small_vector<T>::get_allocator()

Summary:
[Folly] `small_vector<T>::get_allocator()` for compatibility with other container types.

While `small_vector` is not actually parameterizable over the allocator types, compatibility with generic interfaces such as the presorted-ctor interfaces of `sorted_vector_set` and `sorted_vector_map` require `get_allocator`.

Reviewed By: vitaut

Differential Revision: D15194509

fbshipit-source-id: 3a7842d5640f8e95a09c4cd8e2a9ab6ffc4fe9ac

folly/small_vector.h

@@ -459,6 +459,7 @@ class small_vector : public detail::small_vector_base<
  public:
   typedef std::size_t size_type;
   typedef Value value_type;
+  typedef std::allocator<Value> allocator_type;
   typedef value_type& reference;
   typedef value_type const& const_reference;
   typedef value_type* iterator;
@@ -562,6 +563,10 @@ class small_vector : public detail::small_vector_base<
                                      : BaseType::policyMaxSize();
   }
 
+  allocator_type get_allocator() {
+    return {};
+  }
+
   size_type size() const {
     return this->doSize();
   }