. To make this work, such as it is, I had download the 
>> fft_impl_fft.h header file and edit as follows.
>> //#include <fft/api.h>
>> //#include <gr_complex.h>
>> #include <gnuradio/fft/api.h>
>> #include <gnuradio/gr_complex.h>
>> There may be a clue there, but I do not understand enough to know.
>>
>> Then here is the make error for this version, essentially identical.
>>
>> address@hidden build]$ make
>> Scanning dependencies of target gnuradio-comso
>> [  7%] Building CXX object 
>> lib/CMakeFiles/gnuradio-comso.dir/ofdm_rx_impl.cc.o
>> Linking CXX shared library libgnuradio-comso.so
>> [ 14%] Built target gnuradio-comso
>> Linking CXX executable test-comso
>> libgnuradio-comso.so: undefined reference to 
>> `fft_impl_fft_complex::execute()'
>> collect2: error: ld returned 1 exit status
>> make[2]: *** [lib/test-comso] Error 1
>> make[1]: *** [lib/CMakeFiles/test-comso.dir/all] Error 2
>> make: *** [all] Error 2
>> address@hidden build]$ 
>>
>> I run GNU Radio Comapnion with FFT GUI's and they work fine, so clearly 
>> something is executing FFT's although that may be unrelated. I do not have 
>> any problems, for now, with any In-Tree heir blocks or with any Out-Of-Tree 
>> blocks that do not link to the FFT libraries.
>>
>> Also, this block uses the get_inbuf() and get_outbuf() functions for the 
>> gnuradio fft classes, under either header mentioned above, with no linker 
>> issues reported.
>>
>> Module name is comso, block name is ofdm_rx, block is a C++ general-type 
>> block
>> I am running Fedora 20 with the LXDE desktop environment
>> GNU Radio is version 3.7.3 installed using yum from the default Fedora 
>> repositories
>>
>> linux kernel: 3.15.6-200.fc20.x86_64
>>
>> Some possibly-relevant Fedora packages already installed and latest version:
>> gnuradio-3.7.3-1.fc20.x86_64
>> gnuradio-devel-3.7.3-1.fc20.x86_64
>> fftw-3.3.4-3.fc20.x86_64
>> fftw-devel-3.3.4-3.fc20.x86_64
>> fftw-libs-3.3.4-3.fc20.x86_64
>> fftw-libs-single-3.3.4-3.fc20.x86_64
>> fftw-libs-double-3.3.4-3.fc20.x86_64
>> fftw-libs-quad-3.3.4-3.fc20.x86_64
>> fftw-libs-long-3.3.4-3.fc20.x86_64
>>
>> Anyone know what I need to do from here to make this build successfully? Am 
>> I still missing some file or something is still pointing to the wrong place?
>> Thanks.
>> -John
>>
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