First of all, the redo of the iterator portion in response to https://gcc.gnu.org/ml/gcc-patches/2019-11/msg01467.html passed testing.
This patch contains constexpr char_traits. I also found an old extension that had been left out of the constexpr bandwagon that I caught up.
This patch also includes constexpr string_view::copy which depends on teh type_traits.
This gets all of p1032 except string::copy (although constexpr char_traits should almost enable this too once constexpr string is in). I'm done.
This passes on x86_64-linux. OK?
2019-11-16 Edward Smith-Rowland <3dw...@verizon.net> Implement the char_traits and string_view part of C++20 p1032 Misc. constexpr bits. * include/bits/char_traits.h (move, copy, assign): Constexpr. * include/bits/stl_algobase.h (__memcpy, __memset): New. * include/ext/pod_char_traits.h (from, to, operator==, operator<) (assign, eq, lt, compare, length, find, move, copy, assign) (to_char_type, to_int_type, eq_int_type, eof, not_eof): Make these constespr for appropriate standards. * testsuite/21_strings/char_traits/requirements/char/constexpr.cc: New test. * testsuite/21_strings/char_traits/requirements/wchar_t/constexpr.cc: New test. * include/std/string_view (copy): Constexpr. * testsuite/21_strings/basic_string_view/operations/copy/char/constexpr.cc: New test. * testsuite/21_strings/basic_string_view/operations/copy/wchar_t/constexpr.cc: New test.
Index: include/bits/char_traits.h =================================================================== --- include/bits/char_traits.h (revision 278318) +++ include/bits/char_traits.h (working copy) @@ -113,13 +113,13 @@ static _GLIBCXX14_CONSTEXPR const char_type* find(const char_type* __s, std::size_t __n, const char_type& __a); - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* move(char_type* __s1, const char_type* __s2, std::size_t __n); - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* copy(char_type* __s1, const char_type* __s2, std::size_t __n); - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* assign(char_type* __s, std::size_t __n, char_type __a); static _GLIBCXX_CONSTEXPR char_type @@ -179,18 +179,17 @@ } template<typename _CharT> - typename char_traits<_CharT>::char_type* + _GLIBCXX20_CONSTEXPR typename char_traits<_CharT>::char_type* char_traits<_CharT>:: move(char_type* __s1, const char_type* __s2, std::size_t __n) { if (__n == 0) return __s1; - return static_cast<_CharT*>(__builtin_memmove(__s1, __s2, - __n * sizeof(char_type))); + return static_cast<_CharT*>(std::__memmove<true>(__s1, __s2, __n)); } template<typename _CharT> - typename char_traits<_CharT>::char_type* + _GLIBCXX20_CONSTEXPR typename char_traits<_CharT>::char_type* char_traits<_CharT>:: copy(char_type* __s1, const char_type* __s2, std::size_t __n) { @@ -200,7 +199,7 @@ } template<typename _CharT> - typename char_traits<_CharT>::char_type* + _GLIBCXX20_CONSTEXPR typename char_traits<_CharT>::char_type* char_traits<_CharT>:: assign(char_type* __s, std::size_t __n, char_type __a) { @@ -349,28 +348,28 @@ return static_cast<const char_type*>(__builtin_memchr(__s, __a, __n)); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* move(char_type* __s1, const char_type* __s2, size_t __n) { if (__n == 0) return __s1; - return static_cast<char_type*>(__builtin_memmove(__s1, __s2, __n)); + return static_cast<char_type*>(std::__memmove<true>(__s1, __s2, __n)); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) { if (__n == 0) return __s1; - return static_cast<char_type*>(__builtin_memcpy(__s1, __s2, __n)); + return static_cast<char_type*>(std::__memcpy(__s1, __s2, __n)); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* assign(char_type* __s, size_t __n, char_type __a) { if (__n == 0) return __s; - return static_cast<char_type*>(__builtin_memset(__s, __a, __n)); + return static_cast<char_type*>(std::__memset(__s, __a, __n)); } static _GLIBCXX_CONSTEXPR char_type @@ -458,27 +457,42 @@ return wmemchr(__s, __a, __n); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* move(char_type* __s1, const char_type* __s2, size_t __n) { if (__n == 0) return __s1; +#ifdef __cpp_lib_is_constant_evaluated + if (std::is_constant_evaluated()) + return static_cast<char_type*>(std::__memmove<true>(__s1, __s2, __n)); + else +#endif return wmemmove(__s1, __s2, __n); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) { if (__n == 0) return __s1; +#ifdef __cpp_lib_is_constant_evaluated + if (std::is_constant_evaluated()) + return static_cast<char_type*>(std::__memcpy(__s1, __s2, __n)); + else +#endif return wmemcpy(__s1, __s2, __n); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* assign(char_type* __s, size_t __n, char_type __a) { if (__n == 0) return __s; +#ifdef __cpp_lib_is_constant_evaluated + if (std::is_constant_evaluated()) + return static_cast<char_type*>(std::__memset(__s, __a, __n)); + else +#endif return wmemset(__s, __a, __n); } @@ -567,28 +581,28 @@ return static_cast<const char_type*>(__builtin_memchr(__s, __a, __n)); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* move(char_type* __s1, const char_type* __s2, size_t __n) { if (__n == 0) return __s1; - return static_cast<char_type*>(__builtin_memmove(__s1, __s2, __n)); + return static_cast<char_type*>(std::__memmove<true>(__s1, __s2, __n)); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) { if (__n == 0) return __s1; - return static_cast<char_type*>(__builtin_memcpy(__s1, __s2, __n)); + return static_cast<char_type*>(std::__memcpy(__s1, __s2, __n)); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* assign(char_type* __s, size_t __n, char_type __a) { if (__n == 0) return __s; - return static_cast<char_type*>(__builtin_memset(__s, __a, __n)); + return static_cast<char_type*>(std::__memset(__s, __a, __n)); } static _GLIBCXX_CONSTEXPR char_type @@ -680,25 +694,23 @@ return 0; } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* move(char_type* __s1, const char_type* __s2, size_t __n) { if (__n == 0) return __s1; - return (static_cast<char_type*> - (__builtin_memmove(__s1, __s2, __n * sizeof(char_type)))); + return static_cast<char_type*>(std::__memmove<true>(__s1, __s2, __n)); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) { if (__n == 0) return __s1; - return (static_cast<char_type*> - (__builtin_memcpy(__s1, __s2, __n * sizeof(char_type)))); + return static_cast<char_type*>(std::__memcpy(__s1, __s2, __n)); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* assign(char_type* __s, size_t __n, char_type __a) { for (size_t __i = 0; __i < __n; ++__i) @@ -783,25 +795,23 @@ return 0; } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* move(char_type* __s1, const char_type* __s2, size_t __n) { if (__n == 0) return __s1; - return (static_cast<char_type*> - (__builtin_memmove(__s1, __s2, __n * sizeof(char_type)))); + return (static_cast<char_type*>(std::__memmove<true>(__s1, __s2, __n))); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) { if (__n == 0) return __s1; - return (static_cast<char_type*> - (__builtin_memcpy(__s1, __s2, __n * sizeof(char_type)))); + return (static_cast<char_type*>(std::__memcpy(__s1, __s2, __n))); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* assign(char_type* __s, size_t __n, char_type __a) { for (size_t __i = 0; __i < __n; ++__i) Index: include/bits/stl_algobase.h =================================================================== --- include/bits/stl_algobase.h (revision 278318) +++ include/bits/stl_algobase.h (working copy) @@ -107,6 +107,50 @@ } /* + * A constexpr wrapper for __builtin_memmove. + * @param __num The number of elements of type _Tp (not bytes). + */ + template<typename _Tp> + _GLIBCXX14_CONSTEXPR + inline void* + __memcpy(_Tp* __dst, const _Tp* __src, size_t __num) + { +#ifdef __cpp_lib_is_constant_evaluated + if (std::is_constant_evaluated()) + { + for(; __num > 0; --__num) + *__dst++ = *__src++; + return __dst; + } + else +#endif + return __builtin_memcpy(__dst, __src, sizeof(_Tp) * __num); + return __dst; + } + + /* + * A constexpr wrapper for __builtin_memmove. + * @param __num The number of elements of type _Tp (not bytes). + */ + template<typename _Tp> + _GLIBCXX14_CONSTEXPR + inline void* + __memset(_Tp* __dst, _Tp __a, size_t __num) + { +#ifdef __cpp_lib_is_constant_evaluated + if (std::is_constant_evaluated()) + { + for(; __num > 0; --__num) + *__dst = __a; + return __dst; + } + else +#endif + return __builtin_memset(__dst, __a, sizeof(_Tp) * __num); + return __dst; + } + + /* * A constexpr wrapper for __builtin_memcmp. * @param __num The number of elements of type _Tp (not bytes). */ Index: include/ext/pod_char_traits.h =================================================================== --- include/ext/pod_char_traits.h (revision 278318) +++ include/ext/pod_char_traits.h (working copy) @@ -56,7 +56,7 @@ value_type value; template<typename V2> - static char_type + static _GLIBCXX_CONSTEXPR char_type from(const V2& v) { char_type ret = { static_cast<value_type>(v) }; @@ -64,7 +64,7 @@ } template<typename V2> - static V2 + static _GLIBCXX_CONSTEXPR V2 to(const char_type& c) { V2 ret = { static_cast<V2>(c.value) }; @@ -74,13 +74,13 @@ }; template<typename _Value, typename _Int, typename _St> - inline bool + inline _GLIBCXX_CONSTEXPR bool operator==(const character<_Value, _Int, _St>& lhs, const character<_Value, _Int, _St>& rhs) { return lhs.value == rhs.value; } template<typename _Value, typename _Int, typename _St> - inline bool + inline _GLIBCXX_CONSTEXPR bool operator<(const character<_Value, _Int, _St>& lhs, const character<_Value, _Int, _St>& rhs) { return lhs.value < rhs.value; } @@ -102,19 +102,19 @@ typedef fpos<state_type> pos_type; typedef streamoff off_type; - static void + static _GLIBCXX14_CONSTEXPR void assign(char_type& __c1, const char_type& __c2) { __c1 = __c2; } - static bool + static _GLIBCXX_CONSTEXPR bool eq(const char_type& __c1, const char_type& __c2) { return __c1 == __c2; } - static bool + static _GLIBCXX_CONSTEXPR bool lt(const char_type& __c1, const char_type& __c2) { return __c1 < __c2; } - static int + static _GLIBCXX14_CONSTEXPR int compare(const char_type* __s1, const char_type* __s2, size_t __n) { for (size_t __i = 0; __i < __n; ++__i) @@ -123,7 +123,7 @@ return 0; } - static size_t + static _GLIBCXX14_CONSTEXPR size_t length(const char_type* __s) { const char_type* __p = __s; @@ -132,7 +132,7 @@ return (__p - __s); } - static const char_type* + static _GLIBCXX14_CONSTEXPR const char_type* find(const char_type* __s, size_t __n, const char_type& __a) { for (const char_type* __p = __s; size_t(__p - __s) < __n; ++__p) @@ -141,7 +141,7 @@ return 0; } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* move(char_type* __s1, const char_type* __s2, size_t __n) { if (__n == 0) @@ -150,7 +150,7 @@ (__builtin_memmove(__s1, __s2, __n * sizeof(char_type))); } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) { if (__n == 0) @@ -159,7 +159,7 @@ return __s1; } - static char_type* + static _GLIBCXX20_CONSTEXPR char_type* assign(char_type* __s, size_t __n, char_type __a) { std::fill_n(__s, __n, __a); @@ -166,19 +166,19 @@ return __s; } - static char_type + static _GLIBCXX_CONSTEXPR char_type to_char_type(const int_type& __i) { return char_type::template from(__i); } - static int_type + static _GLIBCXX_CONSTEXPR int_type to_int_type(const char_type& __c) { return char_type::template to<int_type>(__c); } - static bool + static _GLIBCXX_CONSTEXPR bool eq_int_type(const int_type& __c1, const int_type& __c2) { return __c1 == __c2; } - static int_type + static _GLIBCXX_CONSTEXPR int_type eof() { int_type __r = { static_cast<typename __gnu_cxx::__conditional_type @@ -187,7 +187,7 @@ return __r; } - static int_type + static _GLIBCXX_CONSTEXPR int_type not_eof(const int_type& __c) { return eq_int_type(__c, eof()) ? int_type() : __c; } }; Index: testsuite/21_strings/char_traits/requirements/char/constexpr.cc =================================================================== --- testsuite/21_strings/char_traits/requirements/char/constexpr.cc (nonexistent) +++ testsuite/21_strings/char_traits/requirements/char/constexpr.cc (working copy) @@ -0,0 +1,42 @@ +// { dg-options "-std=gnu++2a" } +// { dg-do compile { target c++2a } } +// +// Copyright (C) 2019 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// <http://www.gnu.org/licenses/>. + +#include <string> + +constexpr bool +test() +{ + auto ok = true; + + char casv[8]{"ello, W"}; + + char das[8]{}; + std::char_traits<char>::move(das, casv, 7); + std::char_traits<char>::copy(das, casv, 7); + std::char_traits<char>::assign(das, 7, 'x'); + + return ok; +} + +int +main() +{ + static_assert(test()); +} Index: testsuite/21_strings/char_traits/requirements/wchar_t/constexpr.cc =================================================================== --- testsuite/21_strings/char_traits/requirements/wchar_t/constexpr.cc (nonexistent) +++ testsuite/21_strings/char_traits/requirements/wchar_t/constexpr.cc (working copy) @@ -0,0 +1,42 @@ +// { dg-options "-std=gnu++2a" } +// { dg-do compile { target c++2a } } +// +// Copyright (C) 2019 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// <http://www.gnu.org/licenses/>. + +#include <string> + +constexpr bool +test() +{ + auto ok = true; + + wchar_t cawsv[8]{L"ello, W"}; + + wchar_t wdas[8]{}; + std::char_traits<wchar_t>::move(wdas, cawsv, 7); + std::char_traits<wchar_t>::copy(wdas, cawsv, 7); + std::char_traits<wchar_t>::assign(wdas, 7, L'x'); + + return ok; +} + +int +main() +{ + static_assert(test()); +} Index: include/std/string_view =================================================================== --- include/std/string_view (revision 278318) +++ include/std/string_view (working copy) @@ -252,6 +252,7 @@ // [string.view.ops], string operations: + _GLIBCXX20_CONSTEXPR size_type copy(_CharT* __str, size_type __n, size_type __pos = 0) const { Index: testsuite/21_strings/basic_string_view/operations/copy/char/constexpr.cc =================================================================== --- testsuite/21_strings/basic_string_view/operations/copy/char/constexpr.cc (nonexistent) +++ testsuite/21_strings/basic_string_view/operations/copy/char/constexpr.cc (working copy) @@ -0,0 +1,37 @@ +// { dg-options "-std=gnu++2a" } +// { dg-do compile { target c++2a } } +// +// Copyright (C) 2019 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. +// +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. +// +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// <http://www.gnu.org/licenses/>. + +#include <string_view> + +constexpr bool +test_string_view() +{ + auto ok = true; + + constexpr std::string_view sv = "Hello, World!!!"; + char casv[8]{}; + sv.copy(casv, 7, 1); + + ok = ok && (casv[0] == 'e'); + + return ok; +} + +static_assert(test_string_view()); Index: testsuite/21_strings/basic_string_view/operations/copy/wchar_t/constexpr.cc =================================================================== --- testsuite/21_strings/basic_string_view/operations/copy/wchar_t/constexpr.cc (nonexistent) +++ testsuite/21_strings/basic_string_view/operations/copy/wchar_t/constexpr.cc (working copy) @@ -0,0 +1,37 @@ +// { dg-options "-std=gnu++2a" } +// { dg-do compile { target c++2a } } +// +// Copyright (C) 2019 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. +// +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. +// +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// <http://www.gnu.org/licenses/>. + +#include <string_view> + +constexpr bool +test_string_view() +{ + auto ok = true; + + constexpr std::wstring_view wsv = L"Hello, World!!!"; + wchar_t cawsv[8]{}; + wsv.copy(cawsv, 7, 1); + + ok = ok && (cawsv[0] == L'e'); + + return ok; +} + +static_assert(test_string_view());