Re: [qemu-s390x] [PATCH 17/17] checkpatch: Warn when errp is passed to error_append_hint()

[Greg Kurz]

On Tue, 17 Sep 2019 13:29:36 +0200
Cornelia Huck <address@hidden> wrote:

> On Tue, 17 Sep 2019 12:22:18 +0200
> Greg Kurz <address@hidden> wrote:
> 
> > Passing errp from the argument list to error_append_hint()
> > isn't recommended because it may cause unwanted behaviours
> > when errp is equal to &error_fatal or &error_abort.
> > 
> > First, error_append_hint() aborts QEMU when passed either of
> > those.
> > 
> > Second, consider the following:
> > 
> >     void foo(Error **errp)
> >     {
> >          error_setg(errp, "foo");
> >          error_append_hint(errp, "Try bar\n");
> >     }
> > 
> > error_setg() causes QEMU to exit or abort, and hints aren't
> > added.
> > 
> > Signed-off-by: Greg Kurz <address@hidden>
> > ---
> >  scripts/checkpatch.pl |    4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> > index aa9a354a0e7e..17ce026282a6 100755
> > --- a/scripts/checkpatch.pl
> > +++ b/scripts/checkpatch.pl
> > @@ -2902,6 +2902,10 @@ sub process {
> >             }
> >     }
> >  
> 
> Maybe add a comment here?
> 
> # using errp is common practice, so that check should hopefully be enough
> 
> > +           if ($line =~ /error_append_hint\(errp/) {
> > +               WARN("suspicious errp passed to error_append_hint()\n" .
> 
> Add "(use a local error object)"?
> 

Sure. I'll add both.

> > +                    $herecurr);
> > +           }
> >  # check for non-portable libc calls that have portable alternatives in QEMU
> >             if ($line =~ /\bffs\(/) {
> >                     ERROR("use ctz32() instead of ffs()\n" . $herecurr);
> > 
>