Add InlineStdAllocator::rebind struct member

Newer versions of libc++ (as well as libstdc++) require this of
allocators. This member is needed for
std::allocator_traits<InlineStdAllocator<T, SIZE>>::rebind_alloc<U>,
which contains a typedef for InlineStdAllocator<U>. I believe this
requirement was always present, but libc++ is checking for it now.

AFAICT, the STL wouldn't be able to construct an InlineStdAllocator<U>,
because there is no default constructor, and the copy constructor
wouldn't accept a reference to InlineStdAllocator<T>. Perhaps that's OK
because this allocator is only used with std::vector, not (say)
std::list or std::map, which actually need to allocate internal node
types.

std::allocator_traits::rebind_alloc can automatically handle custom
allocators with type parameters, but not with non-type parameters
(i.e. It can't handle "size_t SIZE = 4"). See
https://stackoverflow.com/a/34863387.

Bug: b/175635923
Test: treehugger
Change-Id: I0cceb47ab780414202cef1ed54fa7deb3773d01a

1 files changed, 11 insertions, 0 deletions

diff --git a/libs/ui/include/ui/FatVector.h b/libs/ui/include/ui/FatVector.h
index cb61e6a320..494272b1a8 100644
--- a/libs/ui/include/ui/FatVector.h
+++ b/libs/ui/include/ui/FatVector.h
@@ -65,6 +65,17 @@ public:
             free(p);
         }
     }
+
+    // The STL checks that this member type is present so that
+    // std::allocator_traits<InlineStdAllocator<T, SIZE>>::rebind_alloc<Other>
+    // works. std::vector won't be able to construct an
+    // InlineStdAllocator<Other, SIZE>, because InlineStdAllocator has no
+    // default constructor, but vector presumably doesn't rebind the allocator
+    // because it doesn't allocate internal node types.
+    template <class Other>
+    struct rebind {
+        typedef InlineStdAllocator<Other, SIZE> other;
+    };
     Allocation& mAllocation;
 };