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From: diamond@diamond.csl.sony.junet (Norman Diamond)
Newsgroups: comp.lang.c
Subject: Re: function casting
Message-ID: <10206@socslgw.csl.sony.JUNET>
Date: 2 May 89 04:35:18 GMT
References: <12481@umn-cs.CS.UMN.EDU> <9266@alice.UUCP>
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Reply-To: diamond@csl.sony.junet (Norman Diamond)
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In article <12481@umn-cs.CS.UMN.EDU>, clark@umn-cs.CS.UMN.EDU (Robert P. Clark) writes:

>> How do I cast something to a pointer to a function that returns
>> an integer?

In article <9266@alice.UUCP> ark@alice.UUCP (Andrew Koenig) writes:

>Best would be to make foo return an appropriate pointer ane
>avoid type cheating:
>
>	int (*foo())();
>	int (*f)();
>
>	f = foo();
>
>The declaration of foo here says that if you call foo, dereference the
>result, and call that, you get an int.  The definition of foo would
>look something like this:
>
>	int (*foo())()
>	{
>		/* ... */
>	}
>
>Don't be too astonished if your compiler balks at this -- but
>it is indeed valid C.

Mr. Koenig's answers are 100% correct.  However, the use of typedef
might solve the problem of broken compilers, and maybe even the
problem of broken co-workers who have to read your code:

typedef int                   purpose_of_f_t();
typedef purpose_of_f_t       *purpose_of_f_ptr_t;
typedef purpose_of_f_ptr_t    purpose_of_foo_t();

purpose_of_foo_t              foo;
purpose_of_f_ptr_t            f_ptr;
int                           my_int;

    /* ... */
    f_ptr = foo();
    /* ... */
    my_int = (*f_ptr)();

purpose_of_foo_t foo()
{
    /* ... */
}


Norman Diamond, Sony Computer Science Lab (diamond%csl.sony.jp@relay.cs.net)
  The above opinions are my own.   |  Why are programmers criticized for
  If they're also your opinions,   |  re-inventing the wheel, when car
  you're infringing my copyright.  |  manufacturers are praised for it?