fix: allow null data for empty binary and string views during append

src/nanoarrow/common/array_test.cc

@@ -1193,6 +1193,30 @@ TEST(ArrayTest, ArrayTestAppendToStringViewArray) {
   });
 };
 
+TEST(ArrayTest, ArrayTestAppendNullDataToViewArray) {
+  for (enum ArrowType arrow_type :
+       {NANOARROW_TYPE_BINARY_VIEW, NANOARROW_TYPE_STRING_VIEW}) {
+    SCOPED_TRACE(ArrowTypeString(arrow_type));
+    nanoarrow::UniqueArray array;
+    ASSERT_EQ(ArrowArrayInitFromType(array.get(), arrow_type), NANOARROW_OK);
+    ASSERT_EQ(ArrowArrayStartAppending(array.get()), NANOARROW_OK);
+
+    // Empty buffer and string views may have a null data pointer.
+    // Run with UBSan to detect passing these pointers to memcpy, even with size 0.
+    ASSERT_EQ(ArrowArrayAppendBytes(array.get(), {{nullptr}, 0}), NANOARROW_OK);
+    ASSERT_EQ(ArrowArrayAppendString(array.get(), ArrowCharView(nullptr)), NANOARROW_OK);
+    ASSERT_EQ(ArrowArrayFinishBuildingDefault(array.get(), nullptr), NANOARROW_OK);
+
+    EXPECT_EQ(array->length, 2);
+    EXPECT_EQ(array->null_count, 0);
+    auto inline_buffer =
+        reinterpret_cast<const union ArrowBinaryView*>(array->buffers[1]);
+    for (int64_t i = 0; i < array->length; i++) {
+      EXPECT_EQ(inline_buffer[i].inlined.size, 0);
+    }
+  }
+}
+
 TEST(ArrayTest, ArrayTestAppendToFixedSizeBinaryArray) {
   struct ArrowArray array;
   struct ArrowSchema schema;

src/nanoarrow/common/inline_array.h

@@ -589,7 +589,9 @@ static inline ArrowErrorCode ArrowArrayAppendBytes(struct ArrowArray* array,
     bvt.inlined.size = (int32_t)value.size_bytes;
 
     if (value.size_bytes <= NANOARROW_BINARY_VIEW_INLINE_SIZE) {
-      memcpy(bvt.inlined.data, value.data.as_char, value.size_bytes);
+      if (value.size_bytes > 0) {
+        memcpy(bvt.inlined.data, value.data.as_char, value.size_bytes);
+      }
       memset(bvt.inlined.data + bvt.inlined.size, 0,
              NANOARROW_BINARY_VIEW_INLINE_SIZE - bvt.inlined.size);
     } else {