On Thu, 3 Aug 2017 10:34:45 -0300 Philippe Mathieu-Daudé <f4...@amsat.org> wrote:
> Hi Greg,
>
> On 08/02/2017 11:47 AM, Greg Kurz wrote:
> > Building QEMU on fedora26 with the latest gcc package fails:
> >
> > CC ppc64-softmmu/target/ppc/kvm.o
> > In file included from include/sysemu/hw_accel.h:16:0,
> > from target/ppc/kvm.c:31:
> > target/ppc/kvm.c: In function ‘kvmppc_booke_watchdog_enable’:
> > include/sysemu/kvm.h:449:35: error: ‘args_tmp[i]’ may be used uninitialized
> > in this function [-Werror=maybe-uninitialized]
> > cap.args[i] = args_tmp[i]; \
> > ^
> > target/ppc/kvm.c: In function ‘kvmppc_set_papr’:
> > include/sysemu/kvm.h:449:35: error: ‘args_tmp[i]’ may be used uninitialized
> > in this function [-Werror=maybe-uninitialized]
> > cc1: all warnings being treated as errors
> >
> > $ rpm -q gcc
> > gcc-7.1.1-3.fc26.ppc64le
> >
> > Testing the size of args_tmp seems to be enough to prevent the warning
> > to pop up.
>
> This sizeof() use looks unnatural to me. I wonder why not use size_t,
> since this is about sizeof()/ARRAY_SIZE(). The problem seems to come
> from the commit this cast was introduced (61c7bbd236):
>
> target-ppc/kvm.c:1302:21: error: comparison of unsigned expression < 0
> is always false [-Werror=type-limits]
>
Switching from int to size_t causes this error ^^ to show up again.
> So I'd rather suggest this code, which looks more natural to read to me:
>
> if (ARRAY_SIZE(args_tmp)) {
Yeah, it's maybe more in phase with the context but anyway, the truly
unnatural thing is to be forced to do:
if (foo) {
for (i = 0; i < foo; ...
> for (i = 0; i < ARRAY_SIZE(args_tmp) && ...
>
> I Cc'ed Eric :)
>
> Regards,
>
> Phil.
>
> >
> > Signed-off-by: Greg Kurz <gr...@kaod.org>
> > ---
> > include/sysemu/kvm.h | 12 ++++++++----
> > 1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
> > index 91fc07ee9afe..41fc1005a9ea 100644
> > --- a/include/sysemu/kvm.h
> > +++ b/include/sysemu/kvm.h
> > @@ -429,9 +429,11 @@ int kvm_vm_check_extension(KVMState *s, unsigned int
> > extension);
> > }; \
> > uint64_t args_tmp[] = { __VA_ARGS__ }; \
> > int i; \
> > - for (i = 0; i < (int)ARRAY_SIZE(args_tmp) && \
> > + if (sizeof(args_tmp)) { \
> > + for (i = 0; i < (int)ARRAY_SIZE(args_tmp) && \
> > i < ARRAY_SIZE(cap.args); i++) { \
> > - cap.args[i] = args_tmp[i]; \
> > + cap.args[i] = args_tmp[i]; \
> > + } \
> > } \
> > kvm_vm_ioctl(s, KVM_ENABLE_CAP, &cap); \
> > })
> > @@ -444,9 +446,11 @@ int kvm_vm_check_extension(KVMState *s, unsigned int
> > extension);
> > }; \
> > uint64_t args_tmp[] = { __VA_ARGS__ }; \
> > int i; \
> > - for (i = 0; i < (int)ARRAY_SIZE(args_tmp) && \
> > + if (sizeof(args_tmp)) { \
> > + for (i = 0; i < (int)ARRAY_SIZE(args_tmp) && \
> > i < ARRAY_SIZE(cap.args); i++) { \
> > - cap.args[i] = args_tmp[i]; \
> > + cap.args[i] = args_tmp[i]; \
> > + } \
> > } \
> > kvm_vcpu_ioctl(cpu, KVM_ENABLE_CAP, &cap); \
> > })
> >
> >
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