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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: "A diagram of C23 basic types"
Date: Wed, 09 Apr 2025 15:01:59 -0700
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Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
[...]
> 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.

I believe a diagnotic is required.

C17 5.1.1.3:

    A conforming implementation shall produce at least one
    diagnostic message (identified in an implementation-defined
    manner) if a preprocessing translation unit or translation
    unit contains a violation of any syntax rule or constraint,
    even if the behavior is also explicitly specified as undefined
    or implementation-defined.

A trailing comma on an argument or parameter list is a violation
of a syntax rule.

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