Date: Wed, 20 Apr 2005 19:23:32 +0300 From: Giorgos Keramidas <keramida@ceid.upatras.gr> To: Joseph Koshy <joseph.koshy@gmail.com> Cc: freebsd-standards@freebsd.org Subject: Re: Standard type for code pointers? Message-ID: <20050420162332.GB52948@orion.daedalusnetworks.priv> In-Reply-To: <84dead720504200910441b9108@mail.gmail.com> References: <84dead720504200541539f4c15@mail.gmail.com> <03f22a3c76ac440b97e2179761dfd6fa@xcllnt.net> <20050420155407.GA844@falcon.midgard.homeip.net> <84dead720504200910441b9108@mail.gmail.com>
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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.
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