Compile error when calling std::from_chars with a double in libc++

Asked Aug 05 '21 at 14:57

Active Aug 05 '21 at 15:37

Viewed 1,622 times

I have a small code as follows:

int main() {
    double d;
    const char* str = "26.50";
    std::from_chars(str, str + strlen(str), d);
    std::cout << d;
}

This code works as expected with libstdc++, but it fails with the following error in libc++ 12.0.0:

candidate template ignored: requirement '__or_<std::__or_<std::is_same<double, signed char>, std::is_same<double, short>, std::is_same<double, int>, std::is_same<double, long>, std::is_same<double, long long>>, std::__or_<std::is_same<double, unsigned char>, std::is_same<double, unsigned short>, std::is_same<double, unsigned int>, std::is_same<double, unsigned long>, std::is_same<double, unsigned long long>>, std::is_same<char, double>>::value' was not satisfied [with _Tp = double]

Is this a libc++ bug? or am I missing something? I should say that this code works if I change data type from double to int.

edited Aug 05 '21 at 15:37

Botje

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asked Aug 05 '21 at 14:57

Afshin

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I don't think they have implemented floating point support yet. Let me try and find the dupe target. – NathanOliver Aug 05 '21 at 14:58
Yep, https://en.cppreference.com/w/cpp/compiler_support confirms that. – HolyBlackCat Aug 05 '21 at 14:59
This is the best I'm finding: https://stackoverflow.com/questions/57825432/what-blocks-implementation-of-stdto-chars-and-stdfrom-chars – NathanOliver Aug 05 '21 at 15:01
@HolyBlackCat ouch. I didn't think they may have implemented main but not specializations... <.< Ty info. – Afshin Aug 05 '21 at 15:03
do you mean clang or libc++? Clang [compiles your code without errors](https://godbolt.org/z/o4fobjW7v) – Alan Birtles Aug 05 '21 at 15:06
@AlanBirtles: With libc++: https://godbolt.org/z/8nhM3Y3na – Bill Lynch Aug 05 '21 at 15:16
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@BillLynch, yes that was my point, the problem is libc++ not clang as originally stated in the question – Alan Birtles Aug 05 '21 at 15:20

Compile error when calling std::from_chars with a double in libc++

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