diff --git a/cpp/src/binaryop/compiled/binary_ops.cu b/cpp/src/binaryop/compiled/binary_ops.cu
index 2b38224864a..7b0139a0082 100644
--- a/cpp/src/binaryop/compiled/binary_ops.cu
+++ b/cpp/src/binaryop/compiled/binary_ops.cu
@@ -43,7 +43,7 @@ struct scalar_as_column_device_view {
   template <typename T, std::enable_if_t<(is_fixed_width<T>())>* = nullptr>
   return_type operator()(scalar const& s,
                          rmm::cuda_stream_view stream,
-                         rmm::mr::device_memory_resource* mr)
+                         rmm::mr::device_memory_resource*)
   {
     auto& h_scalar_type_view = static_cast<cudf::scalar_type_t<T>&>(const_cast<scalar&>(s));
     auto col_v =
@@ -201,7 +201,6 @@ struct null_considering_binop {
                                      rmm::cuda_stream_view stream,
                                      rmm::mr::device_memory_resource* mr) const
   {
-    std::unique_ptr<column> out;
     // Create device views for inputs
     auto const lhs_dev_view = get_device_view(lhs);
     auto const rhs_dev_view = get_device_view(rhs);
diff --git a/cpp/src/io/orc/reader_impl.cu b/cpp/src/io/orc/reader_impl.cu
index 1b78d8b8585..83be58f5e56 100644
--- a/cpp/src/io/orc/reader_impl.cu
+++ b/cpp/src/io/orc/reader_impl.cu
@@ -176,7 +176,6 @@ size_t gather_stream_info(const size_t stripe_index,
                           const orc::StripeInformation* stripeinfo,
                           const orc::StripeFooter* stripefooter,
                           const std::vector<int>& orc2gdf,
-                          const std::vector<orc_column_meta>& gdf2orc,
                           const std::vector<orc::SchemaType> types,
                           bool use_index,
                           size_t* num_dictionary_entries,
@@ -1203,7 +1202,6 @@ table_with_metadata reader::impl::read(size_type skip_rows,
                                                           stripe_info,
                                                           stripe_footer,
                                                           _col_meta.orc_col_map[level],
-                                                          selected_columns,
                                                           _metadata->get_types(),
                                                           use_index,
                                                           &num_dict_entries,
diff --git a/cpp/src/merge/merge.cu b/cpp/src/merge/merge.cu
index 38025a8a0ed..147db2fdfe7 100644
--- a/cpp/src/merge/merge.cu
+++ b/cpp/src/merge/merge.cu
@@ -225,11 +225,10 @@ struct column_merger {
   explicit column_merger(index_vector const& row_order) : row_order_(row_order) {}
 
   template <typename Element, CUDF_ENABLE_IF(not is_rep_layout_compatible<Element>())>
-  std::unique_ptr<column> operator()(
-    column_view const& lcol,
-    column_view const& rcol,
-    rmm::cuda_stream_view stream,
-    rmm::mr::device_memory_resource* mr = rmm::mr::get_current_device_resource()) const
+  std::unique_ptr<column> operator()(column_view const&,
+                                     column_view const&,
+                                     rmm::cuda_stream_view,
+                                     rmm::mr::device_memory_resource*) const
   {
     CUDF_FAIL("Unsupported type for merge.");
   }
diff --git a/cpp/tests/join/conditional_join_tests.cu b/cpp/tests/join/conditional_join_tests.cu
index 8018d613e05..d566d2086bb 100644
--- a/cpp/tests/join/conditional_join_tests.cu
+++ b/cpp/tests/join/conditional_join_tests.cu
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2020, NVIDIA CORPORATION.
+ * Copyright (c) 2019-2021, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -44,8 +44,6 @@ constexpr cudf::size_type JoinNoneValue =
 // Common column references.
 const auto col_ref_left_0  = cudf::ast::column_reference(0, cudf::ast::table_reference::LEFT);
 const auto col_ref_right_0 = cudf::ast::column_reference(0, cudf::ast::table_reference::RIGHT);
-const auto col_ref_left_1  = cudf::ast::column_reference(1, cudf::ast::table_reference::LEFT);
-const auto col_ref_right_1 = cudf::ast::column_reference(1, cudf::ast::table_reference::RIGHT);
 
 // Common expressions.
 auto left_zero_eq_right_zero =