Refactor <locale> RAII guards to aid upcoming Windows locale changes.

Previously <locale> used std::unique_ptr<remove_ptr<locale_t>, locale-mgmt-function>
as a scope guard for (A) creating new locales, and (B) setting the thread specific locale
in RAII safe manner.

However using unique_ptr has some problems, first it requires that locale_t is a pointer
type, which may not be the case (Windows will need a non-pointer locale_t type that emulates _locale_t).

The second problem is that users of the guards had to supply the locale management function to the custom
deleter at every call site. However these locale management functions don't exist natively Windows, making
a good Windows implementation of locale more difficult.

This patch creates distinct and simply RAII guards that replace unique_ptr. These guards handle calling
the correct locale management function so that callers don't have too. This simplification will
aid in upcoming Windows fixes.

llvm-svn: 302474

1 files changed, 19 insertions, 0 deletions

diff --git a/libcxx/include/__locale b/libcxx/include/__locale
index 4184e7e0348..cf3ba23b909 100644
--- a/libcxx/include/__locale
+++ b/libcxx/include/__locale
@@ -49,6 +49,25 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+#if !defined(_LIBCPP_LOCALE__L_EXTENSIONS) || defined(_LIBCPP_MSVCRT)
+struct __libcpp_locale_guard {
+  _LIBCPP_INLINE_VISIBILITY
+  __libcpp_locale_guard(locale_t& __loc) : __old_loc_(uselocale(__loc)) {}
+
+  _LIBCPP_INLINE_VISIBILITY
+  ~__libcpp_locale_guard() {
+    if (__old_loc_)
+      uselocale(__old_loc_);
+  }
+
+  locale_t __old_loc_;
+private:
+  __libcpp_locale_guard(__libcpp_locale_guard const&);
+  __libcpp_locale_guard& operator=(__libcpp_locale_guard const&);
+};
+#endif
+
+
 class _LIBCPP_TYPE_VIS locale;
 
 template <class _Facet>