Re: [pygame] 7 failures and 1 error in test suite

[René Dudfield <renesd@xxxxxxxxx>]

Cool, thanks for the testing.


On Thu, Jul 2, 2009 at 9:19 AM, Lorenz Quack<don@xxxxxxxxxxxxxxxxx> wrote:
> Ok, so here goes my analysis of the failures in ColorTypeTest:
> In src/color.c line 1435 (and some following lines) we bit shift each color
> component and stuff them
> in an unsigned long.

Maybe this should be into a uint32 instead?


> I think the problem arises when we bitshift the r value and r is >127
> My guess is that C converts r to an integer during the bitshift and not to
> an unsigned int so
> if r > 127 the integer (r is shifted by 24) overflows and becomes negative
> (note that the internal
> bit representation of the int has not changed) but when we store this
> (negative) integer into a
> long it remains negative so the first bits get filled up with "1"s.
> I see different solutions to this and cant decide which is the _correct_ one
> so I'll just present them
> instead:
>  1) don't save the combined color in an unsigned long. use a unsigned int
> instead.
>    This should work as long as r, g, b, a are UInt8 and aren't shifted more
> than 24
>  2) explicitly cast the r value to be unsigned
>  3) cast the r value to be (unsigned) long
>
> furthermore I think in the we should compare tmp to UINT_MAX in line 1438,
> 1476 and 1492.
> even though I haven't put much thought into this at least then the tests
> don't fail.
>