Xref: utzoo comp.lang.c:11760 comp.lang.c++:1405
Path: utzoo!attcan!uunet!mcvax!philmds!leo
From: leo@philmds.UUCP (Leo de Wit)
Newsgroups: comp.lang.c,comp.lang.c++
Subject: Re: double pointer to function
Message-ID: <577@philmds.UUCP>
Date: 8 Aug 88 10:16:10 GMT
References: <107@cyclopes.UUCP>
Reply-To: leo@philmds.UUCP (Leo de Wit)
Organization: Philips I&E DTS Eindhoven
Lines: 45

In article <107@cyclopes.UUCP> stergios@athsys.UUCP (Stergios Marinopoulos) writes:
|Can anyone  figure  out why  the  following   code  does not   compile
|correctly?  The first ?/: pair makes cc (sun  3.4) complain, while the
|second one does not.  The only difference between the two is where the
|double pointer to functions  get  dereferenced.  Don't  think for    a

It is not the only difference. The second uses a cast for the second
operand (the one after :) so that the types of both parts of the ?:
expression are the same.

|second I write   code like this, it's  the  ouput of  a C++ translator
|considerably simplified and cleaned up.
|
|
|struct A { int (**A_tablePtr )(); } ;

   [stuff deleted]......

|void A_c (this , pmf )
|struct A *this ;
|void *pmf ;
|{
|
|  extern int flag ;
|
|  /* code ccxx produces and error message cc spits out */
|  /* warning: illegal pointer combination: illegal types in : */
|  (*(
|     (void (*)()) ( flag ?
|		   (*((void (**)())pmf ))
|		   :
|		   (this -> A_tablePtr [(((unsigned int )(*(((void (**)())pmf ))))) - 1])
|		   )
|     )
|   )
|    ( this ) ;

The type of the first part of the ?: expression is different from the type
of the second part (no, I don't want to spell it out 8-), so I think cc
is correct to complain (see also K&R 7.13 about the conditional operator).

In the second part (the 'hack') both parts are cast to (void (**)()) so
there is no problem here.

      Leo.