Re: [Xen-devel] [PATCH V4 09/24] libxl_json: introduce parser functions for builtin types

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, May 06, 2014 at 03:35:27PM +0100, Anthony PERARD wrote:
[...]
> > +/* Macro to generate:
> > + *  libxl__uint8_parse_json
> > + *  libxl__uint16_parse_json
> > + *  libxl__uint32_parse_json
> > + *  libxl__uint64_parse_json
> > + */
> > +#define PARSE_UINT(width)                                               \
> > +    int libxl__uint ## width ## _parse_json(libxl__gc *gc,              \
> > +                                            const libxl__json_object *o,\
> > +                                            void *p)                    \
> > +    {                                                                   \
> > +        long long i;                                                    \
> > +                                                                        \
> > +        if (!libxl__json_object_is_integer(o))                          \
> > +            return ERROR_FAIL;                                          \
> > +                                                                        \
> > +        i = libxl__json_object_get_integer(o);                          \
> > +                                                                        \
> > +        if (i > UINT ## width ## _MAX)                                  \
> > +            return ERROR_FAIL;                                          \
> 
> My guest is this will always be false for uint64 and maybe for uint32.
> The value return by get_interger can only be <= LLONG_MAX which I
> suppose is still < UINT64_MAX.
> 

I was just being lazy about it.

> Also, 'i' might be < 0.
> 

Phew, I knew this but somehow I thought it was OK. :-(

So the two things combined, the check should be

   (i > 0 && i < UINT ## width ## _MAX)

What do you think?

> If json contain a value > LLONG_MAX, the value will be store as a string
> with the type number.
> 

This is also true, but I coded like this on purpose. You won't be able
to convert that string anyway because that's why it's stored as string
in the first place. We should just return ERROR_FAIL in this case, which
we do already with the check libxl__json_object_is_integer.

Wei.

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