[Discuss-gnuradio] New dsp block: no constructor defined

[LianFeier]

Hi!

I'm writing a signal processing block with gr-modtool. I've successfully make. 
When I try ctest -V, I get the "No constructor defined" error. The swig 
interface file which gr_modtool generates is like:

/* -*- c++ -*- */

#define myblock_API

%include "gnuradio.i"            // the common stuff

//load generated python docstrings
%include "myblock_swig_doc.i"

%{
#include "myblock/myclass.h"
%}


%include "myblock/myclass.h"
GR_SWIG_BLOCK_MAGIC2(myblock, myclass);

I've seen some threads that said swapping the last two lines would help, but in 
my case it didn't. I'm using the latest version of gr-modtool(it generates 
xx_impl.cc,xx_impl.h and xx.h), and my gnuradio version is 3.6.0.

Could anybody kindly help?

Update:
I've tried with the simplest gr-howto block, it failed too. So I guess this 
error is not due to my c++ code?

ERROR: test_001_t (__main__.qa_square_ff)
2: ----------------------------------------------------------------------
2: Traceback (most recent call last):
2:   File "/home/gnu/gr-howto/python/qa_square_ff.py", line 37, in test_001_t
2:     sqr = howto.square_ff()
2:   File "/home/gnu/gr-howto/build/swig/howto_swig.py", line 161, in __init__
2:     def __init__(self, *args, **kwargs): raise AttributeError("No 
constructor defined")
2: AttributeError: No constructor defined

Regards and thanks,
Fei