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| From | Anton Shepelev <anton.txt@gmail.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] |
| Date | 2016-11-22 23:23 +0300 |
| Organization | A noiseless patient Spider |
| Message-ID | <20161122232309.40aa1289366c35d048c594f3@gmail.com> (permalink) |
| References | <87oa1zgzw0.fsf@starless.ames.family> <20161121165927.aae89b9f861247b4a268e1bd@g{oogle}mail.com> <69c8a6e9-9685-6047-21fd-0721bcf899a1@verizon.net> |
James R. Kuyper to Anton Shepelev:
> > Am I right in thinking that "Object-oriented
> > programming in C":
> >
> > http://www.cs.rit.edu/~ats/books/ooc.pdf
> >
> > is based entirely on the violation of strict
> > aliasing?
>
> I don't have time to read that entire document
> right now. Could you cite a particular page that
> involves such violations? I know that the general
> concept of "object-oriented programming in C" (as
> opposed to the book of that title) does not rely
> violation of C's aliasing rules.
The author makes extensive use of casting between
non-aliasing pointers. He writes:
1. Passing a circle as a point means converting
from a struct Circle * to a struct Point *.
We will refer to this as an up-cast from a
subclass to a superclass -- in ANSI-C it can
only be accomplished with an explicit conver-
sion operator or through intermediate void *
values.
2. It is usually unsound, however, to pass a
point to a function intended for circles such
as Circle_draw(): converting from a struct
Point * to a struct Circle * is only permissi-
ble if the point originally was a circle. We
will refer to this as a down-cast from a su-
perclass to a subclass -- this requires ex-
plicit conversions or void * values, too, and
it can only be done to pointers to objects
that were in the subclass to begin with.
3. #define x(p) (((const struct Point *)(p)) -> x)
#define y(p) (((const struct Point *)(p)) -> y)
These macros can be applied to a pointer to
any object that starts with a struct Point,
i.e., to objects from any subclass of our
points. The technique is to up-cast the
pointer into our superclass and reference the
interesting component there. const in the
cast blocks assignments to the result. If
const were omitted
#define x(p) (((struct Point *)(p)) -> x)
a macro call x(p) produces an l-value which
can be the target of an assignment. A better
modification function would be the macro defi-
nition
#define set_x(p,v) (((struct Point *)(p)) -> x = (v))
which produces an assignment.
--
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Aliasing and subtyping structs Andreas <nospam@invalid.invalid> - 2016-11-01 13:15 +0100
Re: Aliasing and subtyping structs Andreas <nospam@invalid.invalid> - 2016-11-01 13:34 +0100
Re: Aliasing and subtyping structs Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-11-01 15:27 +0000
Re: Aliasing and subtyping structs Andreas <nospam@invalid.invalid> - 2016-11-02 09:47 +0100
Re: Aliasing and subtyping structs Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-11-02 15:47 +0000
Re: Aliasing and subtyping structs Andreas <nospam@invalid.invalid> - 2016-11-08 00:24 +0100
Re: Aliasing and subtyping structs supercat@casperkitty.com - 2016-11-07 21:42 -0800
Re: Aliasing and subtyping structs <william@wilbur.25thandClement.com> - 2016-11-03 18:53 -0700
Re: Aliasing and subtyping structs supercat@casperkitty.com - 2016-11-04 09:56 -0700
Re: Aliasing and subtyping structs Andreas <nospam@invalid.invalid> - 2016-11-08 21:53 +0100
Re: Aliasing and subtyping structs James Kuyper <jameskuyper@verizon.net> - 2016-11-01 11:41 -0400
Re: Aliasing and subtyping structs Andreas <nospam@invalid.invalid> - 2016-11-02 09:55 +0100
"Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Anton Shepelev <anton.txt@g{oogle}mail.com> - 2016-11-21 16:59 +0300
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] supercat@casperkitty.com - 2016-11-21 07:32 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] "James R. Kuyper" <jameskuyper@verizon.net> - 2016-11-21 11:15 -0500
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] supercat@casperkitty.com - 2016-11-21 08:35 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Anton Shepelev <anton.txt@g{oogle}mail.com> - 2016-11-22 11:42 +0300
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] supercat@casperkitty.com - 2016-11-22 06:50 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-11-22 16:07 +0000
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] supercat@casperkitty.com - 2016-11-22 12:02 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-11-22 23:36 +0000
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] supercat@casperkitty.com - 2016-11-22 16:24 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Richard Damon <Richard@Damon-Family.org> - 2016-11-22 22:21 -0500
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] supercat@casperkitty.com - 2016-11-23 08:31 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] me <crisdunbar@gmail.com> - 2016-11-23 09:01 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] supercat@casperkitty.com - 2016-11-23 12:05 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Anton Shepelev <anton.txt@gmail.com> - 2016-11-22 23:23 +0300
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] "James R. Kuyper" <jameskuyper@verizon.net> - 2016-11-22 16:02 -0500
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] supercat@casperkitty.com - 2016-11-22 14:13 -0800
Re: container_of() macro Noob <root@127.0.0.1> - 2016-11-23 01:10 +0100
Re: container_of() macro <william@wilbur.25thandClement.com> - 2016-11-22 20:10 -0800
Re: container_of() macro "Chris M. Thomasson" <invalid@invalid.invalid> - 2016-11-23 15:10 -0800
Re: container_of() macro David Brown <david.brown@hesbynett.no> - 2016-11-23 11:31 +0100
Re: container_of() macro Anton Shepelev <anton.txt@g{oogle}mail.com> - 2016-11-23 14:07 +0300
Re: container_of() macro supercat@casperkitty.com - 2016-11-23 08:41 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Anton Shepelev <anton.txt@gmail.com> - 2016-11-30 00:14 +0300
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] "James R. Kuyper" <jameskuyper@verizon.net> - 2016-11-29 17:23 -0500
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Anton Shepelev <anton.txt@gmail.com> - 2016-12-04 18:48 +0300
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] "James R. Kuyper" <jameskuyper@verizon.net> - 2016-12-04 12:17 -0500
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Anton Shepelev <anton.txt@gmail.com> - 2016-12-04 22:15 +0300
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] "James R. Kuyper" <jameskuyper@verizon.net> - 2016-12-04 15:06 -0500
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Anton Shepelev <anton.txt@gmail.com> - 2016-12-12 22:31 +0300
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] "Chris M. Thomasson" <invalid@invalid.invalid> - 2016-11-23 13:39 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] luser droog <luser.droog@gmail.com> - 2016-11-23 15:10 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] "Chris M. Thomasson" <invalid@invalid.invalid> - 2016-11-23 15:13 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] luser droog <luser.droog@gmail.com> - 2016-11-23 18:29 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Anton Shepelev <anton.txt@g{oogle}mail.com> - 2016-11-24 11:41 +0300
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Thiago Adams <thiago.adams@gmail.com> - 2016-11-24 03:29 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] "Chris M. Thomasson" <invalid@invalid.invalid> - 2016-11-24 17:37 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] supercat@casperkitty.com - 2016-11-25 09:55 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Thiago Adams <thiago.adams@gmail.com> - 2016-11-25 15:22 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] "Chris M. Thomasson" <invalid@invalid.invalid> - 2016-11-28 18:18 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Thiago Adams <thiago.adams@gmail.com> - 2016-11-29 04:48 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] supercat@casperkitty.com - 2016-11-29 07:28 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Thiago Adams <thiago.adams@gmail.com> - 2016-11-30 08:26 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] supercat@casperkitty.com - 2016-11-30 09:13 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] "Chris M. Thomasson" <invalid@invalid.invalid> - 2016-12-12 16:44 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Melzzzzz <mel@zzzzz.com> - 2016-12-13 02:18 +0100
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Thiago Adams <thiago.adams@gmail.com> - 2016-12-14 09:47 -0800
Re: "Object-oriented programming in C" [was: Re: Aliasing and subtyping structs] Thiago Adams <thiago.adams@gmail.com> - 2016-12-14 10:14 -0800
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