https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101794
Bug ID: 101794
Summary: std::lerp with NaN input does not result in NaN
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: jonas.rahlf.basf at gmail dot com
Target Milestone: ---
>From the description of std::lerp I would have expected that providing NaN as t
would result in NaN, but it does not.
The return value should be "a+t(b−a)" so if t==NaN then the result should also
be NaN.
Example:
#include <limits>
#include <cmath>
#include <iostream>
int main()
{
constexpr float nan = std::numeric_limits<float>::quiet_NaN();
float result = std::lerp(1, 2, nan);
std::cout << result << std::endl; // outputs 2
}
Yields 2, see https://godbolt.org/z/do4zEhs5o .
Compile with g++ -std=c++20.
With clang you also get 2, but with MSVC you get NaN.
