[libcxx-commits] [PATCH] D134473: [libc++] Keep unary_function and binary_function in C++17 for one more release

[Louis Dionne via Phabricator via libcxx-commits]

ldionne created this revision.
ldionne added reviewers: thieta, philnik.
Herald added a project: All.
ldionne requested review of this revision.
Herald added a project: libc++.
Herald added a subscriber: libcxx-commits.
Herald added a reviewer: libc++.

In LLVM 15, we added the deprecation markup for unary_function and
binary_function for >= C++11, and we also removed it for >= C++17.
While this is in accordance with the Standard, it's also a bit quick
for our users, since there was no release in which the classes were
marked as deprecated before their removal.

We noticed widespread breakage due to this, and after months of trying
to fix downstream failures, I am coming to the conclusion that users
will be better served if we give them one release where unary_function
is deprecated but still provided even in >= C++17.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D134473

Files:
  libcxx/docs/ReleaseNotes.rst
  libcxx/include/__config
  libcxx/include/__functional/binary_function.h
  libcxx/include/__functional/unary_function.h


Index: libcxx/include/__functional/unary_function.h
===================================================================
--- libcxx/include/__functional/unary_function.h
+++ libcxx/include/__functional/unary_function.h
@@ -22,8 +22,8 @@
 template <class _Arg, class _Result>
 struct _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 unary_function
 {
-    typedef _Arg    argument_type;
-    typedef _Result result_type;
+    typedef _Arg    argument_type _LIBCPP_DEPRECATED_IN_CXX17;
+    typedef _Result result_type _LIBCPP_DEPRECATED_IN_CXX17;
 };
 
 #endif // _LIBCPP_STD_VER <= 14
Index: libcxx/include/__functional/binary_function.h
===================================================================
--- libcxx/include/__functional/binary_function.h
+++ libcxx/include/__functional/binary_function.h
@@ -23,9 +23,9 @@
 template <class _Arg1, class _Arg2, class _Result>
 struct _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 binary_function
 {
-    typedef _Arg1   first_argument_type;
-    typedef _Arg2   second_argument_type;
-    typedef _Result result_type;
+    typedef _Arg1   first_argument_type _LIBCPP_DEPRECATED_IN_CXX17;
+    typedef _Arg2   second_argument_type _LIBCPP_DEPRECATED_IN_CXX17;
+    typedef _Result result_type _LIBCPP_DEPRECATED_IN_CXX17;
 };
 
 #endif // _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_UNARY_BINARY_FUNCTION)
Index: libcxx/include/__config
===================================================================
--- libcxx/include/__config
+++ libcxx/include/__config
@@ -1101,6 +1101,13 @@
 #    define _LIBCPP_ENABLE_CXX17_REMOVED_UNARY_BINARY_FUNCTION
 #  endif // _LIBCPP_ENABLE_CXX17_REMOVED_FEATURES
 
+// Leave the deprecation notices in by default, but don't remove unary_function and
+// binary_function entirely just yet. That way, folks will have one release to act
+// on the deprecation warnings.
+#  ifndef _LIBCPP_ENABLE_CXX17_REMOVED_UNARY_BINARY_FUNCTION
+#    define _LIBCPP_ENABLE_CXX17_REMOVED_UNARY_BINARY_FUNCTION
+#  endif
+
 #  if defined(_LIBCPP_ENABLE_CXX20_REMOVED_FEATURES)
 #    define _LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_MEMBERS
 #    define _LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_VOID_SPECIALIZATION
Index: libcxx/docs/ReleaseNotes.rst
===================================================================
--- libcxx/docs/ReleaseNotes.rst
+++ libcxx/docs/ReleaseNotes.rst
@@ -141,11 +141,10 @@
   or upgrade to C++11 or later. It is possible to re-enable ``std::function`` in C++03 by defining
   ``_LIBCPP_ENABLE_CXX03_FUNCTION``. This option will be removed in LLVM 16.
 
-- ``unary_function`` and ``binary_function`` are no longer available in C++17 and C++20.
-  They can be re-enabled by defining ``_LIBCPP_ENABLE_CXX17_REMOVED_UNARY_BINARY_FUNCTION``.
-  They are also marked as ``[[deprecated]]`` in C++11 and later. To disable deprecation warnings
-  you have to define ``_LIBCPP_DISABLE_DEPRECATION_WARNINGS``. Note that this disables
-  all deprecation warnings.
+- ``unary_function`` and ``binary_function`` are marked as ``[[deprecated]]`` in C++11 and later.
+  To disable deprecation warnings you have to define ``_LIBCPP_DISABLE_DEPRECATION_WARNINGS``. Note
+  that this disables all deprecation warnings. Also note that per the Standard, ``unary_function``
+  and ``binary_function`` will be removed in C++17 and above starting in the next release.
 
 - The contents of ``<codecvt>``, ``wstring_convert`` and ``wbuffer_convert`` have been marked as deprecated.
   To disable deprecation warnings you have to define ``_LIBCPP_DISABLE_DEPRECATION_WARNINGS``. Note that this


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D134473.462278.patch
Type: text/x-patch
Size: 3582 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/libcxx-commits/attachments/20220922/7a52778f/attachment.bin>