Re: pointer casts

[James Henstridge <james daa com au>]

Owen Taylor wrote:

> Miroslaw Dobrzanski-Neumann <mne mosaic-ag com> writes:
>
> > Hi,
> >
> > Compiling gclosure.c with DEC C V5.6-082 compiler I get the warnings listed
> > below (the same warnings are produced by the ibm xlc compiler). The problem is
> > that pointer to void is not the same as pointer to function. You can safe cast
> > data pointer but casting function pointer in i.e. pascal calling convention and
> > calling it afterwards as different ones produce a desaster.
> >
> > After having take a look at the data types of the two sides of the assignemt I
> > wonder how it works.
> >
> > gclosure.c:107 closure->marshal = (gpointer) ndata->notify;
>
> GCC has a non-standard extension that allows implicit casts betweeen (void *)
> and any function pointers.
>
> Unfortunately, this has led to people doing bad stuff like this and also to
> some messed up prototypes like:
>
> gulong	 g_signal_handler_find		      (gpointer		  instance,
> 					       GSignalMatchType	  mask,
> 					       guint		  signal_id,
> 					       GQuark		  detail,
> 					       GClosure		 *closure,
> 					       gpointer		  func,
> 					       gpointer		  data);
>
> That we just have to live with at this point.
>
> I've given Erwann the go ahead to commit his patch in #73898 which should fix
> all of these sorts of warnings in GLib.
Would GCC's -Wbad-function-cast warning flag warn about these sort of 
bad casts?

James.

--
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