[libc++] Support multibyte decimal_point and thousands_sep

[vangyzen]

Summary

numpunct_byname<wchar_t> assumed that decimal_point and thousands_sep
were ASCII and simply copied the first byte from them. Add support
for multibyte strings in these fields.

I found this problem on FreeBSD 11, where thousands_sep in fr_FR.UTF-8
is a no-break space (U+00A0).

[vangyzen]

A unit test change in D26979 found this and will continue to test it (on some OSes).

[EricWF]

Huh, I thought I had already fixed this but apparently I forgot to commit the patch. You can find my fix here: https://reviews.llvm.org/D24218

[vangyzen]

I'm abandoning this revision because D24218 is clearly superior.

src/locale.cpp

 {
     __init(nm.c_str());
 }
 
 numpunct_byname<wchar_t>::~numpunct_byname()
 {
 }
 
+#if defined(__clang__)
+#pragma clang diagnostic ignored "-Wmissing-braces"
+#endif
+
 void
 numpunct_byname<wchar_t>::__init(const char* nm)
 {
     if (strcmp(nm, "C") != 0)
     {
         __locale_unique_ptr loc(newlocale(LC_ALL_MASK, nm, 0), freelocale);
         if (loc == nullptr)
-            __throw_runtime_error("numpunct_byname<char>::numpunct_byname"
+            __throw_runtime_error("numpunct_byname<wchar_t>::numpunct_byname"
                                   " failed to construct for " + string(nm));
 
         lconv* lc = __libcpp_localeconv_l(loc.get());
-        if (*lc->decimal_point)
-            __decimal_point_ = *lc->decimal_point;
-        if (*lc->thousands_sep)
-            __thousands_sep_ = *lc->thousands_sep;
+        if (*lc->decimal_point) {
+            size_t len = strlen(lc->decimal_point);
+            mbstate_t mbs = {0};
+            wchar_t wc;
+            size_t nb = __libcpp_mbrtowc_l(&wc, lc->decimal_point, len, &mbs,
+                loc.get());
+            if (nb == len) {
+                __decimal_point_ = wc;
+            } else {
+                __throw_runtime_error("numpunct_byname<wchar_t>: decimal_point"
+                                      " is not a valid multibyte character: " +
+                                      string(lc->decimal_point));
+            }
+        }
+        if (*lc->thousands_sep) {
+            size_t len = strlen(lc->thousands_sep);
+            mbstate_t mbs = {0};
+            wchar_t wc;
+            size_t nb = __libcpp_mbrtowc_l(&wc, lc->thousands_sep, len, &mbs,
+                loc.get());
+            if (nb == len) {
+                __thousands_sep_ = wc;
+            } else {
+                __throw_runtime_error("numpunct_byname<wchar_t>: thousands_sep"
+                                      " is not a valid multibyte character: " +
+                                      string(lc->thousands_sep));
+            }
+        }
         __grouping_ = lc->grouping;
-        // locallization for truename and falsename is not available
+        // localization for truename and falsename is not available
     }
 }
 
 // num_get helpers
 
 int
 __num_get_base::__get_base(ios_base& iob)
 {
while (bb != be)
             continue;
         }
         result.push_back(*bb);
         ++bb;
     }
     return result;
 }
 
-#if defined(__clang__)
-#pragma clang diagnostic ignored "-Wmissing-braces"
-#endif
-
 template <>
 wstring
 __time_get_storage<wchar_t>::__analyze(char fmt, const ctype<wchar_t>& ct)
 {
     tm t = {0};
     t.tm_sec = 59;
     t.tm_min = 55;
     t.tm_hour = 23;