[libcxx] [test] Fix the monetary locale negative_sign test for en_US.UTF-8 on Windows

[mstorsjo]

Summary

On Windows, the en_US.UTF-8 locale returns n_sign_posn == 0, which
means that the sign for a negative currency is parentheses around
the whole value, instead of a leading minus.

[mstorsjo]

Simplify the patch significantly, fixing building in configurations without wchar available.

[• Quuxplusone]

Seems fine to me. My only suggestion is that I imagine there must be other tests that need updating in the same way for actually formatting negative numbers, like

        Fwt f(LOCALE_en_US_UTF_8, 1);
#if defined(_WIN32)
        assert(f.whateverformatmoney(-42) == L"(42)");
#else
        assert(f.whateverformatmoney(-42) == L"-42");
#endif

and maybe you could hit those tests in this same PR?

[mstorsjo]

In D120549#3345680, @Quuxplusone wrote:

Seems fine to me. My only suggestion is that I imagine there must be other tests that need updating in the same way for actually formatting negative numbers, like

        Fwt f(LOCALE_en_US_UTF_8, 1);
#if defined(_WIN32)
        assert(f.whateverformatmoney(-42) == L"(42)");
#else
        assert(f.whateverformatmoney(-42) == L"-42");
#endif

and maybe you could hit those tests in this same PR?

Yes, there’s actually a bunch of them. Unfortunately, some of them require a whole lot of churn in the tests, so I’m a bit undecided about some of them, whether it’s worth to fix them, or just change the XFAIL to a non-FIXME version, with an explanation. But this one seemed tolerable enough at least.

libcxx/test/std/localization/locale.categories/category.monetary/locale.moneypunct.byname/negative_sign.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // REQUIRES: locale.en_US.UTF-8
 // REQUIRES: locale.fr_FR.UTF-8
 // REQUIRES: locale.ru_RU.UTF-8
 // REQUIRES: locale.zh_CN.UTF-8
 
-// XFAIL: LIBCXX-WINDOWS-FIXME
-
 // <locale>
 
 // class moneypunct_byname<charT, International>
 
 // string_type negative_sign() const;
 
 #include <locale>
 #include <limits>
#ifndef TEST_HAS_NO_WIDE_CHARACTERS
     {
         Fwt f("C", 1);
         assert(f.negative_sign() == std::wstring());
     }
 #endif
 
     {
         Fnf f(LOCALE_en_US_UTF_8, 1);
+#if defined(_WIN32)
+        assert(f.negative_sign() == "()");
+#else
         assert(f.negative_sign() == "-");
+#endif
     }
     {
         Fnt f(LOCALE_en_US_UTF_8, 1);
+#if defined(_WIN32)
+        assert(f.negative_sign() == "()");
+#else
         assert(f.negative_sign() == "-");
+#endif
     }
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
     {
         Fwf f(LOCALE_en_US_UTF_8, 1);
+#if defined(_WIN32)
+        assert(f.negative_sign() == L"()");
+#else
         assert(f.negative_sign() == L"-");
+#endif
     }
     {
         Fwt f(LOCALE_en_US_UTF_8, 1);
+#if defined(_WIN32)
+        assert(f.negative_sign() == L"()");
+#else
         assert(f.negative_sign() == L"-");
+#endif
     }
 #endif
 
     {
         Fnf f(LOCALE_fr_FR_UTF_8, 1);
         assert(f.negative_sign() == "-");
     }
     {