[libc++] std::ostream::sentry should excluded from explicit instantiation on client-side

Author: kikairoya

libcxx/docs/DesignDocs/VisibilityMacros.rst

@@ -93,6 +93,11 @@ Visibility Macros
   the extern template declaration) as exported on Windows, as discussed above.
   On all other platforms, this macro has an empty definition.
 
+**_LIBCPP_INNER_CLASS_IN_TEMPLATE_VIS**
+  To keep binary compatibility purpose only of a class not marked as `dllexport`
+  that is defined in a class template. Not to add this for new class, and this
+  can be replaced to `_LIBCPP_EXPORTED_FROM_ABI` at a timing of ABI change occurs.
+
 Links
 =====
 

libcxx/include/__config

@@ -365,6 +365,11 @@ typedef __char32_t char32_t;
 #      define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
 #      define _LIBCPP_OVERRIDABLE_FUNC_VIS
 #      define _LIBCPP_EXPORTED_FROM_ABI
+#      if defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS) || !__has_attribute(exclude_from_explicit_instantiation)
+#        define _LIBCPP_INNER_CLASS_IN_TEMPLATE_VIS
+#      else
+#        define _LIBCPP_INNER_CLASS_IN_TEMPLATE_VIS __attribute__((__exclude_from_explicit_instantiation__))
+#      endif
 #    elif defined(_LIBCPP_BUILDING_LIBRARY)
 #      if defined(__MINGW32__)
 #        define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __declspec(dllexport)
@@ -375,11 +380,13 @@ typedef __char32_t char32_t;
 #      endif
 #      define _LIBCPP_OVERRIDABLE_FUNC_VIS __declspec(dllexport)
 #      define _LIBCPP_EXPORTED_FROM_ABI __declspec(dllexport)
+#      define _LIBCPP_INNER_CLASS_IN_TEMPLATE_VIS
 #    else
 #      define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __declspec(dllimport)
 #      define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
 #      define _LIBCPP_OVERRIDABLE_FUNC_VIS
 #      define _LIBCPP_EXPORTED_FROM_ABI __declspec(dllimport)
+#      define _LIBCPP_INNER_CLASS_IN_TEMPLATE_VIS
 #    endif
 
 #    define _LIBCPP_HIDDEN
@@ -399,6 +406,7 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_EXPORTED_FROM_ABI _LIBCPP_VISIBILITY("default")
 #    define _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS _LIBCPP_VISIBILITY("default")
 #    define _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS
+#    define _LIBCPP_INNER_CLASS_IN_TEMPLATE_VIS
 
 // TODO: Make this a proper customization point or remove the option to override it.
 #    ifndef _LIBCPP_OVERRIDABLE_FUNC_VIS

libcxx/include/__ostream/basic_ostream.h

@@ -71,7 +71,7 @@ class basic_ostream : virtual public basic_ios<_CharT, _Traits> {
 
 public:
   // 27.7.2.4 Prefix/suffix:
-  class sentry;
+  class _LIBCPP_INNER_CLASS_IN_TEMPLATE_VIS sentry;
 
   // 27.7.2.6 Formatted output:
   inline _LIBCPP_HIDE_FROM_ABI_AFTER_V1 basic_ostream& operator<<(basic_ostream& (*__pf)(basic_ostream&)) {

libcxx/include/istream

@@ -228,7 +228,7 @@ public:
   basic_istream& operator=(const basic_istream& __rhs) = delete;
 
   // 27.7.1.1.3 Prefix/suffix:
-  class sentry;
+  class _LIBCPP_INNER_CLASS_IN_TEMPLATE_VIS sentry;
 
   // 27.7.1.2 Formatted input:
   inline _LIBCPP_HIDE_FROM_ABI_AFTER_V1 basic_istream& operator>>(basic_istream& (*__pf)(basic_istream&)) {