Re: [PATCH v4 1/7] Add delta-islands.{c,h}

> On Mon, Aug 13, 2018 at 01:17:18PM +0100, Ramsay Jones wrote:
>
>> >>> +struct island_bitmap {
>> >>> +     uint32_t refcount;
>> >>> +     uint32_t bits[];
>> >>
>> >> Use FLEX_ARRAY here? We are slowly moving toward requiring
>> >> certain C99 features, but I can't remember a flex array
>> >> weather-balloon patch.
>> >
>> > This was already discussed by Junio and Peff there:
>> >
>> > https://public-inbox.org/git/20180727130229.GB18599@sigill.intra.peff.net/
>>
>> That is a fine discussion, without a firm conclusion, but I don't
>> think you can simply do nothing here:
>>
>>   $ cat -n junk.c
>>        1      #include <stdint.h>
>>        2
>>        3      struct island_bitmap {
>>        4              uint32_t refcount;
>>        5              uint32_t bits[];
>>        6      };
>>        7
>>   $ gcc --std=c89 --pedantic -c junk.c
>>   junk.c:5:11: warning: ISO C90 does not support flexible array members [-Wpedantic]
>>     uint32_t bits[];
>>              ^~~~
>>   $ gcc --std=c99 --pedantic -c junk.c
>
> Right, whether we use the FLEX_ALLOC macros or not, this needs to be
> declared with FLEX_ARRAY, not an empty "[]".