Re: [libvirt] [PATCH] examples: If parameters count is zero we have nothing to do

On 06.07.2016 15:47, Marc Hartmayer wrote: > The virDomainGetCPUStats() API contract permits nparams == > 0. print_cpu_usage() assumes nparams > 0 because the domtop example > application isn't very useful if there are no statistics. Explicitly > error out to avoid potentially using the local variable pos > uninitialized. > > Reviewed-by: Boris Fiuczynski <fiuczy(a)linux.vnet.ibm.com&gt; > Reviewed-by: Sascha Silbe <silbe(a)linux.vnet.ibm.com&gt; > Reviewed-by: Bjoern Walk <bwalk(a)linux.vnet.ibm.com&gt; > Signed-off-by: Marc Hartmayer <mhartmay(a)linux.vnet.ibm.com&gt; > --- > examples/domtop/domtop.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/examples/domtop/domtop.c b/examples/domtop/domtop.c > index 2283994..f8e250b 100644 > --- a/examples/domtop/domtop.c > +++ b/examples/domtop/domtop.c > @@ -203,6 +203,11 @@ print_cpu_usage(const char *dom_name, > size_t nparams = now_nparams; > bool delim = false; > > + if (nparams == 0) { > + ERROR("parameter count is zero"); > + return; > + } > + > if (then_nparams != now_nparams) { > /* this should not happen (TM) */ > ERROR("parameters counts don't match"); > Not that I dislike this patch, but I fail to see how can @pos be used uninitialized if @nparams == 0. I mean, if @nparams == 0 and control gets to line 221 where @j is set to 0. Since the condition is false, the loop body is never executed leaving @pos unset. But, right after the loop, there's check 'if (j == nparams)', which appears like true to me, so and error is printed out and control jumps out from the function. Or am I missing something?