[Bug c++/107097] New: Implement floating point excess precision in C++

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107097

            Bug ID: 107097
           Summary: Implement floating point excess precision in C++
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jason at gcc dot gnu.org
  Target Milestone: ---

Joseph Myers implemented C99 excess precision support for C in 4.5:
https://gcc.gnu.org/legacy-ml/gcc-patches/2008-11/msg00105.html

C++ has a similar rule in [expr.pre]p6:

"The values of the floating-point operands and the results of floating-point
expressions may be represented in greater precision and range than that
required by the type; the types are not changed thereby. [Footnote: The cast
and assignment operators must still perform their specific conversions.]"

Implementing this seems particularly important for users wanting to use 16-bit
floating point types in C++.