Thread: Pointer confused... :-(

Hello all,

I have a problem with some pointers. I am very new to C ...

I have a function "open_project_file", this function initializes a struct called ZConf. open_project_file should now call an external function whicht should read the project data from XML and asign the content to my struct.

Here is my dummy code:

Code:

typedef struct _ZConf {
    gchar *projectname;
    gchar *projectpath;
} ZConf;

int open_project_file() {
    ZConf settings;
    read_xml(&settings);

    /* this line does not work 
   !!!! i don't can access the data in the structure!!!!*/
    printf(settings.projectname);
    printf(settings.projectpath);
}

void read_xml(ZConf *settings) {
    /* does some file integrity checks */
    /* then calls: */
    parse_xml(settings);
}

void parse_xml(ZConf *settings) {
    /*parse the XML file and insert values to the structure */
    settings->projectname = "Damn_pointers";
    settings->projectpath = "/home/hanez/projects";
}

Sorry, when not described perfect but the original code is much more complex and i don't want to post all the files. I think you could the understand the problem anyway... I know you can because you know how to hack in C... :-)

I would be very glad if someone could help me out.

Kind regards,
Johannes - hanez.org

Originally Posted by hanez

Hello all,

I have a problem with some pointers. I am very new to C ...

S the original code is much more complex and i don't want to post all the files

Well, there is nothing wrong with the functions you posted, except you forgot to give a return value in open_project_file().

Breaking the project down into a minimal set of functions that exhibits the problem is a pretty good path to debugging, however...


If you compile and execute just the lines that you posted (and a typedef for gchar and a main() that invokes open_project_file()), what do you get? I get the expected printout.

If these functions don't give you the expected printout in open_project_file(), then put printf statements in the other functions to see where it gets broken.

Regards,

Dave

What's a gchar? It had better be the same thing as a char, or this call to printf isn't going to work. Also, you usually want to not just pass something as the first argument to printf that isn't a specifically set control string. Otherwise, the user could fill 'projectname' with a string which has embedded % specifiers and printf would be expecting more to follow just the single argument.

Thanks for reply!

I am using Glib from the GNOME project and a gchar is wrapped char. It is the same type. Sorry for my fault in printf. I know the format method of strings but forgot to write them teh right way in my example. Sorry!

My mainproblem is, that i don't can access the data in the structure. I am reading the code at the monet and i will follow up with more information when i know. Maybe i will post the original code but there are many files and i don't want to do that here. I will write a better example that not works on my machine anyway when i don't find the error within the next hour...

Regards,
Johannes

Hello,

thanks to all of you. It helped me thinking in another way.

I am very new to C and this was my first post. Sorry for the dump question. The code i originally posted is running with the elementary fixes on my system. My problem was, that i had many more files with many things that are done before making use of the vars in the struct. Anywhere in this construct of functions i have made a free command in the XML parser and this free comand has deleted the content of my pointers in the struct.

Just, you know my fault now.

Sorry again and thanks! I will come back again with better declared problems... ;-)

Have a nice day...
Johannes