This needs some changes since the code may not work on all platforms. On Wed, Sep 17, 2014 at 10:06 AM, Neil Roberts <n...@linux.intel.com> wrote:
> Actually I think this might be a slightly cleaner way to do the shift > because it doesn't depend on any particular size of unsigned int and > there are fewer ~s. > > - Neil > > ------- >8 --------------- (use git am --scissors to automatically chop > here) > > The un_to_float function was trying to get the maximum value given a > number of bits by shifting ~0ul by the number of bits. For the > GL_UNSIGNED_INT type this function was also being used to get a > maximum value for a 32-bit quantity. However on a 32-bit build this > would mean that it is shifting a 32-bit integer (unsigned long is > 32-bit) by 32 bits. The C spec leaves it undefined what happens if you > do a shift that is greater than the number of bits in the type. GCC > takes advantage of that to make the shift a no-op so the maximum was > ending up as zero and the test fails. > > This patch makes it shift ~0u in the other direction so that it > doesn't matter what size unsigned int is and it won't try to shift by > 32. > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=83695 > --- > tests/texturing/teximage-colors.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tests/texturing/teximage-colors.c > b/tests/texturing/teximage-colors.c > index 815ef4d..0afb4b1 100644 > --- a/tests/texturing/teximage-colors.c > +++ b/tests/texturing/teximage-colors.c > @@ -189,7 +189,7 @@ valid_combination(GLenum format, GLenum type) > static float > un_to_float(unsigned char bits, unsigned int color) > { > - unsigned int max = ~(~0ul << bits); > + unsigned int max = ~0u >> (sizeof max * 8 - bits); > why not use, sizeof(unsigned int)? the call "sizeof max" may not always work depending on compiler > return (float)color / (float)max; > } > > -- > 1.9.3 > > _______________________________________________ > Piglit mailing list > Piglit@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/piglit >
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