[libc++] Make everything in namespace std have default type visibility and hidden visibility and remove _LIBCPP_ENUM_VIS

This avoids having to add `_LIBCPP_ENUM_VIS`, since that is handled through `type_visibility` and GCC always makes the visibility of enums default. It also fixes and missing `_LIBCPP_EXPORTED_FROM_ABI` on classes when using Clang.

Reviewed By: ldionne, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D153658

Author: philnik777

libcxx/.clang-format

@@ -30,7 +30,6 @@ AttributeMacros: [
                   '_LIBCPP_DEPRECATED_IN_CXX20',
                   '_LIBCPP_DEPRECATED',
                   '_LIBCPP_DISABLE_EXTENTSION_WARNING',
-                  '_LIBCPP_ENUM_VIS',
                   '_LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION',
                   '_LIBCPP_EXPORTED_FROM_ABI',
                   '_LIBCPP_EXTERN_TEMPLATE_TYPE_VIS',

libcxx/docs/DesignDocs/VisibilityMacros.rst

@@ -14,6 +14,13 @@ Libc++ uses various "visibility" macros in order to provide a stable ABI in
 both the library and the headers. These macros work by changing the
 visibility and inlining characteristics of the symbols they are applied to.
 
+The std namespace also has visibility attributes applied to avoid having to
+add visibility macros in as many places. Namespace std has default
+type_visibility to export RTTI and other type-specific information. Note that
+type_visibility is only supported by Clang, so this doesn't replace
+type-specific attributes. The only exception are enums, which GCC always gives
+default visibility, thus removing the need for any annotations.
+
 Visibility Macros
 =================
 
@@ -72,19 +79,6 @@ Visibility Macros
   **Windows Behavior**: DLLs do not support dllimport/export on class templates.
   The macro has an empty definition on this platform.
 
-
-**_LIBCPP_ENUM_VIS**
-  Mark the typeinfo of an enum as having default visibility. This attribute
-  should be applied to all enum declarations.
-
-  **Windows Behavior**: DLLs do not support importing or exporting enumeration
-  typeinfo. The macro has an empty definition on this platform.
-
-  **GCC Behavior**: GCC un-hides the typeinfo for enumerations by default, even
-  if `-fvisibility=hidden` is specified. Additionally applying a visibility
-  attribute to an enum class results in a warning. The macro has an empty
-  definition with GCC.
-
 **_LIBCPP_EXTERN_TEMPLATE_TYPE_VIS**
   Mark the member functions, typeinfo, and vtable of the type named in
   an extern template declaration as being exported by the libc++ library.

libcxx/docs/ReleaseNotes/18.rst

@@ -77,5 +77,13 @@ ABI Affecting Changes
 - The symbol of a non-visible function part of ``std::system_error`` was removed.
   This is not a breaking change as the private function ``__init`` was never referenced internally outside of the dylib
 
+- This release of libc++ added missing visibility annotations on some types in the library. Users compiling with
+  ``-fvisbility=hidden`` may notice that additional type infos from libc++ are being exported from their ABI. This is
+  the correct behavior in almost all cases since exporting the RTTI is required for these types to work properly with
+  dynamic_cast, exceptions and other mechanisms across binaries. However, if you intend to use libc++ purely as an
+  internal implementation detail (i.e. you use libc++ as a static archive and never export libc++ symbols from your ABI)
+  and you notice changes to your exported symbols list, then this means that you were not properly preventing libc++
+  symbols from being part of your ABI.
+
 Build System Changes
 --------------------

libcxx/include/__charconv/chars_format.h

@@ -21,7 +21,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER >= 17
 
-enum class _LIBCPP_ENUM_VIS chars_format { scientific = 0x1, fixed = 0x2, hex = 0x4, general = fixed | scientific };
+enum class chars_format { scientific = 0x1, fixed = 0x2, hex = 0x4, general = fixed | scientific };
 
 inline _LIBCPP_HIDE_FROM_ABI constexpr chars_format operator~(chars_format __x) {
   return chars_format(~std::__to_underlying(__x));

libcxx/include/__compare/ordering.h

@@ -22,13 +22,13 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 #if _LIBCPP_STD_VER >= 20
 
 // exposition only
-enum class _LIBCPP_ENUM_VIS _OrdResult : signed char {
+enum class _OrdResult : signed char {
   __less = -1,
   __equiv = 0,
   __greater = 1
 };
 
-enum class _LIBCPP_ENUM_VIS _NCmpResult : signed char {
+enum class _NCmpResult : signed char {
   __unordered = -127
 };
 

libcxx/include/__config

@@ -685,7 +685,7 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
 #    define _LIBCPP_TEMPLATE_VIS
 #    define _LIBCPP_TEMPLATE_DATA_VIS
-#    define _LIBCPP_ENUM_VIS
+#    define _LIBCPP_TYPE_VISIBILITY_DEFAULT
 
 #  else
 
@@ -713,20 +713,17 @@ typedef __char32_t char32_t;
 #      define _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
 #    endif
 
-#    if !defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS)
-#      if __has_attribute(__type_visibility__)
-#        define _LIBCPP_TEMPLATE_VIS __attribute__((__type_visibility__("default")))
-#      else
-#        define _LIBCPP_TEMPLATE_VIS __attribute__((__visibility__("default")))
-#      endif
+// GCC doesn't support the type_visibility attribute, so we have to keep the visibility attribute on templates
+#    if !defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS) && !__has_attribute(__type_visibility__)
+#      define _LIBCPP_TEMPLATE_VIS __attribute__((__visibility__("default")))
 #    else
 #      define _LIBCPP_TEMPLATE_VIS
 #    endif
 
 #    if !defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS) && __has_attribute(__type_visibility__)
-#      define _LIBCPP_ENUM_VIS __attribute__((__type_visibility__("default")))
+#      define _LIBCPP_TYPE_VISIBILITY_DEFAULT __attribute__((__type_visibility__("default")))
 #    else
-#      define _LIBCPP_ENUM_VIS
+#      define _LIBCPP_TYPE_VISIBILITY_DEFAULT
 #    endif
 
 #  endif // defined(_LIBCPP_OBJECT_FORMAT_COFF)
@@ -800,7 +797,8 @@ typedef __char32_t char32_t;
 
 // Inline namespaces are available in Clang/GCC/MSVC regardless of C++ dialect.
 // clang-format off
-#  define _LIBCPP_BEGIN_NAMESPACE_STD namespace std { inline namespace _LIBCPP_ABI_NAMESPACE {
+#  define _LIBCPP_BEGIN_NAMESPACE_STD namespace _LIBCPP_TYPE_VISIBILITY_DEFAULT std {                                  \
+                               inline namespace _LIBCPP_ABI_NAMESPACE {
 #  define _LIBCPP_END_NAMESPACE_STD }}
 #  define _VSTD std
 
@@ -853,7 +851,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD _LIBCPP_END_NAMESPACE_STD
 // clang-format on
 
 #  else // _LIBCPP_CXX03_LANG
-#    define _LIBCPP_DECLARE_STRONG_ENUM(x) enum class _LIBCPP_ENUM_VIS x
+#    define _LIBCPP_DECLARE_STRONG_ENUM(x) enum class x
 #    define _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(x)
 #  endif // _LIBCPP_CXX03_LANG
 

libcxx/include/__filesystem/copy_options.h

@@ -21,7 +21,7 @@
 
 _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
 
-enum class _LIBCPP_ENUM_VIS copy_options : unsigned short {
+enum class copy_options : unsigned short {
   none = 0,
   skip_existing = 1,
   overwrite_existing = 2,

libcxx/include/__filesystem/directory_options.h

@@ -21,7 +21,7 @@
 
 _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
 
-enum class _LIBCPP_ENUM_VIS directory_options : unsigned char {
+enum class directory_options : unsigned char {
   none = 0,
   follow_directory_symlink = 1,
   skip_permission_denied = 2

libcxx/include/__filesystem/file_type.h

@@ -23,7 +23,7 @@ _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
 
 // On Windows, the library never identifies files as block, character, fifo
 // or socket.
-enum class _LIBCPP_ENUM_VIS file_type : signed char {
+enum class file_type : signed char {
   none = 0,
   not_found = -1,
   regular = 1,

libcxx/include/__filesystem/path.h

@@ -465,7 +465,7 @@ class _LIBCPP_EXPORTED_FROM_ABI path {
   typedef basic_string<value_type> string_type;
   typedef basic_string_view<value_type> __string_view;
 
-  enum _LIBCPP_ENUM_VIS format : unsigned char {
+  enum format : unsigned char {
     auto_format,
     native_format,
     generic_format

libcxx/include/__filesystem/perm_options.h

@@ -21,7 +21,7 @@
 
 _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
 
-enum class _LIBCPP_ENUM_VIS perm_options : unsigned char {
+enum class perm_options : unsigned char {
   replace = 1,
   add = 2,
   remove = 4,

libcxx/include/__filesystem/perms.h

@@ -25,7 +25,7 @@ _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
 // file, and the executable bit is always returned as set. When setting
 // permissions, as long as the write bit is set for either owner, group or
 // others, the readonly flag is cleared.
-enum class _LIBCPP_ENUM_VIS perms : unsigned {
+enum class perms : unsigned {
   none = 0,
 
   owner_read = 0400,

libcxx/include/__format/format_arg.h

@@ -53,7 +53,7 @@ namespace __format {
 /// handle to satisfy the user observable behaviour. The internal function
 /// __visit_format_arg doesn't do this wrapping. So in the format functions
 /// this function is used to avoid unneeded overhead.
-enum class _LIBCPP_ENUM_VIS __arg_t : uint8_t {
+enum class __arg_t : uint8_t {
   __none,
   __boolean,
   __char_type,

libcxx/include/__format/parser_std_format_spec.h

@@ -176,7 +176,7 @@ inline constexpr __fields __fields_range{.__use_range_fill_ = true, .__clear_bra
 inline constexpr __fields __fields_fill_align_width{};
 #  endif
 
-enum class _LIBCPP_ENUM_VIS __alignment : uint8_t {
+enum class __alignment : uint8_t {
   /// No alignment is set in the format string.
   __default,
   __left,
@@ -185,7 +185,7 @@ enum class _LIBCPP_ENUM_VIS __alignment : uint8_t {
   __zero_padding
 };
 
-enum class _LIBCPP_ENUM_VIS __sign : uint8_t {
+enum class __sign : uint8_t {
   /// No sign is set in the format string.
   ///
   /// The sign isn't allowed for certain format-types. By using this value
@@ -197,7 +197,7 @@ enum class _LIBCPP_ENUM_VIS __sign : uint8_t {
   __space
 };
 
-enum class _LIBCPP_ENUM_VIS __type : uint8_t {
+enum class __type : uint8_t {
   __default = 0,
   __string,
   __binary_lower_case,

libcxx/include/__format/write_escaped.h

@@ -118,7 +118,7 @@ template <class _CharT>
   return static_cast<make_unsigned_t<_CharT>>(__value);
 }
 
-enum class _LIBCPP_ENUM_VIS __escape_quotation_mark { __apostrophe, __double_quote };
+enum class __escape_quotation_mark { __apostrophe, __double_quote };
 
 // [format.string.escaped]/2
 template <class _CharT>

libcxx/include/__fwd/subrange.h

@@ -23,7 +23,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 
-enum class _LIBCPP_ENUM_VIS subrange_kind : bool { unsized, sized };
+enum class subrange_kind : bool { unsized, sized };
 
 template <input_or_output_iterator _Iter, sentinel_for<_Iter> _Sent, subrange_kind _Kind>
   requires(_Kind == subrange_kind::sized || !sized_sentinel_for<_Sent, _Iter>)

libcxx/include/new

@@ -185,7 +185,7 @@ void __throw_bad_array_new_length()
 #if !defined(_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION) && \
     !defined(_LIBCPP_ABI_VCRUNTIME)
 #ifndef _LIBCPP_CXX03_LANG
-enum class _LIBCPP_ENUM_VIS align_val_t : size_t { };
+enum class align_val_t : size_t { };
 #else
 enum align_val_t { __zero = 0, __max = (size_t)-1 };
 #endif