[PATCH] ipa/rpi/controller: Use fabs for calculating absolute values

[Milan Zamazal]

Laurent Pinchart <laurent.pinchart at ideasonboard.com> writes:

> On Fri, Aug 16, 2024 at 03:40:45PM +0200, Milan Zamazal wrote:
>> Kieran Bingham <kieran.bingham at ideasonboard.com> writes:
>> 
>
>> > Hi Maarten,
>> >
>> > Thank you for highlighting this. I'm curious that it hasn't come up in
>> > our builds yet! What version of clang are you using?
>> 
>> It happens to me too, with clang 18.1.6 on Fedora 40.
>
> I'm very surprised, I tested with clang 18.1.8 locally and didn't see
> any error. I would have fixed it already otherwise :-)

Interesting.  I checked in another environment with clang 17.0.6 and it
also reports the error.  Can it perhaps depend on particular C/C++
header setup/version?  When I ask LSP about `abs' at the given place,
it points me to the following from stdlib.h:

  extern int abs (int __x) __THROW __attribute__ ((__const__)) __wur;

>> > Quoting Maarten Lankhorst (2024-08-15 10:37:15)
>> >> I was getting the following error in clang:
>> >> ../src/ipa/rpi/controller/rpi/awb.cpp:508:6: error: using integer absolute value function 'abs' when argument is of floating point type [-Werror,-Wabsolute-value]
>> >>         if (abs(denominator) > eps) {
>> >>             ^
>> >> ../src/ipa/rpi/controller/rpi/awb.cpp:508:6: note: use function 'std::abs' instead
>> >
>> > Is there a preference against the recommended std::abs?
>> >
>> >>         if (abs(denominator) > eps) {
>> >>             ^~~
>> >>             std::abs
>> >> 
>> >> Signed-off-by: Maarten Lankhorst <dev at lankhorst.se>
>> >> ---
>> >>  src/ipa/rpi/controller/rpi/awb.cpp | 2 +-
>> >>  1 file changed, 1 insertion(+), 1 deletion(-)
>> >> 
>> >> diff --git a/src/ipa/rpi/controller/rpi/awb.cpp b/src/ipa/rpi/controller/rpi/awb.cpp
>> >> index f45525bc..c5750c84 100644
>> >> --- a/src/ipa/rpi/controller/rpi/awb.cpp
>> >> +++ b/src/ipa/rpi/controller/rpi/awb.cpp
>> >> @@ -505,7 +505,7 @@ static double interpolateQuadatric(ipa::Pwl::Point const &a, ipa::Pwl::Point con
>> >>         const double eps = 1e-3;
>> >>         ipa::Pwl::Point ca = c - a, ba = b - a;
>> >>         double denominator = 2 * (ba.y() * ca.x() - ca.y() * ba.x());
>> >> -       if (abs(denominator) > eps) {
>> >> +       if (fabs(denominator) > eps) {
>> >>                 double numerator = ba.y() * ca.x() * ca.x() - ca.y() * ba.x() * ba.x();
>> >>                 double result = numerator / denominator + a.x();
>> >>                 return std::max(a.x(), std::min(c.x(), result));