Re: [libvirt] [PATCH 3/4] qemu: add missing break in qemuDomainDeviceCalculatePCIConnectFlags

On Thu, Feb 23, 2017 at 11:38:40AM +0100, Martin Kletzander wrote: > On Thu, Feb 23, 2017 at 09:48:48AM +0000, Daniel P. Berrange wrote: > > On Wed, Feb 22, 2017 at 09:19:15PM +0100, Martin Kletzander wrote: > > > On Wed, Feb 22, 2017 at 02:44:01PM -0500, Laine Stump wrote: > > > > On 02/22/2017 12:52 PM, Daniel P. Berrange wrote: > > > > > One of the conditions in qemuDomainDeviceCalculatePCIConnectFlags > > > > > was missing a break that could result it in falling through to > > > > > an incorrect codepath. > > > > > > > > Actually that's not true. Every codepath of the preceding case ends with > > > > a "return blah". This is true for the entire function - every case of > > > > every switch in the function ends with "return blah". The entire purpose > > > > of the function is to determine the flags value, and there are no > > > > resources that need cleaning up before returning, so as soon as the > > > > value is determined, it immediately returns. > > > > > > > > I suppose it could be rewritten to change all of those into "ret = blah; > > > > break;", then "return ret;" at the end, but it seemed safer to return > > > > immediately than to trust that no new code would be added later in the > > > > function (and also it's more compact) > > > > > > > > I wonder if this is just a more extreme case of the logic in whatever > > > > check necessitated that I add an extra "return 0" at the very end of the > > > > function. (that happens even in gcc 6.x; at an earlier point when the > > > > function was simpler, that wasn't needed, but after some additions it > > > > started producing the "control reaches end of function that requires a > > > > return value" or whatever that warning is, and the only way to eliminate > > > > it was with the extra return 0.) > > > > > > > > If adding the break shuts up the warning, then I guess ACK, but it would > > > > probably be better if 1) gcc fixed their incorrect warning, or 2) we > > > > switched the entire function to use the less-compact "ret = blah; > > > > break;" style instead of returning directly, so there wasn't a single > > > > stray break sitting in the middle. > > > > > > > > > > I would say NACK since 1) is the correct option (at least for now), > > > there is no reason for adding more lines of code that don't make sense > > > just because of a compiler version that was not released yet, or does > > > not even have a release plan yet. > > > > GCC 7 *is* released - and has even had a bug fix release too, so ignoring > > this is not an option. In any case, as Eric mentions this is a genuine > > bug in our code since we can fall out of the inner switch if the input > > variable contains a value that doesn't map to an named enum value. > > > > Where did you get the package/tarball? I don't see anything in the > release page [1]. On the other hand, when I checked it yesterday, I > looked and the development timeline [2] and I thought it's 2016 > apparently because when I see the dates now it makes sense that the > release should be around the corner. Anyway, even if they did not > update the release page, on snapshot ftp [3] there is not even a release > candidate. I didn't use any tarball - just what's in Fedora which is gcc-7.0.1-0.9.fc26.x86_64 Fedora dist-git says the tarball is gcc-7.0.1-20170219.tar.bz2 Odd that its not on the download page though as that's a clearly a release version number, not a git snapshot or pre-release version.

> I remember others not being happy when we were doing workarounds for > packages that downstream distros just decided to package out of VCS or > snapshots. I don't feel it's right either and I thought you're on that > side as well. Anyway, if it really was released, I am OK with this > going in. Regardless of whether its a release or pre-release, this is a clear bug in the code that needs fixing - its just not a workaround for a compiler. As such I've pushed this series.

Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :| -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list