[Patch, libstdc++/64649] Fix regex_traits::lookup_collatename and regex_traits::lookup_classname

[Jonathan Wakely]

On 19/01/15 18:01 -0800, Tim Shen wrote:
>    	PR libstdc++/64649
>    	* include/bits/regex.tcc (regex_traits<>::lookup_collatename,
>    	regex_traits<>::lookup_classname): Correctly narrow input chars.
>    	* testsuite/28_regex/traits/wchar_t/user_defined.cc: New testcase.

OK for trunk, as this is actually fixing a regression (we did narrow
the input range before the last patch for this bug).

>--- a/libstdc++-v3/testsuite/28_regex/traits/wchar_t/user_defined.cc
>+++ b/libstdc++-v3/testsuite/28_regex/traits/wchar_t/user_defined.cc
>@@ -55,8 +55,32 @@ test01()
>   VERIFY(!regex_match(L"\u2029", re));
> }
>
>+struct MyCtype : std::ctype<wchar_t>
>+{
>+  char
>+  do_narrow(wchar_t c, char dflt) const override
>+  {
>+    if (c >= 256)
>+      return dflt;
>+    return ((char)c)+1;
>+  }
>+};
>+
>+void
>+test02()
>+{
>+  std::locale loc(std::locale(), new MyCtype);
>+  std::regex_traits<wchar_t> traits;
>+  traits.imbue(loc);
>+  wchar_t wch = L'p';
>+  VERIFY(traits.lookup_collatename(&wch, &wch+1) == L"q");
>+  std::wstring ws = L"`kog`"; // chars of "alpha" shifted by 1.

Could this use "digit" instead of "alpha" so it shifts to "chfhs"
instead of something with non-alphabetic characters?