added a unit test

Author: kerambyte

llvm/unittests/ADT/FunctionExtrasTest.cpp

@@ -310,4 +310,23 @@ class Incomplete {};
 Incomplete incompleteFunction() { return {}; }
 const Incomplete incompleteFunctionConst() { return {}; }
 
+// Check that we can store a pointer-sized payload inline in the unique_function.
+TEST(UniqueFunctionTest, InlineStorageWorks) {
+  // We do assume a couple of implementation details of the unique_function here:
+  //  - It can store certain small-enough payload inline
+  //  - Inline storage size is at least >= sizeof(void*)
+  void *ptr;
+  unique_function<void(void *)> UniqueFunctionWithInlineStorage{
+      [ptr](void *self) {
+        auto mid = reinterpret_cast<uintptr_t>(&ptr);
+        auto beg = reinterpret_cast<uintptr_t>(self);
+        auto end = reinterpret_cast<uintptr_t>(self) +
+                   sizeof(unique_function<void(void *)>);
+        // Make sure the address of the captured pointer lies somewhere within
+        // the unique_function object.
+        EXPECT_TRUE(mid >= beg && mid < end);
+      }};
+  UniqueFunctionWithInlineStorage(&UniqueFunctionWithInlineStorage);
+}
+
 } // anonymous namespace