My colleague was doing some basic experiments with NaN and was puzzled by the behavior on Visual Studio that did not match his expectations. After discussion, it seems that he uncovered a probable compiler bug in MSVC 2019.
This code snippet fails to compile on MSVC, but is fine on Clang and GCC:
#include <limits>
int main()
{
static_assert(!(1 < std::numeric_limits<double>::quiet_NaN()), "compiler bug?");
}
Demo: https://godbolt.org/z/xGdqd5
Il seems that the problem concerns compile-time comparison of a constant with std::numeric_limits<double>::quiet_NaN(), something not really useful in real life.
The comparison > and < is always false if quiet_NaN is compared with a variable as expected by IEEE-754.