Re: Alexandre Julliard : gdi32: Avoid overflows for invalid coordinates in line clipping.

[Charles Davis]

On Feb 22, 2012, at 1:27 PM, Alexandre Julliard wrote:
> --- a/dlls/gdi32/dibdrv/objects.c
> +++ b/dlls/gdi32/dibdrv/objects.c
> @@ -372,7 +372,8 @@ static inline DWORD calc_outcode(const POINT *pt, const RECT *clip)
> int clip_line(const POINT *start, const POINT *end, const RECT *clip,
>               const bres_params *params, POINT *pt1, POINT *pt2)
> {
> - int m, n;
> -
> - INT64 m, n;  /* 64-bit to avoid overflows (FIXME: find a more efficient way) */

What about MulDiv()? As I recall, this is the sort of situation for which it was designed. Or is that not efficient?

Chip

Alexandre Julliard : gdi32: Avoid overflows for invalid coordinates in line clipping.

[Alexandre Julliard]

Charles Davis  writes:
> On Feb 22, 2012, at 1:27 PM, Alexandre Julliard wrote:
> > --- a/dlls/gdi32/dibdrv/objects.c
> > +++ b/dlls/gdi32/dibdrv/objects.c
> > @@ -372,7 +372,8 @@ static inline DWORD calc_outcode(const POINT *pt, const RECT *clip)
> > int clip_line(const POINT *start, const POINT *end, const RECT *clip,
> >               const bres_params *params, POINT *pt1, POINT *pt2)
> > {
> > - int m, n;
> > -
> > - INT64 m, n;  /* 64-bit to avoid overflows (FIXME: find a more efficient way) */
> What about MulDiv()? As I recall, this is the sort of situation for
> which it was designed. Or is that not efficient?

It could possibly be made to work, but MulDiv's rounding is different,
and adding the bias would be more complicated.