[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches
On Thu, Jan 24, 2019 at 4:44 AM Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote: > > On Wed, 23 Jan 2019, Edwin Zimmerman <edwin@xxxxxxxxxxxxxxxxx> wrote: > > On Wed, 23 Jan 2019, Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote: > >> On Wed, 23 Jan 2019, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > >> > On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote: > >> >> Variables declared in a switch statement before any case statements > >> >> cannot be initialized, so move all instances out of the switches. > >> >> After this, future always-initialized stack variables will work > >> >> and not throw warnings like this: > >> >> > >> >> fs/fcntl.c: In function ‘send_sigio_to_task’: > >> >> fs/fcntl.c:738:13: warning: statement will never be executed > >> >> [-Wswitch-unreachable] > >> >> siginfo_t si; > >> >> ^~ > >> > > >> > That's a pain, so this means we can't have any new variables in { } > >> > scope except for at the top of a function? Just in case this wasn't clear: no, it's just the switch statement before the first "case". I cannot imagine how bad it would be if we couldn't have block-scoped variables! Heh. :) > >> > > >> > That's going to be a hard thing to keep from happening over time, as > >> > this is valid C :( > >> > >> Not all valid C is meant to be used! ;) > > > > Very true. The other thing to keep in mind is the burden of enforcing > > a prohibition on a valid C construct like this. It seems to me that > > patch reviewers and maintainers have enough to do without forcing them > > to watch for variable declarations in switch statements. Automating > > this prohibition, should it be accepted, seems like a good idea to me. > > Considering that the treewide diffstat to fix this is: > > 18 files changed, 45 insertions(+), 46 deletions(-) > > and using the gcc plugin in question will trigger the switch-unreachable > warning, I think we're good. There'll probably be the occasional > declarations that pass through, and will get fixed afterwards. Yeah, that was my thinking as well: it's a rare use, and we get a warning when it comes up. Thanks! -- Kees Cook _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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