Re: g_list problem

[Tristan Van Berkom <vantr touchtunes com>]

if you want to modify the value of an "int"
in a function call; you have to pass the addresss
of your int. This goes for a ptr-to-GList aswell.

(I think standard C supports 8 levels
of abstraction i.e. "int function(GList ********list);")


solution A:
        GList *list = NULL;
        list = function(list);
                
GList *function(GList *list)
{
        GList *ret = list;
        ret = g_list_append(ret, "data");
        /* ... */
        return ret;
}


solution B:

        GList *list = NULL;
        function(&list);

int function(GList **list)
{
        *list = g_list_append(tmp, "data");
        /* ... */
        return 1;
}

Cheers,
        -Tristan


Jean-Max Redonnet wrote:
> Hello,
>
> I have a problem with allocation of first element in a GList. This GList
> should de declarated in the main function, but contents are computed into
> another function (included into another file). I've written a small program
> to illustrate my purpose :
>
> the secondary file is :
> #include <gtk/gtk.h>
>
> int function(GList *list)
> {
>         list = g_list_append(list, "First");
>         list = g_list_append(list, "Second");
>         list = g_list_append(list, "Third");
>
>         return 1;
> }
>
> and in the main file I put :
> #include <gtk/gtk.h>
>
> int main()
> {
>         GList *list = NULL;
>
>         function(list);
>         g_print("word is %s \n", (char *)list->data);
>
>         return 0;
> }
>
> This is, I guess, the traditional way to use GLists. But in this case, it's
> doesn't work. This is not surprising because a null pointer is passed to
> function() and a not null-pointer should be returned because of
> g_list_append().
>
> To workaround this problem I allocate un empty element before of calling
> function() and I remove this element after function(). Here is the code of
> main file (secondary file doesn't change) :
>
> #include <gtk/gtk.h>
>
> int main()
> {
>         GList *list = g_list_alloc();
>
>         function(list);
>         list = g_list_remove(list, g_list_nth_data(list, 0));
>         g_print("word is %s \n", (char *)list->data);
>
>         return 0;
> }
>
> This is working fine, but this solution isn't very elegant. Is there is
> another way to solve this problem ?
>
> Thanks for any help.
>
> --
> ______________________________________________________________________________
> Jean-Max Redonnet                        mailto:redonnetNOSP Mlgmt ups-tlse fr
> please replace NOSP M with @ for reply
> remplacez NOSP M par @ pour répondre
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