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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r11-4590] libstdc++: Define type traits for wchar_t even when libc support missing Date: Sun, 1 Nov 2020 11:39:22 +0000 (GMT) [thread overview] Message-ID: <20201101113922.93BA23851C18@sourceware.org> (raw) https://gcc.gnu.org/g:29e418485848c4a6943d8561cd8fb0b1abf14015 commit r11-4590-g29e418485848c4a6943d8561cd8fb0b1abf14015 Author: Jonathan Wakely <jwakely@redhat.com> Date: Sun Nov 1 10:56:36 2020 +0000 libstdc++: Define type traits for wchar_t even when libc support missing This meets the requirement that std::is_integral_v<wchar_t> is true, even when full library support for wchar_t via specializations of char_traits etc. is not provided. This is done by checking __WCHAR_TYPE__ to see if the compiler knows about the type, rather than checking the library's own _GLIBCXX_USE_WCHAR_T autoconf macro. This assumes that the C++ compiler correctly defines wchar_t as a distinct type, not a typedef for one of the other integeral types. This is always true for G++ and should be true for any supported non-GNU compilers. Similarly, the std::make_unsigned and std::make_signed traits and the internal helpers std::__is_integer and std::__is_char are also changed to depend on the same macro. libstdc++-v3/ChangeLog: * include/std/type_traits (is_integral<wchar_t>) (make_unsigned<wchar_t>, make_signed<wchar_t>): Define based on #ifdef __WCHAR_TYPE__ instead of _GLIBCXX_USE_WCHAR_T. * include/bits/cpp_type_traits.h (__is_integer<wchar_t>) (__is_char<wchar_t>): Likewise. Diff: --- libstdc++-v3/include/bits/cpp_type_traits.h | 4 ++-- libstdc++-v3/include/std/type_traits | 9 ++++++--- 2 files changed, 8 insertions(+), 5 deletions(-) diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h b/libstdc++-v3/include/bits/cpp_type_traits.h index b48d1adc63c..433a2d7d35b 100644 --- a/libstdc++-v3/include/bits/cpp_type_traits.h +++ b/libstdc++-v3/include/bits/cpp_type_traits.h @@ -162,7 +162,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION typedef __true_type __type; }; -# ifdef _GLIBCXX_USE_WCHAR_T +# ifdef __WCHAR_TYPE__ template<> struct __is_integer<wchar_t> { @@ -363,7 +363,7 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3) typedef __true_type __type; }; -#ifdef _GLIBCXX_USE_WCHAR_T +#ifdef __WCHAR_TYPE__ template<> struct __is_char<wchar_t> { diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits index e9a0f55dd4a..34e068b5952 100644 --- a/libstdc++-v3/include/std/type_traits +++ b/libstdc++-v3/include/std/type_traits @@ -269,7 +269,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION struct __is_integral_helper<unsigned char> : public true_type { }; -#ifdef _GLIBCXX_USE_WCHAR_T + // We want is_integral<wchar_t> to be true (and make_signed/unsigned to work) + // even when libc doesn't provide working <wchar.h> and related functions, + // so check __WCHAR_TYPE__ instead of _GLIBCXX_USE_WCHAR_T. +#ifdef __WCHAR_TYPE__ template<> struct __is_integral_helper<wchar_t> : public true_type { }; @@ -1742,7 +1745,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // neither signed integer types nor unsigned integer types, so must be // transformed to the unsigned integer type with the smallest rank. // Use the partial specialization for enumeration types to do that. -#if defined(_GLIBCXX_USE_WCHAR_T) +#ifdef __WCHAR_TYPE__ template<> struct __make_unsigned<wchar_t> { @@ -1868,7 +1871,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // signed integer types nor unsigned integer types, so must be // transformed to the signed integer type with the smallest rank. // Use the partial specialization for enumeration types to do that. -#if defined(_GLIBCXX_USE_WCHAR_T) +#if defined(__WCHAR_TYPE__) template<> struct __make_signed<wchar_t> {
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