How to compile this code implementing Xm on Ubuntu 64 bit using Netbeans?

Question

I am just new to X-Windows and trying to code that just calls simple MessageBox on Linux like Window's.

I am on Ubuntu 12.04LTS 64bit and installed Netbeans full version. I included "/usr/include/Xm" to this project, and for libs, I included "Motif" libs.

and following error occurs when I compile the code:

main.cpp:24:63: error: invalid conversion from ‘void (*)(Widget, XtPointer, XmPushButtonCallbackStruct*) {aka void (*)(_WidgetRec*, void*, XmPushButtonCallbackStruct*)}’ to ‘XtCallbackProc {aka void (*)(_WidgetRec*, void*, void*)}’ [-fpermissive]
/usr/include/X11/Intrinsic.h:1241:13: error:   initializing argument 3 of ‘void XtAddCallback(Widget, const char*, XtCallbackProc, XtPointer)’ [-fpermissive] 

I really do not understand this error, at least I have never seen syntax like, "aka void blah blah~~".

Can anyone please help me fix this compile error and, if possible, please explain me what this error message mean?

Here is original source code:

#include <Xm/Xm.h> 
#include <Xm/PushB.h>

/* Prototype Callback function */

void pushed_fn(Widget , XtPointer , 
               XmPushButtonCallbackStruct *);


main(int argc, char **argv) 

{   Widget top_wid, button;
    XtAppContext  app;

    top_wid = XtVaAppInitialize(&app, "Push", NULL, 0,
        &argc, argv, NULL, NULL);

    button = XmCreatePushButton(top_wid, "Push_me", NULL, 0);

    /* tell Xt to manage button */
                XtManageChild(button);

                /* attach fn to widget */
    XtAddCallback(button, XmNactivateCallback, pushed_fn, NULL);

    XtRealizeWidget(top_wid); /* display widget hierarchy */
    XtAppMainLoop(app); /* enter processing loop */ 

}

void pushed_fn(Widget w, XtPointer client_data, 
               XmPushButtonCallbackStruct *cbs) 
  {   
     printf("Don't Push Me!!\n");
  }

Answer 1

XtAddCallback expects an XtCallbackProc Your pushed_fn may be compatible, but it isn't an XtCallbackProc because it uses Xm types directly.

Been a while since I've done Motif, so I could be wrong, but the solution might be:

void pushed_fn(Widget w, XtPointer client, XtPointer cbsXt)
{
    XmPushButtonCallbackStruct *cbs = (XmPushButtonCallbackStruct*)cbsXt;
    ...
}