Re: thoughts on error passing, was Re: [PATCH 2/2] fsck: handle bad trees like other errors

[Jeff King <peff@peff.net>]

On Tue, Sep 27, 2016 at 06:57:34PM -0400, David Turner wrote:

> >   int report_error(struct error_context *err, const char *fmt, ...)
> >   {
> >         if (err->fn) {
> >                 va_list ap;
> >                 va_start(ap, fmt);
> >                 err->fn(err->data, fmt, ap);
> >                 va_end(ap);
> >         }
> >         return -1;
> >   }
> > 
> > Then low-level functions just take a context and do:
> > 
> >   return report_error(&err, "some error: %s", foo);
> > 
> > And then the callers would pick one of a few generic error contexts:
> > 
> >   - passing NULL silences the errors
> 
> Overall, +1.
> 
> I guess I would rather have a sentinel value for silencing errors,
> because I'm worried that someone might read NULL as "don't handle the
> errors, just die".  Of course, code review would hopefully catch this,
> but even so, it would be easier to read foo(x, y, silence_errors) than
> foo(x, y, null).

Yeah, I waffled on that. If you look carefully, you'll note that
the report_error() I showed above would actually require such a
"{ NULL, NULL }" global.

I don't plan to make any patches immediately for this, but I'll let it
percolate and consider whether it makes sense to try out for a future
series.

-Peff