[Bug libgcc/86742] New: Documented function std::to_chars(char* first, char* last, double value) is not implemented

[j.wink...@fu-berlin.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86742

            Bug ID: 86742
           Summary: Documented function std::to_chars(char* first, char*
                    last, double value) is not implemented
           Product: gcc
           Version: 8.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libgcc
          Assignee: unassigned at gcc dot gnu.org
          Reporter: j.wink...@fu-berlin.de
  Target Milestone: ---

In cppreference (https://en.cppreference.com/w/cpp/utility/to_chars) there is a
function std::to_chars documented that should work also for floating point
types. 

If I modify the given example to pass a double 42.0 instead of int 42 to the
function, the compiler gives the following error, contradicting the
documentation: 

g++-8 -std=c++17 examplefile.cpp

error: no matching function for call to 'to_chars(std::array<char,
10>::pointer, std::array<char, 10>::pointer, double)'
     if(auto [p, ec] = std::to_chars(str.data(), str.data() + str.size(),
42.0);