Re: [PATCH v2] specify void prototype for functions with no parameters

Khem Raj <[email protected]> Thu, 1 Sep 2022 09:53:44 -0700

Newsgroups	gmane.comp.sysutils.autoconf.patches
Message-ID	<[email protected]>

On 8/30/22 2:53 PM, Paul Eggert wrote:
> On 8/29/22 21:35, Khem Raj wrote:
>> Compilers defaulting to C99 flag such functions as warning which fails
>> to compile when using -Werror
> 
> As mentioned earlier, projects should not use -Werror when configuring, 
> for several reasons (this is just one). After you mentioned rsync was 
> using something like -Werror I sent in a patch to the rsync folks, and 
> rsync has been fixed:
> 
> https://github.com/WayneD/rsync/commit/9a3449a3980421f84ac55498ba565bc112b20d6c
> 
> What other projects are doing it? They should be fixed too, regardless 
> of whether we change Autoconf here.
> 
> As for Autoconf, if we're going to make this change at all, we should do 
> it fully. Something like the attached patch, perhaps. I haven't 
> installed it.

Thanks, I tried this patch over mine and I ran into few problems. Some 
of them were latent issues[1] but some are problems[2] especially  using 
AC_CHECK_FUNCS when default compiler is C++ compiler not C compiler

A code snippet like below it generated

#include <limits.h>
#undef pipe

/* Override any GCC internal prototype to avoid an error.
Use char because int might match the return type of a GCC
builtin and then its argument prototype would still apply.  */
char pipe (int);
/* The GNU C library defines this for functions which it implements
to always fail with ENOSYS.  Some functions are actually named
something starting with __ and the normal name is an alias.  */
#if defined __stub_pipe || defined __stub___pipe
choke me
#endif

int
main (void)
{
return pipe (0);
;
return 0;
}

When this is compiled with C compiler it links fine, however when using 
C++ compiler this fails to link

% cc a.c

% c++ a.c
/usr/bin/ld: /tmp/ccRkgy7K.o: in function `main':
a.c:(.text+0xa): undefined reference to `pipe(int)'
collect2: error: ld returned 1 exit status

[1] https://gitlab.xfce.org/xfce/xfce4-dev-tools/-/issues/57
[2] https://errors.yoctoproject.org/Errors/Details/671040/

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