Re: [Qemu-devel] [PULL v2 0/9] bitmap export over NBD

[Eric Blake]

On 06/22/2018 07:13 AM, Peter Maydell wrote:
> On 22 June 2018 at 13:12, Eric Blake <address@hidden> wrote:
> > Uurgh. It's a false positive (the compiler is complaining that the variable
> > is uninitialized, which can only happen if the while loop is not executed;
> > but the preconditions guarantee the loop executes at least once).  The
> > assert() that I added was enough to silence gcc 7.3.1 on my Fedora 27
> > system, but address@hidden is using gcc-8.1.1-1.fc28.x86_64. This
> > should silence things (another way to silence would be rewriting while{}
> > into do{}while).  I'll submit this as a formal patch if I can reproduce the
> > problem/fix on docker.
>
> Huh. I had thought this was an old-gcc problem, not a new-gcc
> one. Might be worth submitting to the gcc folks as a regression...

Hmm, I couldn't quickly reproduce it with a direct gcc on Fedora 28; and 
I don't know docker well enough to know if the cross-gcc used in 
address@hidden is a different version than the native gcc-8.1.1 
listed in the installed packages list (the patchew output doesn't list 
the version of x86_64-w64-mingw32-gcc). Thus, I can't tell if it is a 
recent gcc regression or merely an old-gcc issue.  But I can confirm 
that 'make address@hidden' reproduced the problem without my 
cleanup patch, and that my cleanup patch now in master made that happy 
again.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org