[Bug libstdc++/64276] New: would be better to use __cpp_exceptions rather than __EXCEPTIONS to determine whether exceptions are available

[richard-gccbugzilla at metafoo dot co.uk]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64276

            Bug ID: 64276
           Summary: would be better to use __cpp_exceptions rather than
                    __EXCEPTIONS to determine whether exceptions are
                    available
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: richard-gccbugzilla at metafoo dot co.uk
                CC: redi at gcc dot gnu.org

libstdc++ uses __EXCEPTIONS to determine wither exceptions are available, and
uses __GXX_RTTI to determine if RTTI is available. __EXCEPTIONS is ambiguous;
it can mean either "generate cleanups on exception unwind paths" or "allow C++
exception handling syntax", and some compilers allow these flags to be set
independently. It would be more portable (and would set a better example) to
use __cpp_exceptions and __cpp_rtti rather than these macros, now that GCC
supports them.