[PATCH 0/4]: C++ P1423R3 char8_t remediation implementation

Jonathan Wakely jwakely@redhat.com
Sat Nov 30 01:03:00 GMT 2019

On 29/11/19 21:45 +0000, Jonathan Wakely wrote:
>On 29/11/19 19:48 +0000, Jonathan Wakely wrote:
>>On 29/11/19 17:45 +0000, Jonathan Wakely wrote:
>>>On 15/09/19 15:39 -0400, Tom Honermann wrote:
>>>>This series of patches provides an implementation of the changes 
>>>>for C++ proposal P1423R3 [1].
>>>>These changes do not impact default libstdc++ behavior for C++17 
>>>>and earlier; they are only active for C++2a or when the 
>>>>-fchar8_t option is specified.
>>>>Tested x86_64-linux.
>>>>Patch 1: Decouple constraints for u8path from path constructors.
>>>>Patch 2: Update __cpp_lib_char8_t feature test macro value, add 
>>>>deleted operators, update u8path.
>>>>Patch 3: Updates to existing tests.
>>>>Patch 4: New tests.
>>>>[1]: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1423r3.html
>>>It took a while, but I've committed these four patches, with just some
>>>minor whitespace changes and changelog tweaks.
>>Running the new tests revealed a latent bug on Windows, where
>>experimental::filesystem::u8path(const Source&) assumed the input
>>was an iterator over a NTCTS. That worked for a const char* but not a
>>std::string or experimental::string_view.
>>The attached patch fixes that (and simplifies the #if and if-constexpr
>>conditions for Windows) but there's a remaining bug. Constructing a
>>experimental::filesystem::path from a char8_t string doesn't do the
>>right thing on Windows, so these cases fails:
>>fs::path p(u8"\xf0\x9d\x84\x9e");
>>VERIFY( p.u8string() == u8"\U0001D11E" );
>>p = fs::u8path(u8"\xf0\x9d\x84\x9e");
>>VERIFY( p.u8string() == u8"\U0001D11E" );
>>It works correctly for std::filesystem::path, just not the TS version.
>I think this is the fix needed for the TS code:
>--- a/libstdc++-v3/include/experimental/bits/fs_path.h
>+++ b/libstdc++-v3/include/experimental/bits/fs_path.h
>@@ -765,7 +765,14 @@ namespace __detail
>      {
>       if constexpr (is_same<_CharT, char8_t>::value)
>-         return _S_wconvert((const char*)__f, (const char*)__l, true_type());
>+         {
>+           const char* __f2 = (const char*)__f;
>+           const char* __l2 = (const char*)__l;
>+           std::wstring __wstr;
>+           std::codecvt_utf8_utf16<wchar_t> __wcvt;
>+           if (__str_codecvt_in_all(__f2, __l2, __wstr, __wcvt))
>+             return __wstr;
>+         }
>       else
>         {
>The current code uses std::codecvt<wchar_t, char, mbstate_t> but when
>we know the input is UTF-8 encoded we should use codecvt_utf8_utf16
>(which is what the C++17 code already does for char8_t input).
>I'll add that the patch I'm testing.

Here's the final patch I'm committing. Tested powerpc64le-linux and
x86_64-w64-mingw, committed to trunk.

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