cross_system_copy_n: Dont attempt a copy if we're tyring to copy 0 el…

…ements Attempting to perform this copy with 0 elements caused a debug assertion when compiling with MSVC in debug mode. Fixes #1275
NVIDIA · Nov 5, 2020 · 1c4f25d · 1c4f25d
1 parent 5df7084
commit 1c4f25d
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Showing 2 changed files with 20 additions and 6 deletions.
diff --git a/testing/vector.cu b/testing/vector.cu
@@ -644,6 +644,19 @@ DECLARE_VECTOR_UNITTEST(TestVectorReserving)
 
 
 
+template <class Vector>
+void TestVectorUninitialisedCopy(void)
+{
+    thrust::device_vector<int> v;
+    std::vector<int> std_vector;
+
+    v = std_vector;
+
+    ASSERT_EQUAL(v.size(), static_cast<size_t>(0));
+}
+DECLARE_VECTOR_UNITTEST(TestVectorUninitialisedCopy);
+
+
 template <class Vector>
 void TestVectorShrinkToFit(void)
 {

diff --git a/thrust/system/cuda/detail/internal/copy_cross_system.h b/thrust/system/cuda/detail/internal/copy_cross_system.h
@@ -100,12 +100,13 @@ namespace __copy {
 
   {
     typedef typename iterator_traits<InputIt>::value_type InputTy;
-
-    trivial_device_copy(derived_cast(sys1),
-                        derived_cast(sys2),
-                        reinterpret_cast<InputTy*>(thrust::raw_pointer_cast(&*result)),
-                        reinterpret_cast<InputTy const*>(thrust::raw_pointer_cast(&*begin)),
-                        n);
+    if (n > 0) {
+      trivial_device_copy(derived_cast(sys1),
+                          derived_cast(sys2),
+                          reinterpret_cast<InputTy*>(thrust::raw_pointer_cast(&*result)),
+                          reinterpret_cast<InputTy const*>(thrust::raw_pointer_cast(&*begin)),
+                          n);
+    }
 
     return result + n;
   }