fix warnings (#2693)

diff --git a/torch/csrc/autograd/functions/convolution.cpp b/torch/csrc/autograd/functions/convolution.cpp
index 342ae38..08ac7b8 100644
--- a/torch/csrc/autograd/functions/convolution.cpp
+++ b/torch/csrc/autograd/functions/convolution.cpp
@@ -55,7 +55,7 @@
 
 auto ConvParams::is_output_padding_big() const -> bool {
   bool is_big = false;
-  for (int i = 0; i < output_padding.size(); i++) {
+  for (size_t i = 0; i < output_padding.size(); i++) {
     is_big |= (output_padding[i] >= stride[i] || output_padding[i] >= dilation[i]);
   }
   return is_big;
diff --git a/torch/csrc/generic/Tensor.cpp b/torch/csrc/generic/Tensor.cpp
index 5c2298b..9893ece 100644
--- a/torch/csrc/generic/Tensor.cpp
+++ b/torch/csrc/generic/Tensor.cpp
@@ -823,7 +823,7 @@
         if (!indexer) {
           PyErr_Format(PyExc_IndexError,
               "When performing advanced indexing the indexing objects must be LongTensors or "
-              "convertible to LongTensors. The indexing object at position %d is of type %s "
+              "convertible to LongTensors. The indexing object at position %zd is of type %s "
               "and cannot be converted", i, THPUtils_typename(obj));
 
           // Clean up Indexers