Date: Sun, 23 Sep 2001 20:45:14 +0200 From: Erik Trulsson <ertr1013@student.uu.se> To: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/usr.sbin/sysinstall command.c config.c Message-ID: <20010923204513.A48432@student.uu.se> In-Reply-To: <200109231749.NAA01962@glatton.cnchost.com> References: <20010923180124.I13390-100000@delplex.bde.org> <200109231749.NAA01962@glatton.cnchost.com>
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On Sun, Sep 23, 2001 at 10:49:28AM -0700, Bakul Shah wrote:
> > > Use '%p' when printing out the address of a function.
> > > sizeof(int) != sizeof(long)
> >
> > %p is for printing pointers of type "void *". It is unsuitable for
> > printing arbitrary pointers to objects. It is especially unsuitable
> > for printing pointers to functions.
>
> I have an old (1997) working draft of C9X which says
>
> 6.2.2.3 Pointers
>
> [#1] A pointer to void may be converted to or from a pointer
> to any incomplete or object type. A pointer to any
> incomplete or object type may be converted to a pointer to
> void and back again; the result shall compare equal to the
> original pointer.
>
> Since any object ptr may be converted to %p, you can do, e.g.
>
> printf("...%p...", ..., (void*)&some_function, ...);
>
> But you seem to be saying this is not be a valid conversion.
> Have things changed since then or is a function not
> considered an "object"? I would appreciate a C standard
> reference ( i.e. chapter and verse!) that shows this is
> invalid.
In general function pointers cannot be converted to/from non-function
pointers.
Functions are indeed not considered objects.
In a somewhat more recent (Jan 1999) draft of C9X 'object' is defined
as follows:
3.15
[#1] object
region of data storage in the execution environment, the
contents of which can represent values
[#2] NOTE When referenced, an object may be interpreted as
having a particular type; see 6.3.2.1.
--
<Insert your favourite quote here.>
Erik Trulsson
ertr1013@student.uu.se
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