lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Sat, 28 Oct 2017 12:56:51 +0200 From: Bjørn Mork <bjorn@...k.no> To: "Gustavo A. R. Silva" <garsilva@...eddedor.com> Cc: Johan Hovold <johan@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] USB: serial: io_edgeport: mark expected switch fall-throughs "Gustavo A. R. Silva" <garsilva@...eddedor.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
Powered by blists - more mailing lists