On Mon, Jan 22, 2018 at 4:59 PM, Jeff King <peff@xxxxxxxx> wrote:
> On Mon, Jan 22, 2018 at 07:54:18PM -0500, Eric Sunshine wrote:
>
>> On Mon, Jan 22, 2018 at 6:51 PM, Elia Pinto <gitter.spiros@xxxxxxxxx> wrote:
>> > This patch add explicit fallthrough compiler attribute
>> > when needed on switch case statement eliminating
>> > the compile warning [-Werror=implicit-fallthrough=].
>> > It does this by means of a macro that takes into account
>> > the versions of the compilers that include that attribute.
>> > [...]
>> > Signed-off-by: Elia Pinto <gitter.spiros@xxxxxxxxx>
>> > ---
>> > diff --git a/convert.c b/convert.c
>> > @@ -1554,7 +1554,7 @@ static int ident_filter_fn(struct stream_filter *filter,
>> > switch (ident->state) {
>> > default:
>> > strbuf_add(&ident->left, head, ident->state);
>> > - /* fallthrough */
>> > + GIT_FALLTHROUGH;
>> > case IDENT_SKIPPING:
>> > /* fallthrough */
>>
>> Why doesn't this /* fallthrough */ deserve the same treatment?
>>
>> > case IDENT_DRAINING:
>
> I can't answer that philosophically, but I can tell you why the compiler
> does not complain. :)
>
> Usually case arms with no statements between them are exempt from
> fallthrough warnings. So:
>
> switch (foo)
> case 1:
> case 2:
> case 3:
> /* do one thing */
> break;
> case 4:
> /* do another thing */
> break;
> }
>
> does not need any annotations for cases 1 and 2 to fallthrough. Which
> means that the original comment was not actually necessary for the
> compiler, though the original author considered it a useful comment.
>
> So there you get into philosophy. Should it be converted to a
> compiler-visible annotation, or is it better left as a comment?
>
> -Peff
I'd personally rather stick to the comment if we can, or use something
like "fallthrough;" to make it appear like a keyword, instead of an
all caps macro, since at least to my sensibility, the all caps is a
bit too crazy.
Also, I would not put one inside an empty case statement that just
falls through to the next branch and does nothing special itself.
Thanks,
Jake
