Re: Lost Pointer when adding GTK+ to an application

[James Scott Jr <skoona verizon net>]

On Wed, 2008-05-07 at 21:02 -0600, Diego Rivera wrote:
> Thanks for the quick answer, however, the GTK+ component is the same
> process as the Console application. The console application checks for
> some arguments and finishes by calling the working function of the
> application with parameters that reflect the arguments received from
> the console. My GtkButton callback just calls this last function with
> some parameters i have selected. 
> 
> So no inter-process communication is requiered
> 
> Thanks for the suggestion anyway
> 
OK, then you need to post some relevant portion of the code if possible.
These type of issues can be as casued by simple things like - using
local stack memory for structures vs malloc or g_new0() memory for them.

Post your main() and the callback for us to look at.  And please do
consider the valgrind suggestion, or retry the gdb exercise.

James,

> -Diego--
> 
> On Wed, May 7, 2008 at 8:55 PM, James Scott Jr <skoona verizon net>
> wrote:
>         
>         
>         
>         On Wed, 2008-05-07 at 20:33 -0600, Diego Rivera wrote:
>         > Hi! I am not exactly new to GTK+, however I have come across
>         a problem i
>         > have no explanation for, and I'll be glad if someone could
>         point me towards
>         > a possible solution.
>         >
>         > I am currently developing an application that uses various
>         algorithms for
>         > sequence alignment in biological applications (DNA, RNA,
>         Proteins and so
>         > on). This application is mainly for scientific purposes.
>         >
>         > The core algorithms are already running fine as a console
>         application in a
>         > very stable version. I am working in adding some graphical
>         interface to the
>         > program using GTK+. So, I built a little Window that asks
>         for the different
>         > parameters and makes a call to the already defined functions
>         in the console
>         > application, which are indeed stable. However, when making
>         the call to the
>         > algorithm with GTK+ running, some of the pointers in my data
>         structures get
>         > lost, and I just get a Segmentation Fault.
>         >
>         > While trying to debug this weird behavior, I have narrowed
>         the problem to
>         > the fact of having a window running.
>         >
>         > Right now, I just have a main that creates a GtkWindow with
>         a GtkButton, and
>         > the callback of the button calls the stable routine of the
>         console
>         > application using some "hard-wired" parameters. I have made
>         tests and the
>         > console application gives the correct answer for those
>         parameters. However,
>         > when calling the routine from the callback, Segmentation
>         Fault is the only
>         > result I have been able to get.
>         >
>         > I have tried with different versions of GTK+ and the outcome
>         is persistent.
>         >
>         > The data structure of the console application looks
>         something like this:
>         >
>         > typedef struct{
>         >     int length;
>         >     char* seq;
>         > }sequence_t;
>         >
>         > typedef struct{
>         >     int n;
>         >     int m;
>         >     int** table;
>         > }table_t;
>         >
>         > typedef struct{
>         >     sequence_t* vp;
>         >     sequence_t* wp;
>         >     table_t* table;
>         >     int scoring;
>         >     int result;
>         > }alignment_t;
>         >
>         > Using gdb i have found that the Segmentation Fault occurs at
>         some point when
>         > accesing the table from the alignment.
>         >
>         > I believe i have made no memory errors in my console
>         application, since it
>         > runs ok every time. However, i haven't seen the correct
>         output from my GTK
>         > application.
>         >
>         > Is there any hint that you could give me in order to correct
>         the error?
>         >
>         
>         How did you add the GTK component to the existing console app;
>         are they
>         one process or two?
>         
>         Your segfault suggest that they are two separate processes.
>          In which
>         case attempting to share memory elements will cause a segfault
>         every
>         time no matter how correct and hard-coded the structures.
>         
>         You may need to consider designing in and using some type of
>         IPC
>         (Inter-Process Communications) like a named-pipe,
>         shared-memory, socket
>         communications, memory queue, etc.  Something designed to
>         communicate
>         between two active processes.
>         
>         James,
>         
>         
>         > Thanks
>         > - Diego Rivera -
>         > _______________________________________________
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>         
>         
>