My experience with Faust, and some more general observations

OK. I copied render.cpp to the IDE and set the cmd line parameters. Result:

Building render.cpp...
Makefile:411: recipe for target '/root/Bela/projects/faust/build/render.o' failed
Build finished
variable type 'BelaUI' is an abstract class column: 8, line: 310

which is

...
dsp* fDSP;
BelaUI fUI;
bela_midi fMIDI;
MidiUI* fMidiUI;
...
/usr/local/include/faust/gui/UI.h:71:22: note: unimplemented pure virtual method 'addSoundfile' in 'BelaUI'
        virtual void addSoundfile(const char* label, const char* filename, Soundfile** sf_zone) = 0;

seems the code was too old to be compiled. Got the latest bela.cpp from git and now, this results:

/**************************BEGIN USER SECTION **************************/

<<includeIntrinsic>>

<<includeclass>>

/***************************END USER SECTION ***************************/

/*******************BEGIN ARCHITECTURE SECTION (part 2/2)***************/

std::list<GUI*> GUI::fGuiList;
ztimedmap GUI::gTimedZoneMap;

/**************************************************************************************
  Bela render.cpp that calls FAUST generated code
***************************************************************************************/

unsigned int gNumBuffers = 0;   // the number of de-interleaved buffers for audio and analog i/o
FAUSTFLOAT *gInputBuffers = NULL, *gOutputBuffers = NULL; //de-interleaved input/output buffers for the audio and analog inputs
FAUSTFLOAT* gFaustIns[10];      // array of pointers to gInputBuffer data
FAUSTFLOAT* gFaustOuts[10];     // array of pointers to gOutputBuffers data
mydsp fDSP;

Any idea, what's missing (sorry, I have no idea about faust infrastructure, because I can't get it to work neither offline or online).

So I decided to compile faust.dsp with faust and inserted the created cpp code into bela.cpp (i.e. render.cpp). Result now:

Building project...
Building render.cpp...
 ...done
Linking...
 ...done
Build finished
Running project...
/root/Bela/projects/faust/faust: unrecognized option '--faust'
Usage: 

Am I missing something important here?

I have no problems with pre-compiled dsp code and to include that. But somehow the generated program doesn't run:

After some editing , copying session, I came to this point:
Building project...
Build finished
Running project...
Trying to parse FAUST file: (null)
Error: no audio callback defined. Make sure you set settings->render to point to your audio callback
Error: unable to initialise audio
Makefile:502: recipe for target 'runide' failed
make: *** [runide] Error 255
Bela stopped

I can't see any settings->render. Please advise.

After adding these lines:
settings.setup = setup;
settings.render = render;
settings.cleanup = cleanup;
to main.cpp, I got no error left, but also no sound. And no GUI. Do I need anything else?
I can hear, that the audio is switched on and off, but that's it.

Does this message mean anything: Trying to parse FAUST file: (null)
When I stop Bela:
Error in `/root/Bela/projects/nfaust/nfaust': corrupted size vs. prev_size: 0x00803840
Aborted
Makefile:502: recipe for target 'runide' failed
make: *** [runide] Error 134
Bela stopped

giuliomoro : yes, the flute example needs a GUI action. My folder (nfaust) is actually the same as your github folder. I replaced the main.cpp with the mentioned code and render.cpp with the bela.cpp code. In render.cpp I added $include "faust.,h", which contains the compiled faust.dsp code. That's it. If you want, I can upload the whole project. But without GUI, Faust is meaningless.
Any idea, what's the problem with the GUI is?

To activate HTTP UI control you will have to follow what is done in other architecture files, like : https://github.com/grame-cncm/faust/blob/master-dev/architecture/jack-qt.cpp

So adding in the bela.cpp template file:

#include "faust/gui/httpdUI.h"

 httpdUI httpdinterface(name, fDSP.getNumInputs(), fDSP.getNumOutputs(), argc, argv);
 fDSP.buildUserInterface(&httpdinterface);
 ...
httpdinterface.run(); 

Then you'll have to compile the code in faust source tree: /architecture/httpdlib and link also with libmicrohttpd (https://www.gnu.org/software/libmicrohttpd/)

Then starting the program will start a libmicrohttpd based server at http://127.0.0.1:5510, that should display the UI to control the DSP running on the Bela card.

A bit of work but not impossible...

Do you mean render.cpp (instead of bela.cpp)?
I found a gem: if (p == '.' | p == ',') (really?) ;-)

So, I got the /root/faust/architecture/httpdlib/cmake/libHTTPDFaust.so, how do I have to link this to the bela project?
(I guess, I have to change the Makefile, but what will be the code for including the shared lib)?

I finally got around adding the so file, but now I'm lost (again):
/root/faust/architecture/httpdlib/cmake/libHTTPDFaust.so: undefined reference to jsscripts_len'
/root/faust/architecture/httpdlib/cmake/libHTTPDFaust.so: undefined reference tostylesheet_len'
/root/faust/architecture/httpdlib/cmake/libHTTPDFaust.so: undefined reference to stylesheet'
/root/faust/architecture/httpdlib/cmake/libHTTPDFaust.so: undefined reference tojsscripts'

This variables are defined as 'extern', but in what library?
This is the line in Makefile, I'm using:
LDFLAGS += $(DEFAULT_XENOMAI_LDFLAGS) -Llib/ -lasound -lsndfile -lseasocks -L/root/faust/architecture/httpdlib/ -lHTTPDFaust /root/faust/architecture/httpdlib/cmake/libHTTPDFaust.so