[libc++] Remove <functional> includes

[Mordante]

Thanks for the cleanup.

libcxx/docs/ReleaseNotes.rst

74

I feel this list is getting at the point were it becomes hard to read, and I expect the list to keep growing. I would suggest to change this entry to

- Some libc++ headers no longer transitively include all of
  
  - ``<algorithm>``,
  - ``<chrono>``,
  - ``<functional>``, and
  - ``<utility>``.

  If, after updating libc++, you see compiler errors related to missing declarations in namespace ``std``,
  it might be because one of your source files now needs to include one or more of the above headers.

(The formatting is untested.)

If you want to keep it as is, then please add Oxford comma's in both listings. (The first also misses a space.)

``<functional>``, and ``<utility>``. If, after updating libc++, you see compiler errors

[philnik]

• Update Release Notes

[var-const]

@philnik Can you add some more context to the patch and commit description? I think it would be useful to explain why it's safe to do this change now, at least.

LGTM, but because it can be a breaking change for users, please wait for @ldionne to review.

libcxx/docs/ReleaseNotes.rst

70–78

Nit: I think it would make sense to add a colon after of to precede the list.

71

Optional: I think it's more common for list elements to end in ; semicolons.

73

I'd remove this and -- it seems largely like a leftover from the previous state when this was a sentence and not a list.

[philnik]

• Address comments

[philnik]

@var-const What would you like to see in the description? The consensus was that we remove a few of the transitive includes in the libc++15 release cycle.
I don't think that Louis has to take a look here, since he approved of the direction. The entire reason this is in it's own patch is to be able to easily revert it just in case we break something in a really bad way.

libcxx/docs/ReleaseNotes.rst

71

I think it makes more sense to remove them entirely.

[ldionne]

LGTM. I understand that this will probably cause a bit of breakage, but it's trivial to fix and we have to get going if we ever want to clean up our transitive includes.

Pinging libc++ vendors for awareness.

libcxx/docs/ReleaseNotes.rst

- The ``_LIBCPP_ABI_UNSTABLE`` macro has been removed in favour of setting
   they were not supposed to set ``_LIBCPP_ABI_UNSTABLE`` manually, however we
   still feel that it is worth mentioning in the release notes in case some users
   had been doing it.
 
 - The header ``<experimental/filesystem>`` has been removed. Instead, use
   ``<filesystem>`` header. The associated macro
   ``_LIBCPP_DEPRECATED_EXPERIMENTAL_FILESYSTEM`` has also been removed.
 
-- Some libc++ headers no longer transitively include all of ``<algorithm>``, ``<chrono>`` and ``<utility>``.
-  If, after updating libc++, you see compiler errors related to missing declarations in
-  namespace ``std``, it might be because one of your source files now needs to
-  ``#include <algorithm>``, ``#include <chrono>`` and/or ``#include <utility>``.
+- Some libc++ headers no longer transitively include all of:
+    - ``<algorithm>``
+    - ``<chrono>``
+    - ``<functional>``
+    - ``<utility>``
+
+  If, after updating libc++, you see compiler errors related to missing declarations
+  in namespace ``std``, it might be because one of your source files now needs to
+  include one or more of the headers listed above.
 
 - The integer distributions ``binomial_distribution``, ``discrete_distribution``,
   ``geometric_distribution``, ``negative_binomial_distribution``, ``poisson_distribution``,
   and ``uniform_int_distribution`` now conform to the Standard by rejecting
   template parameter types other than ``short``, ``int``, ``long``, ``long long``,
   (as an extension) ``__int128_t``, and the unsigned versions thereof.
   In particular, ``uniform_int_distribution<int8_t>`` is no longer supported.
 

libcxx/include/algorithm

 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__bits>
 #include <__config>
 #include <__debug>
 #include <cstddef>
 #include <cstring>
-#include <functional> // TODO: Remove this include
 #include <initializer_list>
 #include <iterator>
 #include <memory>
 #include <type_traits>
 #include <version>
 
 #include <__algorithm/adjacent_find.h>
 #include <__algorithm/all_of.h>

libcxx/include/experimental/coroutine

 } // namespace std
 
  */
 
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__functional/hash.h>
 #include <cstddef>
 #include <experimental/__config>
-#include <functional> // TODO: Remove this include
 #include <memory> // for hash<T*>
 #include <new>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 

libcxx/include/experimental/propagate_const

 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__functional/operations.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <__utility/swap.h>
 #include <experimental/__config>
-#include <functional> // TODO: Remove this include
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 #if _LIBCPP_STD_VER > 11
 

libcxx/include/experimental/simd

 
 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__functional/operations.h>
 #include <array>
 #include <cstddef>
 #include <experimental/__config>
-#include <functional> // TODO: Remove this include
 #include <tuple>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_PUSH_MACROS
 #include <__undef_macros>

libcxx/include/ext/hash_map

 
 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 #include <__hash_table>
 #include <algorithm>
 #include <ext/__hash>
-#include <functional> // TODO: Remove this include
 #include <stdexcept>
 #include <type_traits>
 
 #if defined(__DEPRECATED) && __DEPRECATED
 #if defined(_LIBCPP_WARNING)
     _LIBCPP_WARNING("Use of the header <ext/hash_map> is deprecated.  Migrate to <unordered_map>")
 #else
 #   warning Use of the header <ext/hash_map> is deprecated.  Migrate to <unordered_map>

libcxx/include/ext/hash_set

 
 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 #include <__hash_table>
 #include <algorithm>
 #include <ext/__hash>
-#include <functional> // TODO: Remove this include
 
 #if defined(__DEPRECATED) && __DEPRECATED
 #if defined(_LIBCPP_WARNING)
     _LIBCPP_WARNING("Use of the header <ext/hash_set> is deprecated.  Migrate to <unordered_set>")
 #else
 #   warning Use of the header <ext/hash_set> is deprecated.  Migrate to <unordered_set>
 #endif
 #endif

libcxx/include/map

 #include <__config>
 #include <__functional/is_transparent.h>
 #include <__iterator/iterator_traits.h>
 #include <__node_handle>
 #include <__tree>
 #include <__utility/forward.h>
 #include <__utility/swap.h>
 #include <compare>
-#include <functional> // TODO: Remove this include
 #include <initializer_list>
 #include <iterator> // __libcpp_erase_if_container
 #include <memory>
 #include <type_traits>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header

libcxx/include/mutex

 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 #include <__mutex_base>
 #include <__threading_support>
 #include <__utility/forward.h>
 #include <cstdint>
-#include <functional> // TODO: Remove this include
 #include <memory>
 #ifndef _LIBCPP_CXX03_LANG
 # include <tuple>
 #endif
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header

libcxx/include/numeric

 
 }  // std
 
 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 #include <cmath> // for isnormal
-#include <functional> // TODO: Remove this include
 #include <iterator>
 #include <version>
 
 #include <__numeric/accumulate.h>
 #include <__numeric/adjacent_difference.h>
 #include <__numeric/exclusive_scan.h>
 #include <__numeric/gcd_lcm.h>
 #include <__numeric/inclusive_scan.h>

libcxx/include/optional

 #include <__functional/unary_function.h>
 #include <__memory/construct_at.h>
 #include <__tuple>
 #include <__utility/forward.h>
 #include <__utility/in_place.h>
 #include <__utility/move.h>
 #include <__utility/swap.h>
 #include <compare>
-#include <functional> // TODO: Remove this include
 #include <initializer_list>
 #include <new>
 #include <stdexcept>
 #include <type_traits>
 #include <version>
 
 // TODO: remove these headers
 #include <__memory/allocator_arg_t.h>

libcxx/include/queue

 #include <__algorithm/push_heap.h>
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 #include <__iterator/iterator_traits.h>
 #include <__memory/uses_allocator.h>
 #include <__utility/forward.h>
 #include <compare>
 #include <deque>
-#include <functional> // TODO: Remove this include
 #include <type_traits>
 #include <vector>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 

libcxx/include/set

 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 #include <__functional/is_transparent.h>
 #include <__iterator/iterator_traits.h>
 #include <__node_handle>
 #include <__tree>
 #include <__utility/forward.h>
 #include <compare>
-#include <functional> // TODO: Remove this include
 #include <initializer_list>
 #include <iterator> // __libcpp_erase_if_container
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 

libcxx/include/thread

 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 #include <__mutex_base>
 #include <__thread/poll_with_backoff.h>
 #include <__thread/timed_backoff_policy.h>
 #include <__threading_support>
 #include <__utility/forward.h>
 #include <cstddef>
-#include <functional> // TODO: Remove this include
 #include <iosfwd>
 #include <memory>
 #include <system_error>
 #include <tuple>
 #include <type_traits>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)

libcxx/include/unordered_map

 #include <__debug>
 #include <__functional/is_transparent.h>
 #include <__hash_table>
 #include <__iterator/iterator_traits.h>
 #include <__memory/addressof.h>
 #include <__node_handle>
 #include <__utility/forward.h>
 #include <compare>
-#include <functional> // TODO: Remove this include
 #include <iterator> // __libcpp_erase_if_container
 #include <stdexcept>
 #include <tuple>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif

libcxx/include/unordered_set

 #include <__config>
 #include <__debug>
 #include <__functional/is_transparent.h>
 #include <__hash_table>
 #include <__memory/addressof.h>
 #include <__node_handle>
 #include <__utility/forward.h>
 #include <compare>
-#include <functional> // TODO: Remove this include
 #include <iterator> // __libcpp_erase_if_container
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD

libcxx/include/valarray

 #include <__config>
 #include <__functional/operations.h>
 #include <__memory/allocator.h>
 #include <__memory/uninitialized_algorithms.h>
 #include <__utility/move.h>
 #include <__utility/swap.h>
 #include <cmath>
 #include <cstddef>
-#include <functional> // TODO: Remove this include
 #include <initializer_list>
 #include <new>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif