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Date: Wed, 20 Apr 2005 19:23:32 +0300
From: Giorgos Keramidas <keramida@ceid.upatras.gr>
To: Joseph Koshy <joseph.koshy@gmail.com>
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cc: freebsd-standards@freebsd.org
Subject: Re: Standard type for code pointers?
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On 2005-04-20 16:10, Joseph Koshy <joseph.koshy@gmail.com> wrote:
>> Except that intptr_t need only be large enough to hold an object
>> pointer.  This is not necessarily enough to hold a function pointer.
>
> Right.
>
>> The only standard types that are guaranteed to be able to hold a
>> function pointer are other function pointers.
>
> Right, but there doesn't seem to be a C99 name for function
> pointer types.

There is no need for an explicit typedef.  If you do know the type of
the function pointed at by a function pointer, you can declare the
pointer using the correct type:

	char prog_name[] = "/bin/sh";
	char *args[] = { prog_name };
	int (*fptr)(int, char **);

	fptr = main;
	fptr(1, args);

> Is 'register_t' guaranteed to be wide enough?

AFAIK, no.  Portable C code cannot assume that a function pointer is
small enough to fit in a single machine register.  Some obscure
architecture may choose to represent function entry points with as
many register as it needs.