fix memory crash when index < 0.

src/TensorFlowNET.Core/NumPy/NDArray.Index.cs

@@ -10,24 +10,32 @@ namespace Tensorflow.NumPy
     {
         public NDArray this[params int[] index]
         {
-            get => _tensor[index.Select(x => new Slice
+            get => GetData(index.Select(x => new Slice
             {
                 Start = x,
                 Stop = x + 1,
                 IsIndex = true
-            }).ToArray()];
+            }));
 
-            set => SetData(index.Select(x => new Slice
+            set => SetData(index.Select(x => 
             {
-                Start = x,
-                Stop = x + 1,
-                IsIndex = true
+                if(x < 0)
+                    x = (int)dims[0] + x;
+                
+                var slice = new Slice
+                {
+                    Start = x,
+                    Stop = x + 1,
+                    IsIndex = true
+                };
+
+                return slice;
             }), value);
         }
 
         public NDArray this[params Slice[] slices]
         {
-            get => _tensor[slices];
+            get => GetData(slices);
             set => SetData(slices, value);
         }
 
@@ -44,6 +52,11 @@ namespace Tensorflow.NumPy
             }
         }
 
+        NDArray GetData(IEnumerable<Slice> slices)
+        {
+            return _tensor[slices.ToArray()];
+        }
+
         void SetData(IEnumerable<Slice> slices, NDArray array)
             => SetData(slices, array, -1, slices.Select(x => 0).ToArray());
 
@@ -61,7 +74,10 @@ namespace Tensorflow.NumPy
             {
 
                 if (slice.Step != 1)
-                    throw new NotImplementedException("");
+                    throw new NotImplementedException("slice.step should == 1");
+
+                if (slice.Start < 0)
+                    throw new NotImplementedException("slice.start should > -1");
 
                 indices[indices.Length - 1] = slice.Start ?? 0;
                 var offset = (ulong)ShapeHelper.GetOffset(shape, indices);

src/TensorFlowNET.Core/NumPy/ShapeHelper.cs

@@ -81,6 +81,9 @@ namespace Tensorflow.NumPy
             for (int i = 0; i < indices.Length; i++)
                 offset += strides[i] * indices[i];
 
+            if (offset < 0)
+                throw new NotImplementedException("");
+
             return offset;
         }
     }

src/TensorFlowNET.Core/Tensors/Tensor.String.cs

@@ -29,7 +29,7 @@ namespace Tensorflow
 
             var tstr = c_api.TF_TensorData(handle);
 #if TRACK_TENSOR_LIFE
-            print($"New TString 0x{handle.ToString("x16")} {AllocationType} Data: 0x{tstr.ToString("x16")}");
+            print($"New TString 0x{handle.ToString("x16")} Data: 0x{tstr.ToString("x16")}");
 #endif
             for (int i = 0; i < buffer.Length; i++)
             {

test/TensorFlowNET.UnitTest/NumPy/Array.Indexing.Test.cs

@@ -5,6 +5,7 @@ using System.Linq;
 using System.Text;
 using Tensorflow;
 using Tensorflow.NumPy;
+using static Tensorflow.Binding;
 
 namespace TensorFlowNET.UnitTest.NumPy
 {
@@ -53,5 +54,14 @@ namespace TensorFlowNET.UnitTest.NumPy
             Assert.AreEqual(y.shape, (1, 2));
             Assert.AreEqual(y, np.array(new[] { 2, 3 }).reshape((1, 2)));
         }
+
+        [TestMethod]
+        public void slice_out_bound()
+        {
+            var input_shape = tf.constant(new int[] { 1, 1 });
+            var input_shape_val = input_shape.numpy();
+            input_shape_val[(int)input_shape.size - 1] = 1;
+            input_shape.Dispose();
+        }
     }
 }