[Bug c++/64497] New: std::scalbln does not round correctly for long doubles

[walter.mascarenhas at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64497

            Bug ID: 64497
           Summary: std::scalbln does not round correctly for long doubles
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: walter.mascarenhas at gmail dot com

The overload std::scalbln(long double, long) may not round the result correctly
when the exponent is very small. For instance, with round mode = near,

    std::scalbln(1.1L, -16446) 

returns 0, whereas  std::scalbn(1.1L, -16446) and std::ldexp(1.1L, -16446)
return std::numeric_limits<long double>::denorm_min(), which I believe
is the correct result.