On Fri, Sep 22, 2017 at 05:05:03PM +0100, Ramsay Jones wrote: > > As an aside, I also see some uses of hexval() that don't appear to be > > quite as rigorous in checking for invalid characters. A few > > unconditionally shift the first nibble and assume that there will still > > be high bits set. I think that's generally true for twos-complement > > negative numbers, but isn't shifting off the left side of a signed > > integer undefined behavior? > > All uses of hexval() that I can see are shifting an unsigned value. > Have I missed something?
Hmm. get_hex_color() does: unsigned int val; val = (hexval(in[0]) << 4) | hexval(in[1])); Isn't that shifting the signed return value of hexval(), and then converting it to unsigned afterwards? I've been confused by C's integer conversion rules before, though, so perhaps I'm wrong. I think if this function is fed an empty string that it will also read past the end of the buffer for in[1]. It shouldn't matter, since the NUL in in[0] would cause us to return an error regardless, but it's still undefined behavior. In fact, this whole function is just hex2chr() implemented badly. Who is responsible for this terrible code? ;) -Peff
