[libc++] Add missing hide-from-ABI annotations on virtual functions (#85439)

Author: ldionne

libcxx/include/__functional/function.h

@@ -768,7 +768,7 @@ class __func<_Rp1 (^)(_ArgTypes1...), _Alloc, _Rp(_ArgTypes...)> : public __base
   {
   }
 
-  virtual __base<_Rp(_ArgTypes...)>* __clone() const {
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual __base<_Rp(_ArgTypes...)>* __clone() const {
     _LIBCPP_ASSERT_INTERNAL(
         false,
         "Block pointers are just pointers, so they should always fit into "
@@ -777,34 +777,40 @@ class __func<_Rp1 (^)(_ArgTypes1...), _Alloc, _Rp(_ArgTypes...)> : public __base
     return nullptr;
   }
 
-  virtual void __clone(__base<_Rp(_ArgTypes...)>* __p) const { ::new ((void*)__p) __func(__f_); }
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void __clone(__base<_Rp(_ArgTypes...)>* __p) const {
+    ::new ((void*)__p) __func(__f_);
+  }
 
-  virtual void destroy() _NOEXCEPT {
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void destroy() _NOEXCEPT {
 #    ifndef _LIBCPP_HAS_OBJC_ARC
     if (__f_)
       _Block_release(__f_);
 #    endif
     __f_ = 0;
   }
 
-  virtual void destroy_deallocate() _NOEXCEPT {
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual void destroy_deallocate() _NOEXCEPT {
     _LIBCPP_ASSERT_INTERNAL(
         false,
         "Block pointers are just pointers, so they should always fit into "
         "std::function's small buffer optimization. This function should "
         "never be invoked.");
   }
 
-  virtual _Rp operator()(_ArgTypes&&... __arg) { return std::__invoke(__f_, std::forward<_ArgTypes>(__arg)...); }
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual _Rp operator()(_ArgTypes&&... __arg) {
+    return std::__invoke(__f_, std::forward<_ArgTypes>(__arg)...);
+  }
 
 #    ifndef _LIBCPP_HAS_NO_RTTI
-  virtual const void* target(type_info const& __ti) const _NOEXCEPT {
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual const void* target(type_info const& __ti) const _NOEXCEPT {
     if (__ti == typeid(__func::__block_type))
       return &__f_;
     return (const void*)nullptr;
   }
 
-  virtual const std::type_info& target_type() const _NOEXCEPT { return typeid(__func::__block_type); }
+  _LIBCPP_HIDE_FROM_ABI_VIRTUAL virtual const std::type_info& target_type() const _NOEXCEPT {
+    return typeid(__func::__block_type);
+  }
 #    endif // _LIBCPP_HAS_NO_RTTI
 };