[PATCH v8 11/11] lib: sbi: Fix missing '\0' when buffer szie equal 1

[Anup Patel]

On Thu, Jul 6, 2023 at 12:20 PM Xiang W <wxjstz at 126.com> wrote:
>
> 在 2023-07-06星期四的 11:08 +0530，Anup Patel写道：
> > On Wed, Jul 5, 2023 at 8:08 PM Xiang W <wxjstz at 126.com> wrote:
> > >
> > > Fix special case: sbi_snprintf(out, out_len, ...) when out_len equal
> > > 1, The previous code will not fill the buffer with any char.
> >
> > I would rather do something like below in printc(...)
> >
> > diff --git a/lib/sbi/sbi_console.c b/lib/sbi/sbi_console.c
> > index 168dffd..e0ecb41 100644
> > --- a/lib/sbi/sbi_console.c
> > +++ b/lib/sbi/sbi_console.c
> > @@ -138,10 +138,10 @@ static void printc(char **out, u32 *out_len, char ch)
> >       * The *printf entry point functions have enforced that (*out) can
> >       * only be null when out_len is non-null and its value is zero.
> >       */
> > -    if (!out_len || *out_len > 1) {
> > +    if (!out_len || *out_len)
> >          *(*out)++ = ch;
> > +    if (!out_len || *out_len > 1)
> >          **out = '\0';
> > -    }
>
> When *out_len is equal to 1, that is, when there is not enough buffer to drop
> the formatted string, a string without '\0' will be generated.
>
> And when there is a problem with the format in sbi_snprintf, it may not entry
> printc at all. e.g:
>         sbi_printf(out,out_len,"%f",3.14)

Fair enough but I still think check on out_len is also required.

if (out && out_len && *out_len)
    **out = '\0';

Regards,
Anup

>
> Regards,
> Xiang W
>
> >
> >      if (out_len && *out_len > 0)
> >          --(*out_len);
> >
> > Regards,
> > Anup
> >
> > >
> > > Signed-off-by: Xiang W <wxjstz at 126.com>
> > > ---
> > >  lib/sbi/sbi_console.c | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > >
> > > diff --git a/lib/sbi/sbi_console.c b/lib/sbi/sbi_console.c
> > > index 00feec8..0703d4a 100644
> > > --- a/lib/sbi/sbi_console.c
> > > +++ b/lib/sbi/sbi_console.c
> > > @@ -271,6 +271,10 @@ static int print(char **out, u32 *out_len, const char *format, va_list args)
> > >                 out_len = &console_tbuf_len;
> > >         }
> > >
> > > +       /* handle special case: *out_len == 1*/
> > > +       if (out)
> > > +               **out = '\0';
> > > +
> > >         for (; *format != 0; ++format) {
> > >                 width = flags = 0;
> > >                 if (use_tbuf)
> > > --
> > > 2.40.1
> > >
>