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From: kremer@cs.odu.edu (Lloyd Kremer)
Newsgroups: comp.lang.c
Subject: Re: pointers to pointers to functions
Summary: The compiler is not too smart.
Message-ID: <10174@xanth.cs.odu.edu>
Date: 12 Oct 89 18:13:11 GMT
References: <8247@medusa.cs.purdue.edu>
Distribution: usa
Organization: Old Dominion University, Norfolk, Va.
Lines: 61



In article <8247@medusa.cs.purdue.edu> bouma@cs.purdue.EDU (William J. Bouma)   writes:

>    I need a list of pointers to functions to be malloced. What is
>    the syntax? I declared this thing to hold it:
>
>         int (**f)();
>
>    And then I tried mallocing some space for it like this:
>
>         f = (int (**)()) malloc(n * sizof(*f));
>
>    When the compiler hits that line I get this:
>
>        illegal lhs of assignment operator
>        unacceptable operand of &
>        warning: illegal pointer/integer combination, op =
>        cannot recover from earlier errors: goodbye!


There is nothing wrong with this code (other than the misspelling of sizeof).
Some compilers have trouble with complicated double indirection.  They're
broken; what can I say?  Sometimes they need a little help in the form of
a simplifying typedef, such as:

	typedef int (*PFI)();  /* Pointer to Function returning Int */

	PFI *f;  /* pointer to a PFI */

	f = (PFI *)malloc(n * sizeof(*f));

Some programmers are helped by this nomenclature also.  :-)


>    Also, C doesn't care if I call the function:
>
>        (*f[x])();
>
>   or
>
>        (f[x])();

Right, it doesn't.  I prefer the first form since it reminds the reader
that programmer-defined function pointers are in use.  One must remember
that a function name without its argument list is taken as a pointer to
the function.  Hence a simple function call like

	printf("Hello, world\n");

is, syntactically, a pointer to a function followed by a parenthesized
argument list.  It is syntactically equivalent to

	(*printf)("Hello, world\n");

and should compile to exactly the same thing.

-- 
					Lloyd Kremer
					...!uunet!xanth!kremer
					Have terminal...will hack!