Re: [PATCH v2] for_each_string_list_item: avoid undefined behavior for empty list

From: Junio C Hamano <gitster@pobox.com>
Date: Sep 21, 2017, 01:12 UTC
Message-ID: <xmqqtvzwn9bj.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <87lgl9rqbq.fsf@linux-m68k.org>

Andreas Schwab <schwab@linux-m68k.org> writes:

Show 24 quoted lines

> On Sep 20 2017, Jonathan Nieder <jrnieder@gmail.com> wrote:
>
>> Andreas Schwab wrote:
>>> On Sep 19 2017, Jonathan Nieder <jrnieder@gmail.com> wrote:
>>
>>>> B. #define for_each_string_list_item(item, list) \
>>>> 	if (list->items) \
>>>> 		for (item = ...; ...; ... )
>>>>
>>>>    This breaks a caller like
>>>> 	if (foo)
>>>> 		for_each_string_list_item(item, list)
>>>> 			...
>>>> 	else
>>>> 		...
>>>>
>>>>    making it a non-starter.
>>>
>>> That can be fixed with a dangling else.
>>
>> I believe the fix you're referring to is option C, from the same email
>> you are replying to.  If not, please correct me.
>
> A variant thereof, yes.

Now you make me curious. How would that variant be different from option C. in Jonathan's message? Perhaps that different version may be a solution to work around the potential issue mentioned in the description of option C.?