Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: "A diagram of C23 basic types"
Date: Fri, 04 Apr 2025 19:15:50 -0700
Organization: None to speak of
Lines: 38
Message-ID: <85semnica1.fsf@nosuchdomain.example.com>
References: <87y0wjaysg.fsf@gmail.com> <vsj1m8$1f8h2$1@dont-email.me>
	<vsj2l9$1j0as$1@dont-email.me> <vsjgk0$207gb$1@paganini.bofh.team>
	<vsjkc8$252sk$1@dont-email.me> <vspvqk$sl3u$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain
Injection-Date: Sat, 05 Apr 2025 04:16:10 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="959afc724390e84815a36c37a7f67456";
	logging-data="1070926"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+QVa4UD/UCigIE/amUWhhm"
User-Agent: Gnus/5.13 (Gnus v5.13)
Cancel-Lock: sha1:TML2ywMrZjYEZha5SAKMCrNw7RE=
	sha1:izxxMgcKz9dEupiavtcrOlx8oG8=

James Kuyper <jameskuyper@alumni.caltech.edu> writes:
> Muttley@dastardlyhq.org wrote:
>> On Wed, 2 Apr 2025 14:12:18 -0000 (UTC)
>> antispam@fricas.org (Waldek Hebisch) wibbled:
> ...
>>>C99 has VMT (variable modified types).  Thanks to VMT and complex types
>>>C99 can naturaly do numeric computing that previously was done using
>>>Fortran 77.  Offical C++ has no VMT.  C++ mechanizms look nicer,
>> 
>> Officially no, but I've never come across a C++ compiler that didn't support
>> them given they're all C compilers too.
>
> There exist many programs that can compile either C code and C++ code,
> depending either upon the extension of the file name or explicit command
> line options to determine which language's rules to apply. That doesn't
> qualify. Do you know of any compiler that accepts VMTs when compiling
> according to C++ rules? If so, please provide an example. It will help
> if the code has some features that are well-formed code in C++, but
> syntax errors in C, to make it clear that C++'s rules are being implemented.

g++ and clang++ both do so:

int main() {
    class foo { };
    int len = 42;
    int vla[len];
}

Both warn about the variable length array when invoked with "-pedantic"
and reject it with "-pedantic-errors".

Microsoft's C and C++ compilers do not support VLAs.  (Their C compiler
never supported C99, and VLAs were made optional in C11, so that's not a
coformance issue.)

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */