[Cpp] Fix reduce_array, usub_array and in-situ access to array slice

See Modelica.Blocks.Nonlinear.PadeDelay

Belonging to [master]:
  - #2779

SimulationRuntime/cpp/Core/Math/ArrayOperations.cpp

@@ -224,7 +224,7 @@ template <typename T>
 void promote_array(size_t n, const BaseArray<T>& s, BaseArray<T>& d)
 {
   vector<size_t> ex = s.getDims();
-  for (int i=0; i<n; i++)
+  for (size_t i = ex.size(); i < n; i++)
     ex.push_back(1);
   d.setDims(ex);
   d.assign(s.getData());
@@ -447,12 +447,14 @@ void add_array_scalar(const BaseArray<T>& inputArray, T b, BaseArray<T>& outputA
 template <typename T>
 void usub_array(const BaseArray<T>& a, BaseArray<T>& b)
 {
-  const T* src_data = a.getData();
-  T* dst_data = b.getData();
-  size_t numElems =  a.getNumElems();
-  b.setDims(a.getDims());
-  for (size_t i = 0; i < numElems; i++)
-    dst_data[i] = -src_data[i];
+  size_t nelems =  a.getNumElems();
+  if (nelems > 0) {
+    b.setDims(a.getDims());
+    const T* data = a.getData();
+    T* result = b.getData();
+    for (size_t i = 0; i < nelems; i++)
+      result[i] = -data[i];
+  }
 }
 
 template <typename T>

SimulationRuntime/cpp/Include/Core/Math/ArraySlice.h

@@ -193,7 +193,18 @@ class ArraySliceConst: public BaseArray<T> {
     if (n != getNumElems())
       throw ModelicaSimulationError(MODEL_ARRAY_FUNCTION,
                                     "Wrong number of elements in getDataCopy");
-    getDataDim(_idxs.size(), data);
+    if (n > 0) {
+      const T* base_data = _baseArray.getData();
+      if (base_data <= data && data < base_data + n) {
+        // in-situ access requires an internal copy to avoid side effects,
+        // e.g. v = v[n:-1:1]
+        const T* slice_data = getData();
+        std::copy(slice_data, slice_data + n, data);
+      }
+      else
+        // direct access
+        getDataDim(_idxs.size(), data);
+    }
   }
 
   virtual const T* getData() const {