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Re: The variable __func__ in C89 in gcc

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On 05/19/2011 05:03 AM, Sorc Chan wrote:
> On 18 май, 18:08, rouben@shady.(none) (Rouben Rostamian) wrote:
>> Consider:
>>
>> #include <stdio.h>
>> int main(void)
>> {
>>         printf("entering function %s\n", __func__);
>>         return 0;
>>
>> }
>>
>> Gcc compiles this program without a warning, even
>> in C89 mode, as in "gcc -Wall -pedantic -std=c89 progname.c".
>>
>> I expected to see a warning since the identifier __func__ was
>> introduced in C99.  Is there a good reason why the compilation
>> does not fail in the C89 mode?
>>
>> --
>> Rouben Rostamian
> 
> int main(void) {
>     __func__;
>     return 0;
> }
> 
> $ gcc -S main1.c -Wall -pedantic -std=c89 -o main1.s && cat main1.s
> main1.c: In function ‘main’:
> main1.c:2: warning: statement with no effect
> 	.file	"main1.c"
> 	.text
> .globl main
> 	.type	main, @function
> main:
> 	pushl	%ebp
> 	movl	%esp, %ebp
> 	movl	$0, %eax
> 	popl	%ebp
> 	ret
> 	.size	main, .-main
> 	.section	.rodata
> 	.type	__func__.869, @object
> 	.size	__func__.869, 5
> __func__.869:
> 	.string	"main"
> 	.ident	"GCC: (GNU) 4.4.4 20100630 (Red Hat 4.4.4-10)"
> 	.section	.note.GNU-stack,"",@progbits
> $
> 
> Dat GCC epic fail IMHO.

It might be an "epic failure" to meet some arbitrary requirement that
you've chosen to impose; but it does not indicate a failure to meet the
requirements imposed by the C89 standard.

>>> What would _prevent_ GCC from providing this for C89 code?
> 
> Because __func__ in C98 undeclared such as any __ohhelloguys__ thing.

C89 imposes no such requirement. In fact, the main reason why the C89
standard said that a program using __func__ has undefined behavior is so
an implementation can choose to do anything it wishes to do with
__func__. In particular, the fact that the behavior is undefined gives
the compiler permission to treat __func__ as behaving in precisely the
fashion it's required to behave, according to the C99 standard. It also
gives it permission to treat __func__ as an indication that it should
use your program to generate Funk music.
-- 
James Kuyper

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The variable __func__ in C89 in gcc rouben@shady.(none) (Rouben Rostamian) - 2011-05-18 14:08 +0000
  Re: The variable __func__ in C89 in gcc Shao Miller <sha0.miller@gmail.com> - 2011-05-18 10:13 -0400
  Re: The variable __func__ in C89 in gcc Seebs <usenet-nospam@seebs.net> - 2011-05-18 16:03 +0000
    Re: The variable __func__ in C89 in gcc Keith Thompson <kst-u@mib.org> - 2011-05-18 10:32 -0700
      Re: The variable __func__ in C89 in gcc cri@tiac.net (Richard Harter) - 2011-05-18 19:39 +0000
        Re: The variable __func__ in C89 in gcc Seebs <usenet-nospam@seebs.net> - 2011-05-18 19:45 +0000
      Re: The variable __func__ in C89 in gcc William Ahern <william@wilbur.25thandClement.com> - 2011-05-18 19:27 -0700
    Re: The variable __func__ in C89 in gcc Keith Thompson <kst-u@mib.org> - 2011-05-19 08:42 -0700
      Re: The variable __func__ in C89 in gcc Seebs <usenet-nospam@seebs.net> - 2011-05-19 16:34 +0000
        Re: The variable __func__ in C89 in gcc Kenneth Brody <kenbrody@spamcop.net> - 2011-05-19 14:15 -0400
        Re: The variable __func__ in C89 in gcc Shao Miller <sha0.miller@gmail.com> - 2011-05-19 14:45 -0400
        Re: The variable __func__ in C89 in gcc Tim Rentsch <txr@alumni.caltech.edu> - 2011-05-19 14:02 -0700
      Re: The variable __func__ in C89 in gcc Tim Rentsch <txr@alumni.caltech.edu> - 2011-05-19 12:45 -0700
  Re: The variable __func__ in C89 in gcc Sorc Chan <sorcchan@gmail.com> - 2011-05-19 02:03 -0700
    Re: The variable __func__ in C89 in gcc James Kuyper <jameskuyper@verizon.net> - 2011-05-19 06:17 -0400
      Re: The variable __func__ in C89 in gcc Tim Rentsch <txr@alumni.caltech.edu> - 2011-05-19 13:44 -0700
        Re: The variable __func__ in C89 in gcc Keith Thompson <kst-u@mib.org> - 2011-05-19 13:48 -0700
          Re: The variable __func__ in C89 in gcc Tim Rentsch <txr@alumni.caltech.edu> - 2011-05-19 14:12 -0700
            Re: The variable __func__ in C89 in gcc Keith Thompson <kst-u@mib.org> - 2011-05-19 14:29 -0700
              Re: The variable __func__ in C89 in gcc gazelle@shell.xmission.com (Kenny McCormack) - 2011-05-19 21:54 +0000
                Re: The variable __func__ in C89 in gcc Angel <angel+news@spamcop.net> - 2011-05-19 22:27 +0000
              Re: The variable __func__ in C89 in gcc Tim Rentsch <txr@alumni.caltech.edu> - 2011-05-24 02:23 -0700
          Re: The variable __func__ in C89 in gcc gazelle@shell.xmission.com (Kenny McCormack) - 2011-05-19 21:54 +0000
          Re: The variable __func__ in C89 in gcc James Kuyper <jameskuyper@verizon.net> - 2011-05-19 23:26 -0400
            Re: The variable __func__ in C89 in gcc Shao Miller <sha0.miller@gmail.com> - 2011-05-19 22:39 -0500
    Re: The variable __func__ in C89 in gcc Shao Miller <sha0.miller@gmail.com> - 2011-05-19 08:22 -0400
      Re: The variable __func__ in C89 in gcc Tim Rentsch <txr@alumni.caltech.edu> - 2011-05-19 13:47 -0700

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