Re: [Cake] [PATCH] q_cake: Update xstats format to use per-tin structure

["Luis E. Garcia" <luis@bitamins.net>]

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Nice work Kevin.

On Sat, Mar 10, 2018 at 09:56 Kevin Darbyshire-Bryant <
kevin@darbyshire-bryant.me.uk> wrote:

>
>
> > On 8 Mar 2018, at 11:21, Toke Høiland-Jørgensen <toke@toke.dk> wrote:
> >
> >>
> >> Oh and curiously the bad values go away if you ask for json output
> >> it’s much better.  Which rather points at a ‘feature’ of the
> >> ‘print_string’ behaviour.
> >
> > Right. Well, the print_* functions are behind several levels of
> > pre-processor indirection, so not quite obvious what's going on here.
> > Don't really see why they should spit out garbage values, though.
> >
> >
> > Stephen, do you have any ideas?
> >
> > -Toke
>
> Right, cracked it and it’s horrible!
>
> print_uint is expanded thus:  Note the type of value uint64_t
>
>               void print_color_uint(enum output_type t, enum color_attr
> color, const char *key, const char *fmt, uint64_t value);
> static inline void print_uint      (enum output_type t,
>     const char *key, const char *fmt, uint64_t value)
>                  { print_color_uint(                 t, COLOR_NONE,
>                 key,             fmt,          value); };
>
> So far so good.
>
> print_color_uint expands to:
>
>              void print_color_uint(enum output_type t, enum color_attr
> color, const char *key, const char *fmt, uint64_t value)
>  {
>   if (((t & PRINT_JSON || t & PRINT_ANY) && _jw))
>     { if (!key) jsonw_uint(_jw, value);
>       else      jsonw_uint_field(_jw, key, value);
>     }
>   else if ((!_jw && (t & PRINT_FP || t & PRINT_ANY)))
>     { color_fprintf( (stdout) , color, fmt, value);
>     }
>  };
>
> Again, no issue and we eventually call color_fprintf
>
> int color_fprintf(FILE *fp, enum color_attr attr, const char *fmt, ...)
> {
>         int ret = 0;
>         va_list args;
>
>         va_start(args, fmt);
>
>         if (!color_is_enabled || attr == COLOR_NONE) {
>                 ret = vfprintf(fp, fmt, args);
>                 goto end;
>         }
>
>
> Now, color_printf is a variable argument list function and as such is
> dependent upon being told the correct size of argument variables in the fmt
> variable.  And that’s our problem, we’re passing a 64bit integer but
> telling the format string that it’s ‘int’…which I’m guessing can be
> variable sizes depending on architecture, as can the endianness.
>
> If we instead do (in q_cake.c)
>
> #include <inttypes.h>
>
> print_uint(PRINT_ANY, "min_transport_size", " min/max transport layer
> size: %10" PRIu64, stnc->min_trnlen);
>
> it works.  This needs sanity checking by a clever person.
>
> Cheers,
>
> Kevin D-B
>
> 012C ACB2 28C6 C53E 9775  9123 B3A2 389B 9DE2 334A
>
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