fatal error: 'charconv' file not found in clang 6.0 with -std=c++17

Question

Recently, I wanted to use from_chars from c++17. Looked at http://en.cppreference.com/w/cpp/utility/from_chars and found that code on this page:

#include <iostream>
#include <charconv>
#include <array>

int main()
{
    std::array<char, 10> str{"42"};
    int result;
    std::from_chars(str.data(), str.data()+str.size(), result);
    std::cout << result;
}

cannot be compiled by any of compilers. I tried on page http://en.cppreference.com/w/cpp/utility/from_chars and on godbolt with different compilers but all of them returned the same error:

<source>:2:10: fatal error: 'charconv' file not found
#include <charconv>
         ^~~~~~~~~~
1 error generated.
Compiler returned: 1

Can anybody help me with this, please?

(I tried clang 6.0, gcc 7.3 and msvc 19 but all of them returned error that 'charconv' not found)

Answer 1

According to GCC's libstdc++ status page, this header is only supported starting from GCC-8.1. You could either avoid using this header by detecting it:

#if __has_include(<charconv>)
#include <charconv>
#else
/* implement some fallback */
#endif

Or just update your compiler. This godbolt example confirms that the header is present in GCC-8.1.

If you use Clang, remember that Clang uses GCC's stdlibc++ by default. You will either need to update your GCC or switch to Clang's libc++ by:

clang++ -std=c++17 -stdlib=libc++ main.cpp