Fix memory leak when exception is thrown

Summary: F14NodeSet::insert() leaks memory when construction throws.

Reviewed By: yfeldblum, nbronson

Differential Revision: D16399317

fbshipit-source-id: 4c9385288dd212469dfbd10b3e990b3533dc66d3

folly/container/detail/F14Policy.h

@@ -849,7 +849,9 @@ class NodeContainerPolicy
     auto p = std::addressof(**itemAddr);
     // TODO(T31574848): clean up assume-s used to optimize placement new
     assume(p != nullptr);
+    auto rollback = makeGuard([&] { AllocTraits::deallocate(a, p, 1); });
     AllocTraits::construct(a, p, std::forward<Args>(args)...);
+    rollback.dismiss();
   }
 
   void moveItemDuringRehash(Item* itemAddr, Item& src) {

folly/container/test/F14SetTest.cpp

@@ -1417,6 +1417,21 @@ TEST(F14Set, eraseIf) {
   testEraseIf<F14NodeSet>();
 }
 
+template <template <class...> class TSet>
+void testExceptionOnInsert() {
+  TSet<ThrowOnCopyTestInt> m{};
+  ThrowOnCopyTestInt key;
+  EXPECT_THROW(m.insert(key), std::exception);
+  EXPECT_TRUE(m.empty());
+}
+
+TEST(F14Set, ExceptionOnInsert) {
+  testExceptionOnInsert<F14ValueSet>();
+  testExceptionOnInsert<F14NodeSet>();
+  testExceptionOnInsert<F14VectorSet>();
+  testExceptionOnInsert<F14FastSet>();
+}
+
 ///////////////////////////////////
 #endif // FOLLY_F14_VECTOR_INTRINSICS_AVAILABLE
 ///////////////////////////////////

folly/container/test/F14TestUtil.h

@@ -118,6 +118,30 @@ struct MoveOnlyTestInt {
   }
 };
 
+struct ThrowOnCopyTestInt {
+  int x{0};
+
+  ThrowOnCopyTestInt() {}
+
+  __attribute__((__noreturn__))
+  ThrowOnCopyTestInt(const ThrowOnCopyTestInt& other)
+      : x(other.x) {
+    throw std::exception{};
+  }
+
+  ThrowOnCopyTestInt& operator=(const ThrowOnCopyTestInt&) {
+    throw std::exception{};
+  }
+
+  bool operator==(const ThrowOnCopyTestInt& other) const {
+    return x == other.x;
+  }
+
+  bool operator!=(const ThrowOnCopyTestInt& other) const {
+    return !(x == other.x);
+  }
+};
+
 // Tracked is implicitly constructible across tags
 struct Counts {
   uint64_t copyConstruct{0};
@@ -593,6 +617,13 @@ struct hash<folly::f14::MoveOnlyTestInt> {
   }
 };
 
+template <>
+struct hash<folly::f14::ThrowOnCopyTestInt> {
+  std::size_t operator()(folly::f14::ThrowOnCopyTestInt const& val) const {
+    return val.x;
+  }
+};
+
 template <int Tag>
 struct hash<folly::f14::Tracked<Tag>> {
   size_t operator()(folly::f14::Tracked<Tag> const& tracked) const {