Re: [PATCH] exec: Remove the duplicated check in parse_cpu_option()

[Greg Kurz]

On Sat, 7 Dec 2019 23:56:55 +1100
Gavin Shan <address@hidden> wrote:

> On 12/7/19 3:58 AM, Greg Kurz wrote:
> > On Fri,  6 Dec 2019 17:33:37 +1100
> > Gavin Shan <address@hidden> wrote:
> > 
> >> The @cpu_option shouldn't be NULL, otherwise assertion from g_strsplit()
> >> should be raised as below message indicates. So it's meaningless to 
> >> validate
> >> @model_pices[0] in parse_cpu_option() as it shouldn't be NULL either.
> >>
> >>     qemu-system-aarch64: GLib: g_strsplit: assertion 'string != NULL' 
> >> failed
> >>
> >> This just removes the check and unused message.
> >>
> > 
> > Hrm... the check isn't about @cpu_option being NULL. It is about filtering 
> > out
> > invalid syntaxes like:
> > 
> > -cpu ''
> > 
> > or
> > 
> > -cpu ,some-prop
> > 
> 
> Greg, Thanks for your review on this trivial patch.
> 
> @cpu_option[0] is NULL when we have "-cpu ''". We run into assertion raised
> by subsequent cpu_class_by_name(). However, @cpu_option[0] isn't NULL with
> something like "-cpu ,xxx", but the CPU model specific class can't be found
> at last.
> 

You're right, the case with a leading ',' is caught by the other check.

> So the validation mostly relies on cpu_class_by_name() if I'm correct. It's
> fine to remove the check. However, it provides explicit error message, which
> isn't bad though:
> 
>     error_report("-cpu option cannot be empty");
> 

It's definitely not fine to remove an error message that clearly explains
to the user what he has done wrong in favor of QEMU aborting and printing
something cryptic like:

    cpu_class_by_name: Assertion `cpu_model && cc->class_by_name' failed.

Assertions are for bugs, not for bad command line usage.

> >> Signed-off-by: Gavin Shan <address@hidden>
> >> ---
> >>   exec.c | 5 -----
> >>   1 file changed, 5 deletions(-)
> >>
> >> diff --git a/exec.c b/exec.c
> >> index ffdb518535..3cff459e43 100644
> >> --- a/exec.c
> >> +++ b/exec.c
> >> @@ -963,11 +963,6 @@ const char *parse_cpu_option(const char *cpu_option)
> >>       const char *cpu_type;
> >>   
> >>       model_pieces = g_strsplit(cpu_option, ",", 2);
> >> -    if (!model_pieces[0]) {
> >> -        error_report("-cpu option cannot be empty");
> >> -        exit(1);
> >> -    }
> >> -
> >>       oc = cpu_class_by_name(CPU_RESOLVING_TYPE, model_pieces[0]);
> >>       if (oc == NULL) {
> >>           error_report("unable to find CPU model '%s'", model_pieces[0]);
> > 
> 
> Regards,
> Gavin
> 

Cheers,

--
Greg