Fix for logical and syntactical errors in libcudf c++ examples (#15346)

This PR fixes a couple of fatal compile and runtime errors in `libcudf/strings` examples

Authors:
  - Muhammad Haseeb (https://github.com/mhaseeb123)

Approvers:
  - Nghia Truong (https://github.com/ttnghia)
  - Mark Harris (https://github.com/harrism)
  - David Wendt (https://github.com/davidwendt)
  - Bradley Dice (https://github.com/bdice)

URL: #15346

cpp/examples/build.sh

@@ -1,9 +1,11 @@
 #!/bin/bash
 
-# Copyright (c) 2021-2023, NVIDIA CORPORATION.
+# Copyright (c) 2021-2024, NVIDIA CORPORATION.
 
 # libcudf examples build script
 
+set -euo pipefail
+
 # Parallelism control
 PARALLEL_LEVEL=${PARALLEL_LEVEL:-4}
 

cpp/examples/strings/common.hpp

@@ -19,6 +19,7 @@
 #include <cudf/column/column_view.hpp>
 #include <cudf/io/csv.hpp>
 #include <cudf/io/datasource.hpp>
+#include <cudf/strings/strings_column_view.hpp>
 #include <cudf/table/table.hpp>
 #include <cudf/table/table_view.hpp>
 
@@ -110,7 +111,8 @@ int main(int argc, char const** argv)
 
   std::chrono::duration<double> elapsed = std::chrono::steady_clock::now() - st;
   std::cout << "Wall time: " << elapsed.count() << " seconds\n";
-  std::cout << "Output size " << result->view().child(1).size() << " bytes\n";
+  auto const scv = cudf::strings_column_view(result->view());
+  std::cout << "Output size " << scv.chars_size(rmm::cuda_stream_default) << " bytes\n";
 
   return 0;
 }

cpp/examples/strings/custom_optimized.cu

@@ -153,8 +153,12 @@ std::unique_ptr<cudf::column> redact_strings(cudf::column_view const& names,
   redact_kernel<<<blocks, block_size, 0, stream.value()>>>(
     *d_names, *d_visibilities, offsets.data(), chars.data());
 
-  // create column from offsets and chars vectors (no copy is performed)
-  auto result = cudf::make_strings_column(names.size(), std::move(offsets), chars.release(), {}, 0);
+  // create column from offsets vector (move only)
+  auto offsets_column = std::make_unique<cudf::column>(std::move(offsets), rmm::device_buffer{}, 0);
+
+  // create column for chars vector (no copy is performed)
+  auto result = cudf::make_strings_column(
+    names.size(), std::move(offsets_column), chars.release(), 0, rmm::device_buffer{});
 
   // wait for all of the above to finish
   stream.synchronize();