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From: alex@hpgnd.grenoble.hp.com (Alexis MERMET-GRANDFILLES)
Newsgroups: comp.lang.c
Subject: ANSI C and typedef of function types
Message-ID: <340001@hpgnd.grenoble.hp.com>
Date: 28 Jun 91 12:19:03 GMT
Organization: Hewlett-Packard, GND
Lines: 48

Hello,

X11/Instrinsic.h defines the type "XtEventHandler" as :
=>  typedef void (*XtEventHandler)(Widget, XtPointer, XEvent *,Boolean *);


Let's imagine now that I want to create a new Event Handler called foo.

The routine XtAddEventHandler registers the new event handler :

=> XtAddEventHandler( Widget w, EventMask event_mask, Boolean nonmaskable,
                      XtEventHandler foo, XtPointer client_data) ;

So foo needs to be of type XtEventHandler. Therefore I had in my header file :

foo.h:
=> XtEventHandler foo;

And the definition of the foo routine occurs in the source module:

foo.c:
=> #include "foo.h"
   void foo (Widget w, XtPointer data, XEvent *event, Boolean *cont)
   {
	...
   }


The ANSI compiler then claims the type of foo is incompatible with the
declaration.

I tryied to declare foo in the header file as :
void foo(Widget, XtPointer, XEvent *,Boolean *);

Then the compiler claimed , when calling the XtAddEventHandler , that
the foo parameter is of a wrong type ( void(*)() instead of XtEventHandler ).


So, What am I missing ?

Any help will be very appreciated.

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Alexis MERMET-GRANDFILLES             HEWLETT-PACKARD
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