Re: [Discuss-gnuradio] Error while receiving

[kaleem ahmad]

Hi Eric,

I am trying to use gdb and I found some other posts by you in which you
recomended that the pid should be printed in the begining and then wait for
an Enter to be pressed and before pressing Enter open a new terminal and
attach the pid of program_to_be_backtraced with gdb, I did it in the
following way:

#gdb bt pid

after this command gdb execute a sequence of commands ...loading...reading
which ends with the following:
................................
........................................
Loaded symbols for /usr/lib/libglib-2.0.so.0
Reading symbols from /usr/lib/libXinerama.so.1...
---Type <return> to continue, or q <return> to quit---  

when I pressed Enter at this point it again run similar loading and
reading...commands and ends at following:

Reading symbols from /usr/lib/libasound.so.2...done.
Loaded symbols for /usr/lib/libasound.so.2
Reading symbols from /usr/local/lib/libgr_audio_alsa.so.0...done.
Loaded symbols for /usr/local/lib/libgr_audio_alsa.so.0

0xffffe410 in __kernel_vsyscall ()
(gdb)

at this point I suppose I can enter bt command to print the
backtrace...........BUT the problem is the program which I want to get the
backtrace of , dont proceed...I mean as soon as it is attached to the gdb it
stops and never proceed untill I Enter 'q' in gdb window and then it asks me
the following:

(gdb) q
The program is running.  Quit anyway (and detach it)? (y or n)   
I say yes...and it terminates gdb AND in other terminal where my actual
program is running I receive a message:
 fusb::_reap: Interrupted system call......and after this my program
continues.

So my problem is... if my program will never run untill it is attached with
gdb how can I get backtrace and if I try to print backtrace when the program
is already crashed then its impossible....So please guide me if I am doing
something wrong? and suggest me how can I proceed?

Best Regards

Kaleem Ahmad


Eric Blossom wrote:
> 
> On Thu, Oct 09, 2008 at 07:29:51AM -0700, kaleem ahmad wrote:
>> 
>> Hi,
>> 
>> I am using USRP+RFX1400+SUSI
>> 
>> I am using following flow graph to receive data>
>> 
>> usrp_source_c -> gr.fir_filter_ccf -> gr.quadrature_demod_cf ->
>> gr.simple_correlator -> gr.vector_sink_b
>> 
>> Some time I receive following error:
>> 
>> *** glibc detected *** python: free(): invalid next size (fast):
>> 0x08fcd970
>> ***
>> Segmentation fault
>> 
>> Can you suggest what can be the problem and what can I do to solve it.
>> 
>> Thanks
>> Kaleem Ahmad
> 
> Not sure where it's actually blowing up (definitely a bug somewhere).
> A stack trace from gdb would provide clues.
> 
> However, the flow graph you give above is doomed to fail.  It will
> sooner or later exhaust all memory on your system.  When this happens
> is should fail gracefully, but it may not.
> 
> Eric
> 
> 
> _______________________________________________
> Discuss-gnuradio mailing list
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> 
> 

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