[ADT] Explicitly delete copy/move constructors and operator= in IntervalMap

The default implementations will perform a shallow copy instead of a deep
copy, causing some internal data structures to be shared between different
objects. Disable these operations so they don't get accidentally used.

Differential Revision: https://reviews.llvm.org/D126401

Author: Krzysztof Parzyszek

llvm/include/llvm/ADT/IntervalMap.h

@@ -1042,6 +1042,17 @@ class IntervalMap {
     new(&rootLeaf()) RootLeaf();
   }
 
+  // The default copy/move constructors and assignment operators would perform
+  // a shallow copy, leading to an incorrect internal state. To prevent
+  // accidental use, explicitly delete these operators.
+  // If necessary, implement them to perform a deep copy.
+  IntervalMap(const IntervalMap &Other) = delete;
+  IntervalMap(IntervalMap &&Other) = delete;
+  // Note: these are already implicitly deleted, because RootLeaf (union
+  // member) has a non-trivial assignment operator (because of std::pair).
+  IntervalMap &operator=(const IntervalMap &Other) = delete;
+  IntervalMap &operator=(IntervalMap &&Other) = delete;
+
   ~IntervalMap() {
     clear();
     rootLeaf().~RootLeaf();

llvm/unittests/ADT/IntervalMapTest.cpp

@@ -8,6 +8,7 @@
 
 #include "llvm/ADT/IntervalMap.h"
 #include "gtest/gtest.h"
+#include <type_traits>
 
 using namespace llvm;
 
@@ -17,6 +18,15 @@ typedef IntervalMap<unsigned, unsigned, 4> UUMap;
 typedef IntervalMap<unsigned, unsigned, 4,
                     IntervalMapHalfOpenInfo<unsigned>> UUHalfOpenMap;
 
+static_assert(!std::is_copy_constructible<UUMap>::value,
+              "IntervalMap copy constructor should be deleted");
+static_assert(!std::is_move_constructible<UUMap>::value,
+              "IntervalMap move constructor should be deleted");
+static_assert(!std::is_copy_assignable<UUMap>::value,
+              "IntervalMap copy assignment should be deleted");
+static_assert(!std::is_move_assignable<UUMap>::value,
+              "IntervalMap move assignment should be deleted");
+
 // Empty map tests
 TEST(IntervalMapTest, EmptyMap) {
   UUMap::Allocator allocator;