[PATCH] include: Declare getopt function on old GNU libc

[Pedro Alves]

On 2022-10-16 2:12 p.m., Tsukasa OI wrote:
> On 2022/10/13 20:59, Pedro Alves wrote:
>> On 2022-10-13 11:11 a.m., Tsukasa OI via Binutils wrote:
>>> On GNU libc <= 2.25, <unistd.h> includes <getopt.h> with __need_getopt macro
>>> defined.  That <getopt.h> is intended to be a part of GNU libc but
>>> <unistd.h> actually includes include/getopt.h in this project.
>>
>> Messy.
> 
> Well, I have to agree.
> 
>>
>> Do we really still need this getopt.h header?
>>
>> gnulib, at:
>>
>>  https://www.gnu.org/software/gnulib/manual/html_node/getopt_002eh.html
>>
>> says:
>>
>>   "This header file is missing on some platforms: AIX 5.1, HP-UX 11, MSVC 14."
>>
>> AIX 5.1 is from 2001.
>> HP-UX 11 is from 1997.
>> We don't support building with MSVC AFAIK.
>>
>> Can't we just get rid of it?
>>
> 
> I feel this is too unsafe to do that

Why?  Are you aware of any host system that people actually build binutils on
that doesn't have a proper getopt declaration?

> (unless you assume getopt_long and
> getopt_long_only are always available on the system).

getopt is supposed to be declared in unistd.h.  The .c files that
use getopt (not the GNU extensions) could just switch to including
that one.

Even if there is such a system, I would think that a better fix would
be to rename include/getopt.h to something else, and have that header include
<getopt.h> and/or do whatever else needed to pick the right declarations on the system.
A standard header replacement that doesn't #include_next the original is just asking
for trouble, like we've run into...

> 
> Even if this patch is unacceptable, I don't want to revert previous
> changes to sim/configure{,.ac} either (it's necessary to prevent a build
> failure with Clang).  

It's only necessary because of this hacky include/getopt.h header existing, no?.
Why would you want to keep the configure.ac bits if the hacky header with the
unprototyped declaration doesn't exist any more?

Thanks,
Pedro Alves

> It's also a hack but to stop using getopt
> (entirely) may be an option, changing following files:
> 
> -   sim/igen/igen.c
> -   sim/m32c/main.c
> -   sim/rl78/main.c
> 
> I mean, we could replace getopt with getopt_long plus dummy longopts.
> This way, CentOS (7) regression will (also) be gone.
> 
> What do you think?
> 
> Thanks,
> Tsukasa
>