[Bug libstdc++/85951] make_signed and make_unsigned are incorrect for wchar_t, char16_t, and char32_t

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85951

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Thu May 31 12:18:19 2018
New Revision: 261023

URL: https://gcc.gnu.org/viewcvs?rev=261023&root=gcc&view=rev
Log:
PR libstdc++/85951 for make_signed/make_unsigned for character types

Because the wide character types are neither signed integer types nor
unsigned integer types they need to be transformed to an integral type
of the correct size and the lowest rank (which is not necessarily the
underlying type). Reuse the helpers for enumeration types to select the
correct integer.

The refactoring of __make_unsigned_selector and __make_signed_selector
slightly reduces the number of template instantiations and so reduces
memory usage.

        PR libstdc++/85951
        * include/std/type_traits [_GLIBCXX_USE_C99_STDINT_TR1]: Do not define
        uint_least16_t and uint_least32_t.
        (__make_unsigned<wchar_t>): Define unconditionally.
        (__make_unsigned_selector<_Tp, true, false>): Remove intermediate
        typedefs.
        (__make_unsigned_selector_base): New type to provide helper templates.
        (__make_unsigned_selector<_Tp, false, true>): Reimplement using
        __make_unsigned_selector_base helpers.
        (__make_unsigned<char16_t>, __make_unsigned<char32_t>): Define.
        (__make_signed_selector<_Tp, true, false>): Remove intermediate
        typedefs.
        (__make_signed<wchar_t>, __make_signed<char16_t>)
        (__make_signed<char32_t>)): Define unconditionally.
        * testsuite/20_util/make_signed/requirements/typedefs-3.cc: Check
        wchar_t, char16_t and char32_t are transformed correctly.
        * testsuite/20_util/make_signed/requirements/typedefs_neg.cc: Adjust
        dg-error lineno.
        * testsuite/20_util/make_unsigned/requirements/typedefs-3.cc: Check
        wchar_t, char16_t and char32_t are transformed correctly.
        * testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc: Adjust
        dg-error lineno.

Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/std/type_traits
    trunk/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs-3.cc
   
trunk/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc
   
trunk/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs-3.cc
   
trunk/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc