# Signal processing block, ImportError, undefined symbol

**URL:** <https://www.ruby-forum.com/t/signal-processing-block-importerror-undefined-symbol/207107>\
**Category:** GNU Radio\
**Created:** [May 18, 2011, 4:17pm UTC](https://www.ruby-forum.com/t/signal-processing-block-importerror-undefined-symbol/207107 "2011-05-18T16:17:58Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![luislavena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/0ea827/32.png) [@luislavena](https://www.ruby-forum.com/u/luislavena)\
**Post date:** [May 18, 2011, 4:17pm UTC](https://www.ruby-forum.com/t/signal-processing-block-importerror-undefined-symbol/207107/1 "2011-05-18T16:17:58Z")

</div>

Hi all

I created a new signal processing block. The examples “howto\_square\_ff”,  
“howto\_square2\_ff” work fine. If I use “sudo make” and “sudo make  
check” (with my new block included) I get an Error:  
“Traceback (most recent call last):  
File “./qa\_howto.py”, line 24, in   
import howto  
File “/home/hoim/gr-howto-write-a-block-3.0.2/src/lib/howto.py”, line  
24, in   
\_howto = swig\_import\_helper()  
File “/home/hoim/gr-howto-write-a-block-3.0.2/src/lib/howto.py”, line  
16, in swig\_import\_helper  
import \_howto  
ImportError:  
/home/hoim/gr-howto-write-a-block-3.0.2/src/lib/.libs/\_howto.so:  
undefined symbol: \_Z25howto\_make\_detect\_cut\_vccjjjj”

I saw in the Discuss-gnuradio a thread called “Help with Undefined  
Symbol error — undefined sy” with nearly the same problem, but in my  
case I have not found a incorrectly named “make” function.

Any idea? Any help will be appreciated

Thanks  
Michael

---

<div class="post-metadata">

**Author:** ![SSMichael\_HSSinSS\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/7feea3/32.png) [@SSMichael\_HSSinSS\_S](https://www.ruby-forum.com/u/SSMichael_HSSinSS_S)\
**Post date:** [May 18, 2011, 5:35pm UTC](https://www.ruby-forum.com/t/signal-processing-block-importerror-undefined-symbol/207107/2 "2011-05-18T17:35:16Z")

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On Wed, 2011-05-18 at 16:16 +0200, Michael Höin wrote:

> ```
> _howto = swig_import_helper()
> 
> ```
> 
> File “/home/hoim/gr-howto-write-a-block-3.0.2/src/lib/howto.py”, line  
> 16, in swig\_import\_helper  
> import \_howto  
> ImportError: /home/hoim/gr-howto-write-a-block-3.0.2/src/lib/.libs/\_howto.so:  
> undefined symbol: \_Z25howto\_make\_detect\_cut\_vccjjjj"
> 
> I saw in the Discuss-gnuradio a thread called “Help with Undefined  
> Symbol error — undefined sy” with nearly the same problem, but in my  
> case I have not found a incorrectly named “make” function.

make distclean  
grep “howto” \* -r

that will give you a list of the things you need to change. ignore the  
various Makefile.swig.gen, Makefile.in, etc.

–n