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| From | Nobody <nobody@nowhere.com> |
|---|---|
| Subject | Re: Address of array && address of pointer to array |
| Date | 2011-09-16 13:09 +0100 |
| Message-Id | <pan.2011.09.16.12.09.53.574000@nowhere.com> |
| Newsgroups | comp.lang.c |
| References | (2 earlier) <70593967-7007-4f11-8cc6-299130de8451@24g2000yqr.googlegroups.com> <0.e3a2ad104ce357e0d1d6.20110915105419BST.87aaa6yvuc.fsf@bsb.me.uk> <3d340062-c7f4-46d8-8cce-0984d6db9096@v18g2000yqj.googlegroups.com> <pan.2011.09.15.13.48.15.666000@nowhere.com> <lnzki590lx.fsf@nuthaus.mib.org> |
| Organization | Zen Internet |
On Thu, 15 Sep 2011 10:28:10 -0700, Keith Thompson wrote:
>> An
>> implementation is free to print e.g. "?" for every pointer.
>
> No, it isn't. The string printed by printf with "%p" must be readable
> by scanf with "%p", and the result from scanf must compare equal to the
> original pointer.
Ah. I actually checked the spec regarding printf("%p"), which doesn't say
anything useful:
p The argument shall be a pointer to void. The value
of the pointer is converted to a sequence of
printable characters, in an implementation-defined
manner.
It didn't occur to me to check scanf(), which says:
p Matches an implementation-defined set of sequences,
which should be the same as the set of sequences
that may be produced by the %p conversion of the
fprintf function. The corresponding argument shall
be a pointer to a pointer to void. The
interpretation of the input item is implementation-
defined. If the input item is a value converted
earlier during the same program execution, the
pointer that results shall compare equal to that
value; otherwise the behavior of the %p conversion
is undefined.
Which suggests that the answer to the question:
> Can we say that, two pointers must be equal if they are printed the same.
should be "yes" (subject to the proviso that comparing the pointers for
equality is actually legal).
However: I suggest that it would be legal for the implementation to print
all pointers as "?" if it can detect that the *scanf() functions aren't
used by the program.
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Address of array && address of pointer to array Stanley Rice <heconghui@gmail.com> - 2011-09-14 06:12 -0700
Re: Address of array && address of pointer to array Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-14 14:41 +0100
Re: Address of array && address of pointer to array Paul N <gw7rib@aol.com> - 2011-09-14 14:15 -0700
Re: Address of array && address of pointer to array Peter Nilsson <airia@acay.com.au> - 2011-09-14 19:25 -0700
Re: Address of array && address of pointer to array Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-15 10:54 +0100
Re: Address of array && address of pointer to array Stanley Rice <heconghui@gmail.com> - 2011-09-15 05:36 -0700
Re: Address of array && address of pointer to array Ike Naar <ike@sverige.freeshell.org> - 2011-09-15 13:46 +0000
Re: Address of array && address of pointer to array Nobody <nobody@nowhere.com> - 2011-09-15 14:48 +0100
Re: Address of array && address of pointer to array Keith Thompson <kst-u@mib.org> - 2011-09-15 10:28 -0700
Re: Address of array && address of pointer to array Stanley Rice <heconghui@gmail.com> - 2011-09-15 18:23 -0700
Re: Address of array && address of pointer to array Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-16 12:58 +0100
Re: Address of array && address of pointer to array James Kuyper <jameskuyper@verizon.net> - 2011-09-16 08:03 -0400
Re: Address of array && address of pointer to array Nobody <nobody@nowhere.com> - 2011-09-16 13:09 +0100
Re: Address of array && address of pointer to array Keith Thompson <kst-u@mib.org> - 2011-09-16 12:05 -0700
Re: Address of array && address of pointer to array gazelle@shell.xmission.com (Kenny McCormack) - 2011-09-16 19:35 +0000
Re: Address of array && address of pointer to array Peter Nilsson <airia@acay.com.au> - 2011-09-19 15:45 -0700
Re: Address of array && address of pointer to array Keith Thompson <kst-u@mib.org> - 2011-09-19 17:47 -0700
Re: Address of array && address of pointer to array James Kuyper <jameskuyper@verizon.net> - 2011-09-15 10:21 -0400
Re: Address of array && address of pointer to array Stanley Rice <heconghui@gmail.com> - 2011-09-15 05:22 -0700
Re: Address of array && address of pointer to array James Kuyper <jameskuyper@verizon.net> - 2011-09-15 10:23 -0400
Re: Address of array && address of pointer to array pete <pfiland@mindspring.com> - 2011-09-15 15:26 -0400
Re: Address of array && address of pointer to array Stanley Rice <heconghui@gmail.com> - 2011-09-15 18:14 -0700
Re: Address of array && address of pointer to array Keith Thompson <kst-u@mib.org> - 2011-09-16 02:09 -0700
Re: Address of array && address of pointer to array James Kuyper <jameskuyper@verizon.net> - 2011-09-16 08:39 -0400
Re: Address of array && address of pointer to array pete <pfiland@mindspring.com> - 2011-09-16 18:08 -0400
Re: Address of array && address of pointer to array Bart van Ingen Schenau <bart@ingen.ddns.info> - 2011-09-16 16:38 +0200
Re: Address of array && address of pointer to array cri@tiac.net (Richard Harter) - 2011-09-16 22:04 +0000
Re: Address of array && address of pointer to array Stanley Rice <heconghui@gmail.com> - 2011-09-15 18:08 -0700
Re: Address of array && address of pointer to array Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-16 13:12 +0100
Re: Address of array && address of pointer to array James Kuyper <jameskuyper@verizon.net> - 2011-09-16 08:30 -0400
Re: Address of array && address of pointer to array Keith Thompson <kst-u@mib.org> - 2011-09-15 11:51 -0700
Re: Address of array && address of pointer to array Stanley Rice <heconghui@gmail.com> - 2011-09-15 18:13 -0700
Re: Address of array && address of pointer to array James Kuyper <jameskuyper@verizon.net> - 2011-09-15 21:18 -0400
Re: Address of array && address of pointer to array Stanley Rice <heconghui@gmail.com> - 2011-09-16 05:37 -0700
Re: Address of array && address of pointer to array James Kuyper <jameskuyper@verizon.net> - 2011-09-16 09:46 -0400
Re: Address of array && address of pointer to array Keith Thompson <kst-u@mib.org> - 2011-09-16 12:08 -0700
Re: Address of array && address of pointer to array Nobody <nobody@nowhere.com> - 2011-09-16 13:20 +0100
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