[committed 3/3] libstdc++: Refactor filesystem::path string conversions

Jonathan Wakely jwakely@redhat.com
Mon Jun 1 23:14:22 GMT 2020

On 23/05/20 09:44 +0100, Jonathan Wakely wrote:
>This simplifies the logic of converting Source arguments and pairs of
>InputIterator arguments into the native string format. For any input
>that is a contiguous range of path::value_type (or char8_t for POSIX)
>a string view can be created and the conversion can be done directly,
>with no intermediate allocation. Previously some cases created a
>basic_string unnecessarily, for example construction from a pair of
>path::string_type::iterators, or a pair of non-const value_type*
>        * include/bits/fs_path.h (__detail::_S_range_begin)
>        (__detail::_S_range_end, path::_S_string_from_iter): Replace with
>        overloaded function template __detail::__effective_range.
>        (__detail::__effective_range): New overloaded function template to
>        create a basic_string or basic_string_view for an effective range.
>        (__detail::__value_type_is_char): Use __detail::__effective_range.
>        Do not use remove_const on value type.
>        (__detail::__value_type_is_char_or_char8_t): Likewise.
>        (path::path(const Source&, format))
>        (path::path(const Source&, const locale&))
>        (path::operator/=(const Source&), path::append(const Source&))
>        (path::concat(const Source&)): Use __detail::__effective_range.
>        (path::_S_to_string(InputIterator, InputIterator)): New function
>        template to create a string view if possible, or string otherwise.
>        (path::_S_convert): Add overloads that convert a string returned
>        by __detail::__effective_range. Use if-constexpr to inline conversion
>        logic from all overloads of _Cvt::_S_convert.
>        (path::_S_convert_loc): Add overload that converts a string. Use
>        _S_to_string to avoid allocation when possible.
>        (path::_Cvt): Remove.
>        (path::operator+=(CharT)): Remove indirection through path::concat.
>        * include/experimental/bits/fs_path.h (path::_S_convert_loc): Add
>        overload for non-const pointers, to avoid constructing a std::string.
>        * src/c++17/fs_path.cc (path::_S_convert_loc): Replace conditional
>        compilation with call to _S_convert.

This commit broke *-*-mingw* bootstrap. Fixed with the attached patch.

Tested powerpc64le-linux and x86_64-w64-mingw32, committed to master.

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