Messages in this thread | | | From | Bjørn Mork <> | Subject | Re: [PATCH] USB: serial: io_edgeport: mark expected switch fall-throughs | Date | Sat, 28 Oct 2017 12:56:51 +0200 |
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"Gustavo A. R. Silva" <garsilva@embeddedor.com> writes:
> 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.
Bjørn
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