Re: [Discuss-gnuradio] Printing from c++ code

[Josh Blum]

My first guess is that you have gnuradio modules installed on more than 
one place in your system; older modules compiled without the printfs are 
being used, and the newer ones have second priority in the search path. 
Try a sudo make uninstall, and run your program, you should get errors.

My second guess would be that your work function is not getting called, 
or there is some conditional logic before the printfs. Try putting some 
printfs in the constructor of the block, just to prove to yourself that 
it prints on instantiation.


-Josh

David Knox wrote:
> I am unable to print from C++ code in gnuradio.  I have tried various
> combinations of included libraries and different types of print statements
> in my C++ code.  However, nothing that I have tried yet (see some attempts
> below) has let me see any output from the command terminal (where my printed
> python output appears).  I found an old response from Eric B. for a similar
> problem, but the offered solution did not work for me either.
>
> // #include <iostream>   // DAK
> #include <cstdio>
> // #include <stdio.h>   // DAK
> // #include <iostream> // DAK
> #include <cstring>
> .... 
>  fprintf(stdout, "\nTEST"); 
>  fprintf(stderr, "\nTEST");  
>  printf ("\nThis is a test"); 
>  fprintf(stderr, "Samples Processed: %d\n", d_processed), fflush(stderr);
>
> During the make/make install process (executed from the /src and /src/lib
> directories after my experimental changes; not sure where I'm supposed to do
> this).  I see errors if my C++ syntax is not correct, so presumably my
> changes are actually being compiled and I also see the corresponding object
> file times changing appropriately.  There could well be a problem with the
> importing of modules in python or C++ and/or my directory structure or
> paths.... sort of why I need the print statements to work in the first
> place.
>
> I don't claim to understand the hierarchy of python/swig/c++ calls or the
> autotools processes yet.  My basic task is to figure out the execution
> progress and sequencing of some routines written by others (which are a bit
> more complicated than the one in D. Shen's tutorial).  I want to understand
> the control flow for some ucla 802.15.4 extension code to gnuradio,
> specifically in the receive direction.  
>
> In general, how should/could standard I/O work out of a C++ program through
> SWIG into python?  Could someone tell me what is *supposed* to work (i.e.
> maybe the pertinent #include and (f)printf statements.  Alternatively, maybe
> someone could give alternatives to my primitive approach for understanding
> python/C++ program control flow and calling structure?  I have tried using
> the python interpreter and manually listing modules and module paths after
> each encountered import statement; pretty tedious.
>
> Presumably, there could be issues if C++ print statements get executed at
> the same rate as RF data is processed... but right now being swamped by
> print statement output from the signal processing code would be a welcome
> problem!
>
> Thanks, David