CODEWITHSUNDEEP
c++visual-c++
mce16
mce16

Reputation: 21

Compile issue with MSVC std::isfinite

Hi the following codes won't compile in MSCV; it gives error

(9): error C3615: constexpr function 'Test' cannot result in a constant expression due to the use of std::isfinite!? 
constexpr int Test(double value)
{
    if (!std::isfinite((double)value))
    {
        return 1;
    }

    return 0;
}

//}

gcc is fine, how to fix it?

Upvotes: 0

Views: 282

Answers (1)

Adrian McCarthy
Adrian McCarthy

Reputation: 48022

std::isfinite isn't marked as constexpr until C++23. Apparently gcc's standard library has already implemented this feature and MSVC's hasn't yet.

Make sure, when you compile with MSVC, to ask for the latest version of the standard with /std:c++latest. But I'm guessing they just haven't made that change yet.

In the meantime, you could write your own implementation of isfinite that is constexpr. I think the Wikipedia page on IEEE floating point has enough detail to come up with the appropriate test condition. I think the infinities and NaN values have all bits of the exponent field set to 1.

Upvotes: 1

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