# Newbie problem

**URL:** <https://www.ruby-forum.com/t/newbie-problem/234252>\
**Category:** GNU Radio\
**Created:** [February 18, 2015, 10:14pm UTC](https://www.ruby-forum.com/t/newbie-problem/234252 "2015-02-18T22:14:31Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [February 18, 2015, 10:14pm UTC](https://www.ruby-forum.com/t/newbie-problem/234252/1 "2015-02-18T22:14:31Z")

</div>

I was excited to successfully try an rtl-sdr GRC demo/tutorial and  
decided to start following the gnuradio tutorials to better learn the  
program. I quickly ran into trouble, so am sure I’ve done something  
stupid but can’t figure out what! Running through tutorial

[http://gnuradio.org/redmine/projects/gnuradio/wiki/Guided\_Tutorial\_GRC](http://gnuradio.org/redmine/projects/gnuradio/wiki/Guided_Tutorial_GRC)

and reaching section 2.2.3, ‘Generate’ goes fine, but not ‘Execute’:

Generating: “/home/mm/gnuradio/tutorial\_two\_1.py”

Executing: “/home/mm/gnuradio/tutorial\_two\_1.py”

Traceback (most recent call last):  
File “/home/mm/gnuradio/tutorial\_two\_1.py”, line 13, in   
from gnuradio import qtgui  
File “/usr/lib/python2.7/site-packages/gnuradio/qtgui/ **init**.py”,  
line 34, in   
from qtgui\_swig import \*  
File “/usr/lib/python2.7/site-packages/gnuradio/qtgui/qtgui\_swig.py”,  
line 28, in   
\_qtgui\_swig = swig\_import\_helper()  
File “/usr/lib/python2.7/site-packages/gnuradio/qtgui/qtgui\_swig.py”,  
line 24, in swig\_import\_helper  
\_mod = imp.load\_module(‘\_qtgui\_swig’, fp, pathname, description)  
ImportError: /usr/lib/libgnuradio-qtgui-3.7.6.1.so.0.0.0: undefined  
symbol: \_ZN7QwtPlot11eventFilterEP7QObjectP6QEvent

> > > Done (return code 1)

The machine I’m on is a gentoo box with gnuradio compiled as follows  
(notice qt4 is specified):

# emerge -pv gnuradio

These are the packages that would be merged, in order:

Calculating dependencies… done!  
[ebuild R] net-wireless/gnuradio-3.7.6.1:0/3.7.6.1::gentoo  
USE=“alsa analog audio ctrlport digital doc examples fcd filter grc jack  
oss qt4 sdl utils wavelet wxwidgets -atsc -channels -dtv -fec -log -noaa  
-pager -performance-counters -portaudio {-test} -trellis -uhd -vocoder  
-zeromq” PYTHON\_TARGETS=“python2\_7” 0 KiB

Total: 1 package (1 reinstall), Size of downloads: 0 KiB

As I mentioned, all works well with RTL-SDR source, so I assume there is  
a QT problem of some sort?

Thanks!  
Mike M.

---

<div class="post-metadata">

**Author:** ![mike-moscow](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/53a042/32.png) [@mike-moscow](https://www.ruby-forum.com/u/mike-moscow)\
**Post date:** [February 18, 2015, 10:29pm UTC](https://www.ruby-forum.com/t/newbie-problem/234252/2 "2015-02-18T22:29:34Z")

</div>

Just a followup to my own note. I did

ldd /usr/lib/libgnuradio-qtgui-3.7.6.1.so.0.0.0

and no library comes up as missing.

Thanks,  
Mike M.

---

<div class="post-metadata">

**Author:** ![mike-moscow](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/53a042/32.png) [@mike-moscow](https://www.ruby-forum.com/u/mike-moscow)\
**Post date:** [February 19, 2015, 12:22am UTC](https://www.ruby-forum.com/t/newbie-problem/234252/3 "2015-02-19T00:22:08Z")

</div>

Hey Mike,

If you suspect that you have problems with libraries, maybe you want to  
run  
the install script with the prereqs option to install all the  
dependencies.

wget [http://www.sbrac.org/files/build-gnuradio](http://www.sbrac.org/files/build-gnuradio) && chmod a+x  
./build-gnuradio && ./build-gnuradio prereqs

Thanks,  
Murray

---

<div class="post-metadata">

**Author:** ![mike-moscow](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/53a042/32.png) [@mike-moscow](https://www.ruby-forum.com/u/mike-moscow)\
**Post date:** [February 19, 2015, 2:10pm UTC](https://www.ruby-forum.com/t/newbie-problem/234252/4 "2015-02-19T14:10:15Z")

</div>

Murray, thanks for your idea which I’ll use if I need to avoid the  
gentoo “emerge” utility.

Rick, thanks, Bug 540658 was just posted. I hope the problem is simple  
to solve - and also not a blunder on my end. 🙂

Thanks, guys!  
Mike

On 02/18/2015 10:47 PM, Rick F. wrote:

> Thanks,  
> Zero\_Chaos
> 
> On 02/18/15 16:13, Mike M. wrote:  
> […] ‘Generate’ goes fine, but not ‘Execute’:
> 
> > ```
> > from qtgui_swig import *
> > 
> > ```
> > 
> > File “/usr/lib/python2.7/site-packages/gnuradio/qtgui/qtgui\_swig.py”,  
> > line 28, in   
> > \_qtgui\_swig = swig\_import\_helper()  
> > File “/usr/lib/python2.7/site-packages/gnuradio/qtgui/qtgui\_swig.py”,  
> > line 24, in swig\_import\_helper  
> > \_mod = imp.load\_module(‘\_qtgui\_swig’, fp, pathname, description)  
> > ImportError: /usr/lib/libgnuradio-qtgui-3.7.6.1.so.0.0.0: undefined  
> > symbol: \_ZN7QwtPlot11eventFilterEP7QObjectP6QEvent
> > 
> > > > > Done (return code 1)  
> > > > > […]

---

<div class="post-metadata">

**Author:** ![mike-moscow](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/53a042/32.png) [@mike-moscow](https://www.ruby-forum.com/u/mike-moscow)\
**Post date:** [February 19, 2015, 4:49am UTC](https://www.ruby-forum.com/t/newbie-problem/234252/5 "2015-02-19T04:49:09Z")

</div>

Mike,

I am the maintainer of Gnuradio in gentoo. Please open a gentoo bug at  
[https://bugs.gentoo.org](https://bugs.gentoo.org) with “emerge --info” as well as the full  
build.log for gnuradio (you will probably need to xz compress it)  
attached to the bug. We can help you fix the problem and get it fixed  
for all users. For what it’s worth, we saw a very similar issue several  
version ago and the problem turned out to be very obvious in the full  
build log. Likely there are some improper paths for QT getting  
autodetected.

Thanks,  
Zero\_Chaos

---

<div class="post-metadata">

**Author:** ![mike-moscow](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/53a042/32.png) [@mike-moscow](https://www.ruby-forum.com/u/mike-moscow)\
**Post date:** [February 21, 2015, 5:23am UTC](https://www.ruby-forum.com/t/newbie-problem/234252/6 "2015-02-21T05:23:53Z")

</div>

Just so the mailing list doesn’t feel out of the loop and the archives  
have the solution:

We successfully tracked this issue to resolution here:

[https://bugs.gentoo.org/show\_bug.cgi?id=540658](https://bugs.gentoo.org/show_bug.cgi?id=540658)

and merged the fix into gnuradio here:

> <https://github.com/gnuradio/gnuradio/pull/387/>
>
> allow finding qwt6-qt4 library. Some distros have added support for both qt4 an…d qt5 in qwt6, the common name the library uses appears to be qwt6-qt4. The pre-existance of the qwt-qt4 entry suggests this naming convention is reasonably standard (or at least this isn't a unique hack)

Thanks,  
Zero\_Chaos