Re: [Xen-devel] [PATCH v1 3/3] blktap2: Silence warnings under GCC 5.1.1

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.10.15 at 16:26, <konrad.wilk@xxxxxxxxxx> wrote:
> On Mon, Oct 05, 2015 at 04:46:55AM -0600, Jan Beulich wrote:
>> >>> On 05.10.15 at 10:49, <andrew.cooper3@xxxxxxxxxx> wrote:
>> > On 03/10/15 19:39, Konrad Rzeszutek Wilk wrote:
>> >> I get compile warnings telling me that
>> >>    s->connections[i].fd == fd
>> >>
>> >> 'i' may be past the array. Adding in an extra condition
>> >> on the loop fixes that.
>> >>
>> >> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
>> > 
>> > Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> > 
>> > Furthermore, I can't see any logic which prevents s->connected getting
>> > larger than MAX_CONNECTIONS
>> 
>> Iirc Olaf had already suggested such a patch quite some time ago,
>> and not having seen the point back then I also don't see the point
>> now: ctl_accept() prevents ->connected from growing beyond 1,
>> and there's no other place where the value could get incremented.
> 
> Thoughts on what to do about the compiler warnings which make this
> compiler errors (since we compile with -Werror) and one can't
> compile Xen? A different fix (make s->connected not be an array?)

To be honest I think this needs to be taken care of at the compiler
side, as I can't see any reason for the warning. The workaround
therefore would be to suppress the warning via -Wno-* until the
compiler side would get fixed. (Of course I'm open to be convinced
otherwise, i.e. this not being a compiler issue.)

>> Also, Konrad, regarding the subject (since this repeats from an
>> earlier patch of yours) - why do you reference a specific, non-
>> release version of gcc? Why not simply say 5.x? Because if the
>> problem is indeed only present in a non-release version, I don't
>> think we should bother working around such issues.
> 
> I just ran 'gcc --version' and that is what it spit out. Since
> it is part of an official Fedora release I figured it is 'released'
> in some way?

Well, if my understanding of gcc's new versioning is correct, only
<x>.<y>.<z> with y > 0 and z == 0 are released versions. 5.1.1
would be an RC for 5.2.0 (which already got released).

Jan


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