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From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.lang.c
Subject: Re: Baby X is bor nagain
Date: Sun, 30 Jun 2024 17:54:14 +0200
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On 30/06/2024 11:18, Michael S wrote:
> On Sat, 29 Jun 2024 20:55:54 +0100
> bart <bc@freeuk.com> wrote:
> 
>> On 29/06/2024 18:46, Richard Harnden wrote:
>>> On 29/06/2024 15:14, bart wrote:
>>> [...]
>>>> My older bcc compiler reported 4 as a hard error unless an
>>>> override was used.
>>>
>>> But you didn't say anything about main's args.
>>
>> I did, indirectly. The actual error was the use of "()" as an empty
>> parameter list (for any function, not just main, but my example could
>> also have been 'void H(){H(123);}'). If you tried to compile:
>>
>>      int main() {
>>          main(123);
>>      }
>>
>> then it wouldn't get past the () to the call.
>>
>> Eventually I dropped that restriction, and the reason was that so
>> much code used such parameter lists, for any function.
>>
>> Not because they wanted unchecked args (there are some legitimate
>> use-cases within function pointer types), but because so many people
>> assumed () meant zero parameters like (void).
>>
>> Why was such code so common? Presumably because compilers said
>> nothing; and they couldn't because the language allowed it. If they
>> had required an override like mine did, more would have got the
>> message.
>>
> 
> I tried following code:
> int foo() { return 1; }
> 
> Both MSVC and clang warn about it at high warnings level (-Wall for
> MSVC, -Wpedantic for clang). But they dont warn at levels that most
> people use in practice (-W3 or -W4 for MSVC, -Wall for clang).
> gcc13 produces no warning even at -Wpedantic. It does produce warning
> with '-Wpedantic -std=xxx' for all values of xxx except c23 and gnu23.
> The absence of warning for c23/gnu23 makes sense, the rest of gcc
> behavior - less so.
> 

gcc -Wpedantic makes very little sense without specifying a C standard 
(rather than a gnu C standard).

But why would you expect a warning from code that is perfectly legal and 
well-defined C code, without explicitly enabling warnings that check for 
particular style issues?  Non-prototype function declarations are 
deprecated (since C99), but not removed from the language until C23 
(where that declaration is now a function prototype).