Use std::filesystem for temporary directory location and deletion (#…

…10664)

Addressing a long-standing TODO. Since std::filesystem is available since C++17, use it to recursively delete temporary directories (used for benchmarks, etc.). 
Small step towards portable temp directory/file utilities.

Authors:
  - Vukasin Milovanovic (https://github.com/vuule)

Approvers:
  - Ram (Ramakrishna Prabhu) (https://github.com/rgsl888prabhu)
  - David Wendt (https://github.com/davidwendt)

URL: #10664

cpp/benchmarks/text/subword.cpp

@@ -21,6 +21,7 @@
 #include <cudf_test/column_utilities.hpp>
 #include <cudf_test/column_wrapper.hpp>
 
+#include <filesystem>
 #include <fstream>
 #include <iostream>
 #include <vector>
@@ -29,7 +30,7 @@
 
 static std::string create_hash_vocab_file()
 {
-  std::string dir_template("/tmp");
+  std::string dir_template{std::filesystem::temp_directory_path().string()};
   if (const char* env_p = std::getenv("WORKSPACE")) dir_template = env_p;
   std::string hash_file = dir_template + "/hash_vocab.txt";
   // create a fake hashed vocab text file for this test

cpp/include/cudf_test/file_utilities.hpp

@@ -18,6 +18,7 @@
 
 #include <cstdio>
 #include <cstdlib>
+#include <filesystem>
 #include <string>
 
 #include <ftw.h>
@@ -34,29 +35,22 @@ class temp_directory {
  public:
   temp_directory(const std::string& base_name)
   {
-    std::string dir_template("/tmp");
-    if (const char* env_p = std::getenv("WORKSPACE")) dir_template = env_p;
+    std::string dir_template{std::filesystem::temp_directory_path().string()};
+    if (auto env_p = std::getenv("WORKSPACE")) dir_template = env_p;
+
     dir_template += "/" + base_name + ".XXXXXX";
     auto const tmpdirptr = mkdtemp(const_cast<char*>(dir_template.data()));
-    if (tmpdirptr == nullptr) CUDF_FAIL("Temporary directory creation failure: " + dir_template);
-    _path = dir_template + "/";
-  }
+    CUDF_EXPECTS(tmpdirptr != nullptr, "Temporary directory creation failure: " + dir_template);
 
-  static int rm_files(const char* pathname, const struct stat* sbuf, int type, struct FTW* ftwb)
-  {
-    return std::remove(pathname);
+    _path = dir_template + "/";
   }
 
   temp_directory& operator=(temp_directory const&) = delete;
   temp_directory(temp_directory const&)            = delete;
   temp_directory& operator=(temp_directory&&) = default;
   temp_directory(temp_directory&&)            = default;
 
-  ~temp_directory()
-  {
-    // TODO: should use std::filesystem instead, once C++17 support added
-    nftw(_path.c_str(), rm_files, 10, FTW_DEPTH | FTW_MOUNT | FTW_PHYS);
-  }
+  ~temp_directory() { std::filesystem::remove_all(std::filesystem::path{_path}); }
 
   /**
    * @brief Returns the path of the temporary directory