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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.lang.c
Subject: Re: "A diagram of C23 basic types"
Date: Wed, 09 Apr 2025 13:14:55 -0700
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Michael S <already5chosen@yahoo.com> writes:

> On Fri, 4 Apr 2025 02:57:10 -0000 (UTC)
> Lawrence D'Oliveiro <ldo@nz.invalid> wrote:
>
>> On Thu, 3 Apr 2025 21:48:40 +0100, bart wrote:
>>
>>> Commas are overwhelmingly used to separate list elements in
>>> programming languages.
>>
>> Not just separate, but terminate.
>
> I disagree.  I am in favor of optional trailing commas rather than
> mandatory ones.
>
>> All the reasonable languages allow
>> trailing commas.
>
> Are your sure that C Standard does not allow trailing commas?
> That is, they are obviously legal in initializer lists.
> All compilers that I tried reject trailing comma in function calls.
>
> For example
>
> void bar(int);
> void foo(void) {
>   bar(1,);
> }
>
> MSVC:
> comma.c(3): error C2059:  syntax error: ')'
>
> clang:
> comma.c:3:9: error: expected expression
>     3 |   bar(1,);
>       |         ^
>
> gcc:
> comma.c:  In function 'foo':
> comma.c:3:9: error: expected expression before ')' token
>     3 |   bar(1,);
>       |         ^
> comma.c:3:3: error: too many arguments to function 'bar'
>     3 |   bar(1,);
>       |   ^~~
> comma.c:1:6: note:  declared here
>     1 | void bar(int);
>       |      ^~~
>
> But is it (rejection) really required by the Standard?  I don't know.

It is required in the sense that it is a syntax error,
and syntax errors require a diagnostic.

Trailing commas in argument lists and/or parameter lists
could be accepted as an extension, even without giving a
diagnostic as I read the C standard, but implementations
are certainly within their rights to reject them.