Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.lang.c++ > #85620
| From | Ben Bacarisse <ben.usenet@bsb.me.uk> |
|---|---|
| Newsgroups | comp.lang.c++ |
| Subject | Re: Differences between C and C++ |
| Date | 2022-07-25 17:14 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <87k081tbjm.fsf@bsb.me.uk> (permalink) |
| References | <tbm4vp$obp$1@gioia.aioe.org> |
Juha Nieminen <nospam@thanks.invalid> writes:
> Some people often object if someone conflates C and C++, as if C++ were
> just a pure superset of C, pointing out that they are, in fact, different
> languages and, in some aspects, actually incompatible with each other.
>
> That got me thinking: What are all the differences between the two
> languages, in behavior and meaning, when it comes to their common
> syntax?
Let's see...
"abc" is of type char * in C and of type const char * in C++.
Then there all the keyword differences. For example, in C, new is an
ordinary ID and in C++ restrict is an ordinary ID. There are quite a
few of these!
The rules for compatible pointer types are stronger in C++. Basically,
you can only add a top-level const when passing arguments in C.
In C++ function declarations, () means (void), but in C it means an
old-style function with unspecified arguments.
In C, at file scope, int x[]; is a "tentative definition" (which will
resolve to int x[] = {0}; if there are no further declarations of x) but
in C++ it's just an error.
In C, f( (int[]){1} ), calls f with a temporary array (it's a "compound
literal"), but that's forbidden in C++.
Some things that are compound literals in C /are/ valid in C++. For
example:
struct s { int v; };
...
f((struct s){1});
is ok in both, but add a pointer and you get the same difference as
above:
g(&(struct s){1}); // ok in C, not ok in C++
And now I'm out of time...
> In other words, I'm not here talking about different keywords and different
> syntax that compiles in one but not the other. I'm talking about code that
> does compile as both C and C++, but will be interpreted or behave
> differently depending on which (and this makes them incompatible).
>
> Here are some of the things that come to mind. What other things are there?
>
> 1) A 'const' variable at the global scope will have external linkage by
> default in C (unless explicitly made to have internal linkage with
> 'static'), but internal linkage by default in C++ (unless explicitly made
> to have external linkage with 'extern').
>
> 2) The type of 'A' is int in C, but char in C++.
>
> 3) This one is really obscure: In C, this:
>
> int f(int (*)(), double (*)[3]);
> int f(int (*)(char *), double (*)[]);
>
> is a valid function declaration, and equivalent to:
>
> int f(int (*)(char *), double (*)[3]);
Yes. This is C's rules for "composite types" in action.
> (This one is so obscure that I'm certain the vast majority of C programmers,
> even experienced ones, would be surprised it even compiles. However, the
> example is directly from the C standard, so it's pretty legit.)
>
> In C++ the two first lines declare two different functions, taking different
> types of parameter. Calling one is not the same thing as calling the
> other.
However, you can, in fact call the second f with a double (*)[] argument
because of C++'s rules about similar types (at least I think those are
the rules that apply here).
--
Ben.
Back to comp.lang.c++ | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Differences between C and C++ Juha Nieminen <nospam@thanks.invalid> - 2022-07-25 13:14 +0000
Re: Differences between C and C++ "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-07-25 16:18 +0200
Re: Differences between C and C++ Paavo Helde <eesnimi@osa.pri.ee> - 2022-07-25 18:47 +0300
Re: Differences between C and C++ Paavo Helde <eesnimi@osa.pri.ee> - 2022-07-25 19:49 +0300
Re: Differences between C and C++ Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-25 19:38 +0100
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-07-25 08:51 -0700
Re: Differences between C and C++ Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-25 17:14 +0100
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-25 16:19 +0000
Re: Differences between C and C++ Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-25 19:28 +0100
Re: Differences between C and C++ Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-25 12:21 -0700
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-26 07:54 +0000
Re: Differences between C and C++ Juha Nieminen <nospam@thanks.invalid> - 2022-07-26 08:00 +0000
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-26 08:09 +0000
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-07-26 02:42 -0700
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-26 15:29 +0000
Re: Differences between C and C++ scott@slp53.sl.home (Scott Lurndal) - 2022-07-26 16:30 +0000
Re: Differences between C and C++ Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-26 11:59 -0700
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-27 07:52 +0000
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-07-27 01:56 -0700
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-27 14:51 +0000
Re: Differences between C and C++ Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-27 11:11 -0700
Re: Differences between C and C++ Juha Nieminen <nospam@thanks.invalid> - 2022-07-26 06:09 +0000
Re: Differences between C and C++ Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-27 17:33 +0100
Re: Differences between C and C++ Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2022-07-25 17:45 +0100
Re: Differences between C and C++ Paul N <gw7rib@aol.com> - 2022-07-27 10:09 -0700
Re: Differences between C and C++ Bo Persson <bo@bo-persson.se> - 2022-07-27 19:28 +0200
Re: Differences between C and C++ Paul N <gw7rib@aol.com> - 2022-07-27 11:43 -0700
Re: Differences between C and C++ David Brown <david.brown@hesbynett.no> - 2022-07-29 18:04 +0200
Re: Differences between C and C++ Richard Damon <Richard@Damon-Family.org> - 2022-07-29 18:47 -0400
Re: Differences between C and C++ David Brown <david.brown@hesbynett.no> - 2022-07-30 14:08 +0200
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-28 08:03 +0000
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-07-28 01:57 -0700
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-28 09:04 +0000
Re: Differences between C and C++ Juha Nieminen <nospam@thanks.invalid> - 2022-07-28 06:53 +0000
Re: Differences between C and C++ Richard Damon <Richard@Damon-Family.org> - 2022-07-28 07:33 -0400
Re: Differences between C and C++ Bo Persson <bo@bo-persson.se> - 2022-07-28 15:04 +0200
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-28 15:11 +0000
Re: Differences between C and C++ Paavo Helde <eesnimi@osa.pri.ee> - 2022-07-28 20:03 +0300
Re: Differences between C and C++ Juha Nieminen <nospam@thanks.invalid> - 2022-07-29 07:56 +0000
Re: Differences between C and C++ Paavo Helde <eesnimi@osa.pri.ee> - 2022-07-29 12:03 +0300
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-29 09:28 +0000
Re: Differences between C and C++ Juha Nieminen <nospam@thanks.invalid> - 2022-07-29 12:27 +0000
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-07-29 05:43 -0700
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-29 14:14 +0000
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-07-29 08:25 -0700
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-29 15:48 +0000
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-07-29 13:12 -0700
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-30 09:28 +0000
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-07-30 03:39 -0700
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-30 14:23 +0000
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-07-30 19:07 -0700
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-31 07:22 +0000
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-07-31 06:07 -0700
Re: Differences between C and C++ muttley@dastardlyhq.com - 2022-07-31 16:36 +0000
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-08-01 01:12 -0700
Re: Differences between C and C++ Juha Nieminen <nospam@thanks.invalid> - 2022-07-29 22:47 +0000
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-07-30 03:48 -0700
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-07-29 05:16 -0700
Re: Differences between C and C++ Manfred <noname@add.invalid> - 2022-07-30 02:14 +0200
Re: Differences between C and C++ Juha Nieminen <nospam@thanks.invalid> - 2022-07-31 14:39 +0000
Re: Differences between C and C++ "Fred. Zwarts" <F.Zwarts@KVI.nl> - 2022-07-31 18:49 +0200
Re: Differences between C and C++ Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-31 14:49 -0700
Re: Differences between C and C++ Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-31 17:03 -0700
Re: Differences between C and C++ Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-08-01 00:16 -0700
Re: Differences between C and C++ Ike Naar <ike@sdf.org> - 2022-08-01 07:27 +0000
Re: Differences between C and C++ Paavo Helde <eesnimi@osa.pri.ee> - 2022-08-01 10:47 +0300
Re: Differences between C and C++ Paavo Helde <eesnimi@osa.pri.ee> - 2022-08-01 10:34 +0300
Re: Differences between C and C++ Manfred <noname@add.invalid> - 2022-08-03 01:20 +0200
Re: Differences between C and C++ Juha Nieminen <nospam@thanks.invalid> - 2022-08-03 07:59 +0000
Re: Differences between C and C++ Bo Persson <bo@bo-persson.se> - 2022-08-03 12:45 +0200
Re: Differences between C and C++ Juha Nieminen <nospam@thanks.invalid> - 2022-08-03 10:53 +0000
Re: Differences between C and C++ Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-08-03 03:58 -0700
Re: Differences between C and C++ Paavo Helde <eesnimi@osa.pri.ee> - 2022-08-03 14:49 +0300
Re: Differences between C and C++ Öö Tiib <ootiib@hot.ee> - 2022-08-03 23:31 -0700
Re: Differences between C and C++ Juha Nieminen <nospam@thanks.invalid> - 2022-08-01 11:29 +0000
Re: Differences between C and C++ Bo Persson <bo@bo-persson.se> - 2022-08-01 14:39 +0200
Re: Differences between C and C++ Juha Nieminen <nospam@thanks.invalid> - 2022-08-02 05:43 +0000
Re: Differences between C and C++ Manfred <noname@add.invalid> - 2022-08-03 01:13 +0200
Re: Differences between C and C++ Paavo Helde <eesnimi@osa.pri.ee> - 2022-08-03 09:34 +0300
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-29 09:22 +0000
Re: Differences between C and C++ Paavo Helde <eesnimi@osa.pri.ee> - 2022-07-29 13:53 +0300
Re: Differences between C and C++ Paavo Helde <eesnimi@osa.pri.ee> - 2022-07-29 14:13 +0300
Re: Differences between C and C++ Muttley@dastardlyhq.com - 2022-07-29 14:11 +0000
Re: Differences between C and C++ Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-28 06:16 -0700
csiph-web