[libcxx-commits] [libcxx] [libc++] Remove allocator support from std::function (PR #140395)

[Nikolas Klauser via libcxx-commits]

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@@ -257,84 +176,38 @@ class __base<_Rp(_ArgTypes...)> {
 
 // __func implements __base for a given functor type.
 
-template <class _FD, class _Alloc, class _FB>
+template <class _FD, class _FB>
 class __func;
 
-template <class _Fp, class _Alloc, class _Rp, class... _ArgTypes>
-class __func<_Fp, _Alloc, _Rp(_ArgTypes...)> : public __base<_Rp(_ArgTypes...)> {
-  __alloc_func<_Fp, _Alloc, _Rp(_ArgTypes...)> __f_;
+template <class _Fp, class _Rp, class... _ArgTypes>
+class __func<_Fp, _Rp(_ArgTypes...)> : public __base<_Rp(_ArgTypes...)> {
+  _Fp __func_;
 
 public:
-  _LIBCPP_HIDE_FROM_ABI explicit __func(_Fp&& __f) : __f_(std::move(__f)) {}
-
-  _LIBCPP_HIDE_FROM_ABI explicit __func(const _Fp& __f, const _Alloc& __a) : __f_(__f, __a) {}
+  _LIBCPP_HIDE_FROM_ABI explicit __func(_Fp&& __f) : __func_(std::move(__f)) {}
+  _LIBCPP_HIDE_FROM_ABI explicit __func(const _Fp& __f) : __func_(__f) {}
 
-  _LIBCPP_HIDE_FROM_ABI explicit __func(const _Fp& __f, _Alloc&& __a) : __f_(__f, std::move(__a)) {}
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL __base<_Rp(_ArgTypes...)>* __clone() const override { return new __func(__func_); }
 
-  _LIBCPP_HIDE_FROM_ABI explicit __func(_Fp&& __f, _Alloc&& __a) : __f_(std::move(__f), std::move(__a)) {}
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL void __clone(__base<_Rp(_ArgTypes...)>* __p) const override {
+    ::new ((void*)__p) __func(__func_);
+  }
 
-  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual __base<_Rp(_ArgTypes...)>* __clone() const;
-  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __clone(__base<_Rp(_ArgTypes...)>*) const;
-  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void destroy() _NOEXCEPT;
-  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void destroy_deallocate() _NOEXCEPT;
-  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual _Rp operator()(_ArgTypes&&... __arg);
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL void destroy() _NOEXCEPT override { __func_.~_Fp(); }
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL void destroy_deallocate() _NOEXCEPT override { delete this; }
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL _Rp operator()(_ArgTypes&&... __arg) override {
+    return std::__invoke_r<_Rp>(__func_, std::forward<_ArgTypes>(__arg)...);
+  }
 #  if _LIBCPP_HAS_RTTI
-  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual const void* target(const type_info&) const _NOEXCEPT;
-  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual const std::type_info& target_type() const _NOEXCEPT;
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL const void* target(const type_info& __ti) const _NOEXCEPT override {
+    if (__ti == typeid(_Fp))
+      return std::addressof(__func_);
+    return nullptr;
+  }
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL const std::type_info& target_type() const _NOEXCEPT override { return typeid(_Fp); }
 #  endif // _LIBCPP_HAS_RTTI
 };
 
-template <class _Fp, class _Alloc, class _Rp, class... _ArgTypes>
-__base<_Rp(_ArgTypes...)>* __func<_Fp, _Alloc, _Rp(_ArgTypes...)>::__clone() const {
-  typedef allocator_traits<_Alloc> __alloc_traits;
-  typedef __rebind_alloc<__alloc_traits, __func> _Ap;
-  _Ap __a(__f_.__get_allocator());
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philnik777 wrote:

The allocator was taken into account in a bunch of places. Since C++17 it was simply impossible for `_Alloc` to be anything but `std::allocator`, and even before it was really hard to make it anything different.

https://github.com/llvm/llvm-project/pull/140395