Avoid warning with rvalue construction without local storage

Author: nvmkuruc

pxr/base/tf/smallVector.h

@@ -156,7 +156,6 @@ template <typename T, uint32_t N>
 class TfSmallVector : public TfSmallVectorBase
 {
 public:
-
     /// XXX: Functionality currently missing, and which we would like to add as
     ///  needed:
     ///     - emplace
@@ -240,8 +239,12 @@ class TfSmallVector : public TfSmallVectorBase
         // sizes. Note that capacities will be the same in this case, so no
         // need to swap those.
         else {
-            _UninitializedMove(rhs.begin(), rhs.end(), begin());
-            rhs._Destruct();
+            // If N is 0, this means that rhs is empty and there are no elements that need moving or destroying
+            // This avoids warnings in GCC.
+            if constexpr (N > 0) {
+                _UninitializedMove(rhs.begin(), rhs.end(), begin());
+                rhs._Destruct();
+            }
         }
         std::swap(_size, rhs._size);
     }

pxr/base/tf/testenv/smallVector.cpp

@@ -319,6 +319,33 @@ testNoLocalStorage()
     TF_AXIOM(v.capacity() == 4);
 }
 
+static void
+testEmptyMoveNoLocalStorage()
+{
+    TfSmallVector<int, 0> empty{};
+    {
+        // Empty move construction
+        TfSmallVector<int, 0> v{std::move(empty)};
+        TF_AXIOM(v.size() == 0);
+        TF_AXIOM(v.capacity() == 0);
+
+        v.push_back(1414);
+        TF_AXIOM(v.size() == 1);
+        TF_AXIOM(v.capacity() == 1);
+        TF_AXIOM(v.front() == 1414);
+        TF_AXIOM(v.back() == 1414);
+
+        v.push_back(1515);
+        TF_AXIOM(v.size() == 2);
+        TF_AXIOM(v.capacity() == 2);
+        TF_AXIOM(v.front() == 1414);
+        TF_AXIOM(v.back() == 1515);
+    }
+
+    TF_AXIOM(empty.size() == 0);
+    TF_AXIOM(empty.capacity() == 0);
+}
+
 static void
 testGrowth()
 {
@@ -1588,6 +1615,8 @@ Test_TfSmallVector()
     testConstructors();
     std::cout << "testNoLocalStorage" << std::endl;
     testNoLocalStorage();
+    std::cout << "testEmptyMoveNoLocalStorage" << std::endl;
+    testEmptyMoveNoLocalStorage();
     std::cout << "testGrowth" << std::endl;
     testGrowth();
     std::cout << "testIteration" << std::endl;