Re: [PATCH] gdbsupport: Remove some unnecessary ifdef HAVE_POLL judgments

[Youling Tang <tangyouling@loongson.cn>]

Hi, Pedro
On 05/13/2022 06:21 PM, Pedro Alves wrote:
> On 2022-05-13 11:09, Youling Tang wrote:
>> Hi, Pedro
>>
>> On 05/13/2022 05:28 PM, Pedro Alves wrote:
>>> On 2022-05-13 08:49, Youling Tang wrote:
>>>> By searching event-loop.cc we found that there are only the following 2
>>>> places to assign values to use_poll,
>>>> $ grep -nr use_poll gdbsupport/event-loop.cc
>>>>     88:static unsigned char use_poll = USE_POLL;
>>>>     263:    use_poll = 0;
>>>>
>>>> This USE_POLL is defined as follows,
>>>>    #ifdef HAVE_POLL
>>>>    #define USE_POLL 1
>>>>    #else
>>>>    #define USE_POLL 0
>>>>    #endif
>>>>
>>>> So use_poll may be 1 only if HAVE_POLL is defined. Removed "ifdef
>>>> HAVE_POLL" judgment in use_poll control block.
>>>>
>>>> Signed-off-by: Youling Tang <tangyouling@loongson.cn>
>>> Maybe I'm missing something, but ISTM this can't possible work on hosts that don'
>>>    have poll at all.  Like e.g., mingw:
>>>
>>>    $ grep POLL *
>>>    config.h:/* #undef HAVE_POLL */
>>>    config.h:/* #undef HAVE_POLL_H */
>>>    config.h:/* #undef HAVE_SYS_POLL_H */
>>>
>>> Surely they'll fail to compile after the patch?
>> You are right my oversight.
>>
>> But we can remove these internal_error handling, similar to the following modification:
> We can remove _every_ internal_error call in GDB, since by design, they are not supposed
> to ever execute, unless we have something wrong.  This is the scenario here, guarding against
> someone mistakenly doing that change that would result in use_poll as 1 on a host that doesn't
> support poll.  Why change it?
Thank you for letting me know the design background, this change is not 
needed.

Thanks,
Youling