Re: [ft-devel] Undefined behavior

[Alexei Podtelezhnikov]

On Fri, Aug 8, 2014 at 4:56 PM, Behdad Esfahbod <address@hidden> wrote:
>
>     * src/base/ftcalc.c (FT_MSB): Utilize gcc builtins.
>
> introduced undefined behavior, since __builtin_clz and __builtin_ctz have
> undefined behavior if passed in value is zero.
>
> This can actually happen with degenerate glyph outlines.  It might be
> harmless, but it's something that should be fixed.

There is just a handful of places where FT_MSB is used.
* ftoutln.c, FT_MSB is used for scaling and you cannot really
scale/shift 0 unsafely or undefinedly.
* fttrigon.c, the same reasoning applies
* ftbbox.c, the same reasoning applies
* src/pfr/pfrobjs.c, do you think count can be 0 here?