From 3574416490717901329 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,9684813612e15361 X-Google-Attributes: gidf78e5,public From: James Kuyper Subject: Re: pointers: sizeof(pointer) Date: 1998/06/23 Message-ID: <358E8276.446B@wizard.net>#1/1 X-Deja-AN: 365198225 Approved: Fergus Henderson Content-Transfer-Encoding: 7bit References: X-Original-Date: Mon, 22 Jun 1998 12:12:38 -0400 Content-Type: text/plain; charset=us-ascii Organization: NASA Goddard Space Flight Center -- Greenbelt, Maryland USA X-Auth: PGPMoose V1.1 PGP comp.std.c++ iQBFAgUANY8r5OEDnX0m9pzZAQHqagF/TTTS+yheI20jzMmShiKucDXbbL2w9XiJ mlTo49YIuufjFXQCMJQH2HKC/lbQUk+g =hX0x Mime-Version: 1.0 Newsgroups: comp.std.c++ Tony Cook has already answered most of this; I'll just add a few more points. Siemel Naran wrote: > > (1) > > [X] Do all pointers have the same size? This > makes sense because a pointer of any type is > just a memory addresss. It need not be just a memory address. If an implementation chooses to implement run-time array bounds checking, the necessary information may be included in the pointer. There are also a lot of different virtual memory schemes out there, some of which require complicated pointers. > [X] But what about inheritance where one pointer > can really be two pointers? For example, if > class D derives from class B, the a pointer to > a B can also possibly be a pointer to a D. It can be, but it needn't be. Casts within a class hierarchy can be highly non-trivial. > [X] The business of casting is just a compile > time check on the correctness of our code. > Correct? No. Among other things, casting a pointer to a new type will generally include changing its value, as needed, to match the alignment restrictions of the new type. > (2) Can we assume that sizeof(pointer)=sizeof(int)? No. In fact, there is no guarantee than any integer type is large enough to store a pointer; not even unsigned long. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://reality.sgi.com/austern_mti/std-c++/faq.html ]