From: Bjørn Mork
> Sent: 28 October 2017 11:57
> > In preparation to enabling -Wimplicit-fallthrough, mark switch cases
> > where we are expecting to fall through.
> >
> > Notice that in this particular case I replaced "...drop on through"
> > comments with a proper "fall through" comment on its own line, which
> > is what GCC is expecting to find.
>
> Sounds to me like GCC is the wrong tool for this. But I would of course
> not mind if it was *just* the text. However, as your patch cleary
> shows, the simplified logic leads to real problems:
>
> > @@ -1819,8 +1819,8 @@ static void process_rcvd_data(struct edgeport_serial *edge_serial,
> > edge_serial->rxState = EXPECT_DATA;
> > break;
> > }
> > - /* Else, drop through */
> > }
> > + /* fall through */
> > case EXPECT_DATA: /* Expect data */
> > if (bufferLength < edge_serial->rxBytesRemaining) {
> > rxLen = bufferLength;
>
>
> The original comment clearly marked a *conditional* fall through at the
> correct place. Your patch makes it appear as if there is an
> unconditional fall through here. There is not. The fallthrough only
> applies to one of a number of nested if blocks. There are no less than
> 3 break statements in the same case block.
>
> Not a big deal maybe, just as the lack of any "fall through" comment
> isn't a big deal in the first place. But this change is clearly making
> this code harder to read, and the change is therefore harmful IMHO.
>
> If you can't make -Wimplicit-fallthrough work without removing such
> precise fallthrough markings, then my proposal is to drop it and use
> some other tool.
Just remove the 'else' after the 'break' further up.
David
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