On 15/11/16 14:33 +0000, Jonathan Wakely wrote:
This is another issue resolution for C++17 features that was approved at the recent meeting. I think this resolution is wrong too, but in this case the fix is obvious so I've gone ahead and done it.* doc/xml/manual/intro.xml: Document LWG 2742 status. * doc/html/*: Regenerate. * include/bits/basic_string.h (basic_string(const T&, size_type, size_type, const Allocator&)): Add constructor for substring of basic_string_view, as per LWG 2742 but with additional constraint to fix ambiguity. * testsuite/21_strings/basic_string/cons/char/9.cc: New test. * testsuite/21_strings/basic_string/cons/wchar_t/9.cc: New test. Tested powerpc64le-linux, comitted to trunk.
I forgot I already added an convenience alias template for checking the condition in this patch. Tested powerpc64le-linux, comitted to trunk.
commit f7852de7c77f0d9cc8520d10549da0652e334dc7 Author: Jonathan Wakely <[email protected]> Date: Tue Nov 15 18:55:35 2016 +0000 Use existing helper for new std::string constructor * include/bits/basic_string.h: Reuse _If_sv alias template for new constructor. diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h index 943e88d..9af7bfb 100644 --- a/libstdc++-v3/include/bits/basic_string.h +++ b/libstdc++-v3/include/bits/basic_string.h @@ -585,6 +585,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 { _M_construct(__beg, __end); } #if __cplusplus > 201402L + template<typename _Tp, typename _Res> + using _If_sv = enable_if_t< + __and_<is_convertible<const _Tp&, __sv_type>, + __not_<is_convertible<const _Tp&, const _CharT*>>>::value, + _Res>; + /** * @brief Construct string from a substring of a string_view. * @param __t Source string view. @@ -592,9 +598,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 * @param __n The number of characters to copy from __t. * @param __a Allocator to use. */ - template<typename _Tp, typename = - _Require<is_convertible<_Tp, __sv_type>, - __not_<is_convertible<const _Tp&, const _CharT*>>>> + template<typename _Tp, typename = _If_sv<_Tp, void>> basic_string(const _Tp& __t, size_type __pos, size_type __n, const _Alloc& __a = _Alloc()) : basic_string(__sv_type(__t).substr(__pos, __n), __a) { } @@ -1252,12 +1256,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 append(__sv_type __sv) { return this->append(__sv.data(), __sv.size()); } - template<typename _Tp, typename _Res> - using _If_sv = enable_if_t< - __and_<is_convertible<const _Tp&, __sv_type>, - __not_<is_convertible<const _Tp&, const _CharT*>>>::value, - _Res>; - /** * @brief Append a range of characters from a string_view. * @param __sv The string_view to be appended from.
