Re: [PATCH v5 06/21] perf arm-spe: Refactor printing string to buffer

[Leo Yan]

Hi Andre,

On Thu, Oct 29, 2020 at 10:23:39AM +0000, André Przywara wrote:

[...]

> > +static int arm_spe_pkt_snprintf(int *err, char **buf_p, size_t *blen,
> > +                           const char *fmt, ...)
> > +{
> > +   va_list ap;
> > +   int ret;
> > +
> > +   va_start(ap, fmt);
> > +   ret = vsnprintf(*buf_p, *blen, fmt, ap);
> > +   va_end(ap);
> > +
> > +   if (ret < 0) {
> > +           if (err && !*err)
> > +                   *err = ret;
> > +   } else {
> > +           *buf_p += ret;
> > +           *blen -= ret;
> > +   }
> > +
> > +   return ret;
> > +}
> 
> So this now implements the old behaviour of ignoring previous errors, in
> all cases, since we don't check for errors and bail out in the callers.
> 
> If you simply check for validity of err and for it being 0 before
> proceeding with the va_start() above, this should be fixed.

I think you are suggesting below code, could you take a look for it
before I proceed to respin new patch?

static int arm_spe_pkt_snprintf(int *err, char **buf_p, size_t *blen,
                                const char *fmt, ...)
{
        va_list ap;
        int ret;

        /* Bail out if any error occurred */
        if (err && *err)
                return *err;

        va_start(ap, fmt);
        ret = vsnprintf(*buf_p, *blen, fmt, ap);
        va_end(ap);

        if (ret < 0) {
                if (err && !*err)
                        *err = ret;
        } else {
                *buf_p += ret;
                *blen -= ret;
        }

        return ret;
}

Thanks,
Leo