GTK+ Forums

ecntrk · Familiar Face Joined: 25 Oct 2009 Posts: 13

Hello everybody,

I'm having a strange memory problem.

In a small code of mine, I've created a struct of some GtkWidgets and then typedefed it. I am reallocing the memory into the typedefed variable.
I'm freeing it in my main function.

Attaching my code here :

Code: (Plaintext)

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#include<stdio.h>
#include<unistd.h>
#include<string.h>
#include<gtk/gtk.h>
#include<stdlib.h>

/*building data structures */

GtkWidget *motherbox, *temp;

typedef struct core{
GtkWidget *img,*label,*dirname,*coreVbox,*eventbox,*align,*outerVbox;
} *_icon ;

_icon icon=NULL, icon_t;

int icon_no=0;
/****************************/

/*Prototypes **************************************/

//void filecreator(char *);
void show_dir(char *, char *);
void butn_prsd(GtkWidget *, GdkEventButton *, gpointer );
void set_init_space(void);

/***************************************************/

int main (int argc, char *argv[]){

gtk_init(&argc,&argv);
set_init_space();
show_dir("/home/ecntrk","home");
gtk_main();
free(icon);

return 0;
}

void set_init_space(void){

GtkWidget *window, *scrlwindow;

window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_widget_set_size_request(GTK_WIDGET(window), 400,300);
gtk_window_set_title(GTK_WINDOW(window), "File Manager 1.1");
g_signal_connect(G_OBJECT(window), "delete_event", G_CALLBACK(gtk_main_quit), NULL);

scrlwindow = gtk_scrolled_window_new(NULL, NULL);
gtk_scrolled_window_set_policy(GTK_SCROLLED_WINDOW(scrlwindow), GTK_POLICY_AUTOMATIC, GTK_POLICY_AUTOMATIC);

motherbox = gtk_hbox_new(FALSE,0);
gtk_scrolled_window_add_with_viewport(GTK_SCROLLED_WINDOW(scrlwindow), motherbox);
gtk_container_add(GTK_CONTAINER(window), scrlwindow);

temp = motherbox;
gtk_widget_show_all(window);

}

void show_dir(char *dname, char *labell){

icon = (_icon)realloc(icon, (++icon_no * sizeof(_icon)) );
icon_t=(_icon)(icon + icon_no -1);

/*creating core Vbox with icon image and label*/

icon_t->coreVbox = gtk_vbox_new(FALSE,0);
icon_t->label = gtk_label_new(labell);
icon_t->img = gtk_image_new_from_file("/home/ecntrk/folder.png");
icon_t->dirname = gtk_label_new(dname);//printf("tmp ptr %p butn_n0 %d\n",&temp, butn_no);

/*Packing !**************/
gtk_box_pack_start(GTK_BOX(icon_t->coreVbox), icon_t->img, FALSE, FALSE, 0);
gtk_box_pack_start(GTK_BOX(icon_t->coreVbox), icon_t->label, FALSE, FALSE, 0);

/******************** ****************************/

/*eventbox *****************************************/
icon_t->eventbox = gtk_event_box_new();//printf("tmp ptr %p butn_n0 %d\n",&temp, butn_no);
gtk_container_add(GTK_CONTAINER(icon_t->eventbox), icon_t->coreVbox);
gtk_event_box_set_above_child(GTK_EVENT_BOX(icon_t->eventbox),TRUE);

gtk_widget_set_events (icon_t->eventbox, GDK_BUTTON_PRESS_MASK);

g_signal_connect (G_OBJECT (icon_t->eventbox), "button_press_event", G_CALLBACK (butn_prsd),(gpointer) icon_t->label);

/*****Alignment **************************************/
icon_t->align = gtk_alignment_new(.5,.5,0,0);
gtk_container_add(GTK_CONTAINER(icon_t->align), icon_t->eventbox);

icon_t->outerVbox = gtk_vbox_new(FALSE,0);//printf("tmp ptr %p butn_n0 %d\n",&temp, butn_no);

gtk_box_pack_start(GTK_BOX(icon_t->outerVbox),icon_t->align,FALSE,FALSE,0);

/*Icon package complete ! */

gtk_box_pack_start(GTK_BOX(temp),icon_t->outerVbox,FALSE,FALSE,0);

gtk_widget_show_all(icon_t->outerVbox);
}

void butn_prsd(GtkWidget *evntbx, GdkEventButton *event , gpointer labeltwo){

gchar *hu=(gchar *)gtk_label_get_text(GTK_LABEL(labeltwo));
g_print(" ** %s **",hu);

}

First of all after execution, it says

Code: (Plaintext)

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ecntrk@mithai-Dell:~$ ./expndr11

(expndr11:5387): GLib-GObject-CRITICAL **: g_object_new: assertion `G_TYPE_IS_OBJECT (object_type)' failed

(expndr11:5387): Gtk-CRITICAL **: gtk_box_pack: assertion `GTK_IS_BOX (box)' failed

(expndr11:5387): Gtk-CRITICAL **: gtk_box_pack: assertion `GTK_IS_WIDGET (child)' failed

(expndr11:5387): Gtk-CRITICAL **: gtk_widget_show_all: assertion `GTK_IS_WIDGET (widget)' failed

Here, the desired icon and the label is not appearing. (though it appeared in the first time i tried to run the program.) Only the blank window is there.

then upon closing it, gives the error

Code: (Plaintext)
1 2 3 4	* glibc detected * ./expndr11: free(): invalid next size (fast): 0x083f4cf0 ***

followed by a large memory backtrace.

Am I missing something there?

/* tadeboro, buddy, are you listning? :) */

tadeboro · Posted: Wed Jan 06, 2010 12:01 am Post subject:

Hello.

The problem you're experiencing is not directly GTK+ related. I'll do my best to explain the problem, but you should consult your preferred C language literature for more details.

The problem starts at _icon type definition. You define _icon like this:

Code: (C)
1 2 3 4	typedef struct core { /* Struct members here / } _icon;

To rephrase this in English: _icon is a pointer to a struct core.

This is all fine. But then we encounter line 72:

Code: (C)
1	icon = (_icon)realloc(icon, (++icon_no * sizeof(_icon)) );

And here things break, because you allocate insufficient amount of memory. And the culprit is the sizeof() operator. You want to allocate enough memory to hold another core struct, but what you're really doing is allocating just enough memory to hold pointer to a core struct. Proper way of memory allocation in this case would be:

Code: (C)
1	icon = (_icon)realloc(icon, (++icon_no * sizeof(struct core)) );

I'm not sure if I managed to explain this well enough, but hopefully, you'll manage to extract some information out of this post.

Tadej

ecntrk · Familiar Face Joined: 25 Oct 2009 Posts: 13

Hey, Thanks for the nice help. That was an eye opener.
Btw, I was also trying this with (sizeof(struct core *)) but that also gives the problem...
I ran some trial and error through my code and after deleting the free(icon) , My code ran without a hitch !!!
After some time, I added some more functions to it ( I created a separate file for it) then tried to run it again. Alas.. the memory corruption happened again !
From that on, my original code that ran at first, is not running as well.

This has totally boggled my mind !

Dunno what's the reason .. !

dreblen · Posted: Thu Jan 07, 2010 4:06 am Post subject:

I think that your problem is that you're still allocating the size of one pointer (in this case, sizeof(struct core *)).
This will allocate enough memory for one pointer (say, 4 bytes), but your struct has seven pointers and needs more memory (28 bytes).
To get the right amount of memory, you need to use sizeof(struct core) without the asterisk that's in your current code.

ecntrk · Familiar Face Joined: 25 Oct 2009 Posts: 13

Hey thanks for your nice help :)

yeah, exactly,
I realised that and my problem's gone.

Thank you very much for your time and nice support.