X Toolkit: heap is growing when recreating widgets - c

Question

I'm trying to understand why the following program is leaking memory. When I look at the heap size by using the command more /proc/<pid>/smaps, I can see that the heap is only growing. It seems that the XtDestroyWidget is not really freeing up the memory. I would be very grateful if somebody can tell me why this is happening and show me the right way of recreating widgets.
Thanks in advance!
/* Compile on Solaris: cc widgets_mem.c -lXm -lXt -lX11 */
/* Compile on Linux: gcc -m32 widgets_mem.c -lXm -lXt -lX11 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/keysymdef.h>
#include <Xm/MainW.h>
#include <Xm/PushB.h>
#include <Xm/Form.h>
Widget toplevel;
Widget w_main;
Widget w_bb;
Widget w_button = NULL;
Window root_win;
XtAppContext app;
int screen_number;
Display *display = NULL;
void recreateWidgets ()
{
printf ("recreating widgets\n");
XtDestroyWidget (w_button);
w_button = XtVaCreateManagedWidget (
"button",
xmPushButtonWidgetClass, w_bb,
XmNfillOnArm, False,
XmNhighlightThickness, 0,
XmNborderWidth, 1,
XmNmarginTop, 1,
XmNmarginWidth, 2,
XmNmarginHeight, 0,
XmNwidth, 20,
XmNheight, 10,
XmNrecomputeSize, False,
XmNalignment, XmALIGNMENT_CENTER,
NULL);
}
void main (int argc, char **argv)
{
XEvent event;
toplevel = XtVaAppInitialize (&app, "Mem leak test",
NULL, 0, &argc, argv, NULL, NULL);
display = XtDisplay (toplevel);
screen_number = DefaultScreen (display);
root_win = RootWindow (display, screen_number);
w_main = XtVaCreatePopupShell (
"main",
topLevelShellWidgetClass, toplevel,
XmNgeometry, "-0+0",
XmNborderWidth, 0,
XmNshadowThickness, 0,
XmNminWidth, 1,
XmNmwmDecorations, 0,
XmNmwmFunctions, 0,
XmNwidth, 600,
XmNheight, 200,
NULL);
w_bb = XtVaCreateManagedWidget (
"",
xmBulletinBoardWidgetClass, w_main,
XmNborderWidth, 4,
XmNshadowThickness, 0,
XmNmarginWidth, 0,
XmNmarginHeight, 0,
XmNx, 0,
XmNy, 0,
XmNwidth, 500,
XmNheight, 100,
NULL);
w_button = XtVaCreateManagedWidget (
"button",
xmPushButtonWidgetClass, w_bb,
XmNfillOnArm, False,
XmNhighlightThickness, 0,
XmNborderWidth, 1,
XmNmarginTop, 1,
XmNmarginWidth, 2,
XmNmarginHeight, 0,
XmNwidth, 20,
XmNheight, 10,
XmNrecomputeSize, False,
XmNalignment, XmALIGNMENT_CENTER,
NULL);
XtPopup (w_main, XtGrabNone);
while (1)
{
XtAppNextEvent (app, &event);
if (event.type == ButtonPress)
{
printf ("Button pressed, recreating widgets\n");
recreateWidgets();
}
}
}

Answer 1

I found the bug in my code: I had to add a XtDispatchEvent(&event), which handles the deallocating of the widgets which are on the destory list, an internal list in Xt.