Re: func is not a keyword

From	Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups	comp.lang.c
Subject	Re: __func__ is not a keyword
Date	2025-03-16 11:51 -0700
Organization	None to speak of
Message-ID	<87bju0x10g.fsf@nosuchdomain.example.com> (permalink)
References	<vr4lgu$63fu$1@dont-email.me> <87bju2htxy.fsf@nosuchdomain.example.com> <6sCBP.1140938$t84d.713135@fx11.iad>

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scott@slp53.sl.home (Scott Lurndal) writes:
> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>Thiago Adams <thiago.adams@gmail.com> writes:
>>> This program does not compile..in gcc and clang
>>>
>>> int __func__  i =1;
>>
>>I'm mildly curious how gcc and clang treat "__func__" internally
>>that leads to this odd behavior. 
>
> From the gcc info page:
>
>    GCC provides three magic variables that hold the name of the current
>    function, as a string.  The first of these is '__func__', which is part
>    of the C99 standard:
>
>     The identifier '__func__' is implicitly declared by the translator as
>    if, immediately following the opening brace of each function definition,
>    the declaration
>
>      static const char __func__[] = "function-name";
>
>    appeared, where function-name is the name of the lexically-enclosing
>    function.  This name is the unadorned name of the function.

But that doesn't tell us how it's treated internally and it's
inconsistent with gcc's actual behavior.  Both a look at gcc's
source code and its behavior indicate that gcc treats __func__ as
a keyword, which is inconsistent with the info page.  For example,
one would expect this:

int main(void) {
    {
        int __func__;
    }
}

to be accepted, with the inner definition of __func__ hiding the
implicit static declaration, but gcc reports a syntax error.

It's not a conformance issue, since __func__ is a reserved identifier
and any code that can tell whether it's a keyword has undefined
behavior.

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

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Thread

__func__ is not a keyword Thiago Adams <thiago.adams@gmail.com> - 2025-03-15 16:47 -0300
  Re: __func__ is not a keyword Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-15 14:20 -0700
    Re: __func__ is not a keyword Thiago Adams <thiago.adams@gmail.com> - 2025-03-15 18:30 -0300
      Re: __func__ is not a keyword Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-15 14:53 -0700
        Re: __func__ is not a keyword Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-15 15:04 -0700
    Re: __func__ is not a keyword Kaz Kylheku <643-408-1753@kylheku.com> - 2025-03-16 07:18 +0000
      Re: __func__ is not a keyword Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-16 02:06 -0700
        Re: __func__ is not a keyword Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-03-18 10:00 -0700
    Re: __func__ is not a keyword scott@slp53.sl.home (Scott Lurndal) - 2025-03-16 15:51 +0000
      Re: __func__ is not a keyword Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-16 11:51 -0700
        Re: __func__ is not a keyword Kaz Kylheku <643-408-1753@kylheku.com> - 2025-03-16 19:05 +0000
          Re: __func__ is not a keyword Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-16 13:29 -0700
            Re: __func__ is not a keyword Kaz Kylheku <643-408-1753@kylheku.com> - 2025-03-17 17:03 +0000
              Re: __func__ is not a keyword Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-17 13:09 -0700
                Re: __func__ is not a keyword Kaz Kylheku <643-408-1753@kylheku.com> - 2025-03-17 20:31 +0000
          Re: __func__ is not a keyword James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-03-16 16:35 -0400
  Re: __func__ is not a keyword Mario Rosell <usenet@mariorosell.es> - 2026-04-17 20:19 +0000
    Re: __func__ is not a keyword Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-04-17 14:15 -0700

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