xref: /llvm-project/libcxx/test/support/filesystem_test_helper.h (revision 2b26ee6e790574e05c3c9a562bc37897daf0f384)
1 #ifndef FILESYSTEM_TEST_HELPER_H
2 #define FILESYSTEM_TEST_HELPER_H
3 
4 #include <filesystem>
5 
6 #include <sys/stat.h> // for stat, mkdir, mkfifo
7 #ifndef _WIN32
8 #include <unistd.h> // for ftruncate, link, symlink, getcwd, chdir
9 #include <sys/statvfs.h>
10 #else
11 #include <io.h>
12 #include <direct.h>
13 #include <windows.h> // for CreateSymbolicLink, CreateHardLink
14 #endif
15 
16 #include <cassert>
17 #include <cerrno>
18 #include <chrono>
19 #include <cstdint>
20 #include <cstdio> // for printf
21 #include <cstring>
22 #include <string>
23 #include <system_error>
24 #include <type_traits>
25 #include <vector>
26 
27 #include "assert_macros.h"
28 #include "make_string.h"
29 #include "test_macros.h"
30 #include "format_string.h"
31 
32 // For creating socket files
33 #if !defined(__FreeBSD__) && !defined(__APPLE__) && !defined(_WIN32)
34 # include <sys/socket.h>
35 # include <sys/un.h>
36 #endif
37 namespace fs = std::filesystem;
38 
39 namespace utils {
40 #ifdef _WIN32
41     inline int mkdir(const char* path, int mode) { (void)mode; return ::_mkdir(path); }
42     inline int symlink(const char* oldname, const char* newname, bool is_dir) {
43         DWORD flags = is_dir ? SYMBOLIC_LINK_FLAG_DIRECTORY : 0;
44         if (CreateSymbolicLinkA(newname, oldname,
45                                 flags | SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE))
46           return 0;
47         if (GetLastError() != ERROR_INVALID_PARAMETER)
48           return 1;
49         return !CreateSymbolicLinkA(newname, oldname, flags);
50     }
51     inline int link(const char *oldname, const char* newname) {
52         return !CreateHardLinkA(newname, oldname, NULL);
53     }
54     inline int setenv(const char *var, const char *val, int overwrite) {
55         (void)overwrite;
56         return ::_putenv((std::string(var) + "=" + std::string(val)).c_str());
57     }
58     inline int unsetenv(const char *var) {
59         return ::_putenv((std::string(var) + "=").c_str());
60     }
61     inline bool space(std::string path, std::uintmax_t &capacity,
62                       std::uintmax_t &free, std::uintmax_t &avail) {
63         ULARGE_INTEGER FreeBytesAvailableToCaller, TotalNumberOfBytes,
64                        TotalNumberOfFreeBytes;
65         if (!GetDiskFreeSpaceExA(path.c_str(), &FreeBytesAvailableToCaller,
66                                  &TotalNumberOfBytes, &TotalNumberOfFreeBytes))
67           return false;
68         capacity = TotalNumberOfBytes.QuadPart;
69         free = TotalNumberOfFreeBytes.QuadPart;
70         avail = FreeBytesAvailableToCaller.QuadPart;
71         assert(capacity > 0);
72         assert(free > 0);
73         assert(avail > 0);
74         return true;
75     }
76 #else
77     using ::mkdir;
78     inline int symlink(const char* oldname, const char* newname, bool is_dir) { (void)is_dir; return ::symlink(oldname, newname); }
79     using ::link;
80     using ::setenv;
81     using ::unsetenv;
82     inline bool space(std::string path, std::uintmax_t &capacity,
83                       std::uintmax_t &free, std::uintmax_t &avail) {
84         struct statvfs expect;
85         if (::statvfs(path.c_str(), &expect) == -1)
86           return false;
87         assert(expect.f_bavail > 0);
88         assert(expect.f_bfree > 0);
89         assert(expect.f_bsize > 0);
90         assert(expect.f_blocks > 0);
91         assert(expect.f_frsize > 0);
92         auto do_mult = [&](std::uintmax_t val) {
93             std::uintmax_t fsize = expect.f_frsize;
94             std::uintmax_t new_val = val * fsize;
95             assert(new_val / fsize == val); // Test for overflow
96             return new_val;
97         };
98         capacity = do_mult(expect.f_blocks);
99         free = do_mult(expect.f_bfree);
100         avail = do_mult(expect.f_bavail);
101         return true;
102     }
103 #endif
104 
105     // N.B. libc might define some of the foo[64] identifiers using macros from
106     // foo64 -> foo or vice versa.
107 #if defined(_WIN32)
108     using off64_t = std::int64_t;
109 #elif defined(__MVS__) || defined(__LP64__)
110     using off64_t = ::off_t;
111 #else
112     using ::off64_t;
113 #endif
114 
115     inline FILE* fopen64(const char* pathname, const char* mode) {
116         // Bionic does not distinguish between fopen and fopen64, but fopen64
117         // wasn't added until API 24.
118 #if defined(_WIN32) || defined(__MVS__) || defined(__LP64__) || defined(__BIONIC__)
119         return ::fopen(pathname, mode);
120 #else
121         return ::fopen64(pathname, mode);
122 #endif
123     }
124 
125     inline int ftruncate64(int fd, off64_t length) {
126 #if defined(_WIN32)
127         // _chsize_s sets errno on failure and also returns the error number.
128         return ::_chsize_s(fd, length) ? -1 : 0;
129 #elif defined(__MVS__) || defined(__LP64__)
130         return ::ftruncate(fd, length);
131 #else
132         return ::ftruncate64(fd, length);
133 #endif
134     }
135 
136     inline std::string getcwd() {
137         // Assume that path lengths are not greater than this.
138         // This should be fine for testing purposes.
139         char buf[4096];
140         char* ret = ::getcwd(buf, sizeof(buf));
141         assert(ret && "getcwd failed");
142         return std::string(ret);
143     }
144 
145     inline bool exists(std::string const& path) {
146         struct ::stat tmp;
147         return ::stat(path.c_str(), &tmp) == 0;
148     }
149 } // namespace utils
150 
151 struct scoped_test_env
152 {
153     scoped_test_env() : test_root(available_cwd_path()) {
154 #ifdef _WIN32
155         // Windows mkdir can create multiple recursive directories
156         // if needed.
157         std::string cmd = "mkdir " + test_root.string();
158 #else
159         std::string cmd = "mkdir -p " + test_root.string();
160 #endif
161         int ret = std::system(cmd.c_str());
162         assert(ret == 0);
163 
164         // Ensure that the root_path is fully resolved, i.e. it contains no
165         // symlinks. The filesystem tests depend on that. We do this after
166         // creating the root_path, because `fs::canonical` requires the
167         // path to exist.
168         test_root = fs::canonical(test_root);
169     }
170 
171     ~scoped_test_env() {
172 #ifdef _WIN32
173         std::string cmd = "rmdir /s /q " + test_root.string();
174         int ret = std::system(cmd.c_str());
175         assert(ret == 0);
176 #else
177 #if defined(__MVS__)
178         // The behaviour of chmod -R on z/OS prevents recursive
179         // permission change for directories that do not have read permission.
180         std::string cmd = "find  " + test_root.string() + " -exec chmod 777 {} \\;";
181 #else
182         std::string cmd = "chmod -R 777 " + test_root.string();
183 #endif // defined(__MVS__)
184         int ret = std::system(cmd.c_str());
185 #  if !defined(_AIX) && !defined(__ANDROID__)
186         // On AIX the chmod command will return non-zero when trying to set
187         // the permissions on a directory that contains a bad symlink. This triggers
188         // the assert, despite being able to delete everything with the following
189         // `rm -r` command.
190         //
191         // Android's chmod was buggy in old OSs, but skipping this assert is
192         // sufficient to ensure that the `rm -rf` succeeds for almost all tests:
193         //  - Android L: chmod aborts after one error
194         //  - Android L and M: chmod -R tries to set permissions of a symlink
195         //    target.
196         // LIBCXX-ANDROID-FIXME: Other fixes to consider: place a toybox chmod
197         // onto old devices, re-enable this assert for devices running Android N
198         // and up, rewrite this chmod+rm in C or C++.
199         assert(ret == 0);
200 #  endif
201 
202         cmd = "rm -rf " + test_root.string();
203         ret = std::system(cmd.c_str());
204         assert(ret == 0);
205 #endif
206     }
207 
208     scoped_test_env(scoped_test_env const &) = delete;
209     scoped_test_env & operator=(scoped_test_env const &) = delete;
210 
211     fs::path make_env_path(std::string p) { return sanitize_path(p); }
212 
213     std::string sanitize_path(std::string raw) {
214         assert(raw.find("..") == std::string::npos);
215         std::string root = test_root.string();
216         if (root.compare(0, root.size(), raw, 0, root.size()) != 0) {
217             assert(raw.front() != '\\');
218             fs::path tmp(test_root);
219             tmp /= raw;
220             return tmp.string();
221         }
222         return raw;
223     }
224 
225     // Purposefully using a size potentially larger than off_t here so we can
226     // test the behavior of libc++fs when it is built with _FILE_OFFSET_BITS=64
227     // but the caller is not (std::filesystem also uses uintmax_t rather than
228     // off_t). On a 32-bit system this allows us to create a file larger than
229     // 2GB.
230     std::string create_file(fs::path filename_path, std::uintmax_t size = 0) {
231         std::string filename = sanitize_path(filename_path.string());
232 
233         if (size >
234             static_cast<typename std::make_unsigned<utils::off64_t>::type>(
235                 std::numeric_limits<utils::off64_t>::max())) {
236             std::fprintf(stderr, "create_file(%s, %ju) too large\n",
237                          filename.c_str(), size);
238             std::abort();
239         }
240 
241 #if defined(_WIN32) || defined(__MVS__)
242 #  define FOPEN_CLOEXEC_FLAG ""
243 #else
244 #  define FOPEN_CLOEXEC_FLAG "e"
245 #endif
246         FILE* file = utils::fopen64(filename.c_str(), "w" FOPEN_CLOEXEC_FLAG);
247         if (file == nullptr) {
248             std::fprintf(stderr, "fopen %s failed: %s\n", filename.c_str(),
249                          std::strerror(errno));
250             std::abort();
251         }
252 
253         if (utils::ftruncate64(
254                 fileno(file), static_cast<utils::off64_t>(size)) == -1) {
255             std::fprintf(stderr, "ftruncate %s %ju failed: %s\n", filename.c_str(),
256                          size, std::strerror(errno));
257             std::fclose(file);
258             std::abort();
259         }
260 
261         std::fclose(file);
262         return filename;
263     }
264 
265     std::string create_dir(fs::path filename_path) {
266         std::string filename = filename_path.string();
267         filename = sanitize_path(std::move(filename));
268         int ret = utils::mkdir(filename.c_str(), 0777); // rwxrwxrwx mode
269         assert(ret == 0);
270         return filename;
271     }
272 
273     std::string create_file_dir_symlink(fs::path source_path,
274                                         fs::path to_path,
275                                         bool sanitize_source = true,
276                                         bool is_dir = false) {
277         std::string source = source_path.string();
278         std::string to = to_path.string();
279         if (sanitize_source)
280             source = sanitize_path(std::move(source));
281         to = sanitize_path(std::move(to));
282         int ret = utils::symlink(source.c_str(), to.c_str(), is_dir);
283         assert(ret == 0);
284         return to;
285     }
286 
287     std::string create_symlink(fs::path source_path,
288                                fs::path to_path,
289                                bool sanitize_source = true) {
290         return create_file_dir_symlink(source_path, to_path, sanitize_source,
291                                        false);
292     }
293 
294     std::string create_directory_symlink(fs::path source_path,
295                                          fs::path to_path,
296                                          bool sanitize_source = true) {
297         return create_file_dir_symlink(source_path, to_path, sanitize_source,
298                                        true);
299     }
300 
301     std::string create_hardlink(fs::path source_path, fs::path to_path) {
302         std::string source = source_path.string();
303         std::string to = to_path.string();
304         source = sanitize_path(std::move(source));
305         to = sanitize_path(std::move(to));
306         int ret = utils::link(source.c_str(), to.c_str());
307         assert(ret == 0);
308         return to;
309     }
310 
311 #ifndef _WIN32
312     std::string create_fifo(std::string file) {
313         file = sanitize_path(std::move(file));
314         int ret = ::mkfifo(file.c_str(), 0666); // rw-rw-rw- mode
315         assert(ret == 0);
316         return file;
317     }
318 #endif
319 
320   // Some platforms doesn't support socket files so we shouldn't even
321   // allow tests to call this unguarded.
322 #if !defined(__FreeBSD__) && !defined(__APPLE__) && !defined(_WIN32)
323     std::string create_socket(std::string file) {
324       file = sanitize_path(std::move(file));
325 
326       ::sockaddr_un address;
327       address.sun_family = AF_UNIX;
328 
329 // If file.size() is too big, try to create a file directly inside
330 // /tmp to make sure file path is short enough.
331 // Android platform warns about tmpnam, since the problem does not appear
332 // on Android, let's not apply it for Android.
333 #  if !defined(__ANDROID__)
334     if (file.size() > sizeof(address.sun_path)) {
335       file = std::tmpnam(nullptr);
336     }
337 #  endif
338     assert(file.size() <= sizeof(address.sun_path));
339     ::strncpy(address.sun_path, file.c_str(), sizeof(address.sun_path));
340     int fd = ::socket(AF_UNIX, SOCK_STREAM, 0);
341     assert(::bind(fd, reinterpret_cast<::sockaddr*>(&address), sizeof(address)) == 0);
342     return file;
343   }
344 #endif
345 
346     fs::path test_root;
347 
348 private:
349     // This could potentially introduce a filesystem race if multiple
350     // scoped_test_envs were created concurrently in the same test (hence
351     // sharing the same cwd). However, it is fairly unlikely to happen as
352     // we generally don't use scoped_test_env from multiple threads, so
353     // this is deemed acceptable.
354     // The cwd.filename() itself isn't unique across all tests in the suite,
355     // so start the numbering from a hash of the full cwd, to avoid
356     // different tests interfering with each other.
357     static inline fs::path available_cwd_path() {
358         fs::path const cwd = utils::getcwd();
359         fs::path const tmp = fs::temp_directory_path();
360         std::string base = cwd.filename().string();
361         std::size_t i = std::hash<std::string>()(cwd.string());
362         fs::path p = tmp / (base + "-static_env." + std::to_string(i));
363         while (utils::exists(p.string())) {
364             p = tmp / (base + "-static_env." + std::to_string(++i));
365         }
366         return p;
367     }
368 };
369 
370 /// This class generates the following tree:
371 ///
372 ///     static_test_env
373 ///     |-- bad_symlink -> dne
374 ///     |-- dir1
375 ///     |   |-- dir2
376 ///     |   |   |-- afile3
377 ///     |   |   |-- dir3
378 ///     |   |   |   `-- file5
379 ///     |   |   |-- file4
380 ///     |   |   `-- symlink_to_dir3 -> dir3
381 ///     |   `-- file1
382 ///     |   `-- file2
383 ///     |-- empty_file
384 ///     |-- non_empty_file
385 ///     |-- symlink_to_dir -> dir1
386 ///     `-- symlink_to_empty_file -> empty_file
387 ///
388 class static_test_env {
389     scoped_test_env env_;
390 public:
391     static_test_env() {
392         env_.create_symlink("dne", "bad_symlink", false);
393         env_.create_dir("dir1");
394         env_.create_dir("dir1/dir2");
395         env_.create_file("dir1/dir2/afile3");
396         env_.create_dir("dir1/dir2/dir3");
397         env_.create_file("dir1/dir2/dir3/file5");
398         env_.create_file("dir1/dir2/file4");
399         env_.create_directory_symlink("dir3", "dir1/dir2/symlink_to_dir3", false);
400         env_.create_file("dir1/file1");
401         env_.create_file("dir1/file2", 42);
402         env_.create_file("empty_file");
403         env_.create_file("non_empty_file", 42);
404         env_.create_directory_symlink("dir1", "symlink_to_dir", false);
405         env_.create_symlink("empty_file", "symlink_to_empty_file", false);
406     }
407 
408     const fs::path Root = env_.test_root;
409 
410     fs::path makePath(fs::path const& p) const {
411         // env_path is expected not to contain symlinks.
412         fs::path const& env_path = Root;
413         return env_path / p;
414     }
415 
416     const std::vector<fs::path> TestFileList = {
417         makePath("empty_file"),
418         makePath("non_empty_file"),
419         makePath("dir1/file1"),
420         makePath("dir1/file2")
421     };
422 
423     const std::vector<fs::path> TestDirList = {
424         makePath("dir1"),
425         makePath("dir1/dir2"),
426         makePath("dir1/dir2/dir3")
427     };
428 
429     const fs::path File          = TestFileList[0];
430     const fs::path Dir           = TestDirList[0];
431     const fs::path Dir2          = TestDirList[1];
432     const fs::path Dir3          = TestDirList[2];
433     const fs::path SymlinkToFile = makePath("symlink_to_empty_file");
434     const fs::path SymlinkToDir  = makePath("symlink_to_dir");
435     const fs::path BadSymlink    = makePath("bad_symlink");
436     const fs::path DNE           = makePath("DNE");
437     const fs::path EmptyFile     = TestFileList[0];
438     const fs::path NonEmptyFile  = TestFileList[1];
439     const fs::path CharFile      = "/dev/null"; // Hopefully this exists
440 
441     const std::vector<fs::path> DirIterationList = {
442         makePath("dir1/dir2"),
443         makePath("dir1/file1"),
444         makePath("dir1/file2")
445     };
446 
447     const std::vector<fs::path> DirIterationListDepth1 = {
448         makePath("dir1/dir2/afile3"),
449         makePath("dir1/dir2/dir3"),
450         makePath("dir1/dir2/symlink_to_dir3"),
451         makePath("dir1/dir2/file4"),
452     };
453 
454     const std::vector<fs::path> RecDirIterationList = {
455         makePath("dir1/dir2"),
456         makePath("dir1/file1"),
457         makePath("dir1/file2"),
458         makePath("dir1/dir2/afile3"),
459         makePath("dir1/dir2/dir3"),
460         makePath("dir1/dir2/symlink_to_dir3"),
461         makePath("dir1/dir2/file4"),
462         makePath("dir1/dir2/dir3/file5")
463     };
464 
465     const std::vector<fs::path> RecDirFollowSymlinksIterationList = {
466         makePath("dir1/dir2"),
467         makePath("dir1/file1"),
468         makePath("dir1/file2"),
469         makePath("dir1/dir2/afile3"),
470         makePath("dir1/dir2/dir3"),
471         makePath("dir1/dir2/file4"),
472         makePath("dir1/dir2/dir3/file5"),
473         makePath("dir1/dir2/symlink_to_dir3"),
474         makePath("dir1/dir2/symlink_to_dir3/file5"),
475     };
476 };
477 
478 struct CWDGuard {
479   std::string oldCwd_;
480   CWDGuard() : oldCwd_(utils::getcwd()) { }
481   ~CWDGuard() {
482     int ret = ::chdir(oldCwd_.c_str());
483     assert(ret == 0 && "chdir failed");
484   }
485 
486   CWDGuard(CWDGuard const&) = delete;
487   CWDGuard& operator=(CWDGuard const&) = delete;
488 };
489 
490 // We often need to test that the error_code was cleared if no error occurs
491 // this function returns an error_code which is set to an error that will
492 // never be returned by the filesystem functions.
493 inline std::error_code GetTestEC(unsigned Idx = 0) {
494   using std::errc;
495   auto GetErrc = [&]() {
496     switch (Idx) {
497     case 0:
498       return errc::address_family_not_supported;
499     case 1:
500       return errc::address_not_available;
501     case 2:
502       return errc::address_in_use;
503     case 3:
504       return errc::argument_list_too_long;
505     default:
506       assert(false && "Idx out of range");
507       std::abort();
508     }
509   };
510   return std::make_error_code(GetErrc());
511 }
512 
513 inline bool ErrorIsImp(const std::error_code& ec,
514                        std::vector<std::errc> const& errors) {
515   std::error_condition cond = ec.default_error_condition();
516   for (auto errc : errors) {
517     if (cond.value() == static_cast<int>(errc))
518       return true;
519   }
520   return false;
521 }
522 
523 template <class... ErrcT>
524 inline bool ErrorIs(const std::error_code& ec, std::errc First, ErrcT... Rest) {
525   std::vector<std::errc> errors = {First, Rest...};
526   return ErrorIsImp(ec, errors);
527 }
528 
529 // Provide our own Sleep routine since std::this_thread::sleep_for is not
530 // available in single-threaded mode.
531 template <class Dur> void SleepFor(Dur dur) {
532     using namespace std::chrono;
533 #if !_LIBCPP_HAS_MONOTONIC_CLOCK
534     using Clock = system_clock;
535 #else
536     using Clock = steady_clock;
537 #endif
538     const auto wake_time = Clock::now() + dur;
539     while (Clock::now() < wake_time)
540         ;
541 }
542 
543 inline fs::perms NormalizeExpectedPerms(fs::perms P) {
544 #ifdef _WIN32
545   // On Windows, fs::perms only maps down to one bit stored in the filesystem,
546   // a boolean readonly flag.
547   // Normalize permissions to the format it gets returned; all fs entries are
548   // read+exec for all users; writable ones also have the write bit set for
549   // all users.
550   P |= fs::perms::owner_read | fs::perms::group_read | fs::perms::others_read;
551   P |= fs::perms::owner_exec | fs::perms::group_exec | fs::perms::others_exec;
552   fs::perms Write =
553       fs::perms::owner_write | fs::perms::group_write | fs::perms::others_write;
554   if ((P & Write) != fs::perms::none)
555     P |= Write;
556 #endif
557   return P;
558 }
559 
560 struct ExceptionChecker {
561   std::errc expected_err;
562   fs::path expected_path1;
563   fs::path expected_path2;
564   unsigned num_paths;
565   const char* func_name;
566   std::string opt_message;
567 
568   explicit ExceptionChecker(std::errc first_err, const char* fun_name,
569                             std::string opt_msg = {})
570       : expected_err{first_err}, num_paths(0), func_name(fun_name),
571         opt_message(opt_msg) {}
572   explicit ExceptionChecker(fs::path p, std::errc first_err,
573                             const char* fun_name, std::string opt_msg = {})
574       : expected_err(first_err), expected_path1(p), num_paths(1),
575         func_name(fun_name), opt_message(opt_msg) {}
576 
577   explicit ExceptionChecker(fs::path p1, fs::path p2, std::errc first_err,
578                             const char* fun_name, std::string opt_msg = {})
579       : expected_err(first_err), expected_path1(p1), expected_path2(p2),
580         num_paths(2), func_name(fun_name), opt_message(opt_msg) {}
581 
582   void operator()(fs::filesystem_error const& Err) {
583     assert(ErrorIsImp(Err.code(), {expected_err}));
584     assert(Err.path1() == expected_path1);
585     assert(Err.path2() == expected_path2);
586 #ifndef _WIN32
587     // On Windows, the error strings are windows error code strings, and don't
588     // match textually with the strings generated for generic std::errc::*.
589     LIBCPP_ONLY(check_libcxx_string(Err));
590 #endif
591   }
592 
593   void check_libcxx_string(fs::filesystem_error const& Err) {
594     std::string message = std::make_error_code(expected_err).message();
595 
596     std::string additional_msg = "";
597     if (!opt_message.empty()) {
598       additional_msg = opt_message + ": ";
599     }
600     auto transform_path = [](const fs::path& p) {
601       return "\"" + p.string() + "\"";
602     };
603     std::string format = [&]() -> std::string {
604       switch (num_paths) {
605       case 0:
606         return format_string("filesystem error: in %s: %s%s", func_name,
607                              additional_msg, message);
608       case 1:
609         return format_string("filesystem error: in %s: %s%s [%s]", func_name,
610                              additional_msg, message,
611                              transform_path(expected_path1).c_str());
612       case 2:
613         return format_string("filesystem error: in %s: %s%s [%s] [%s]",
614                              func_name, additional_msg, message,
615                              transform_path(expected_path1).c_str(),
616                              transform_path(expected_path2).c_str());
617       default:
618         TEST_FAIL("unexpected case");
619         return "";
620       }
621     }();
622     assert(format == Err.what());
623     if (format != Err.what()) {
624       std::fprintf(stderr, "filesystem_error::what() does not match expected output:\n");
625       std::fprintf(stderr, "  expected: \"%s\"\n", format.c_str());
626       std::fprintf(stderr, "  actual:   \"%s\"\n\n", Err.what());
627     }
628   }
629 
630   ExceptionChecker(ExceptionChecker const&) = delete;
631   ExceptionChecker& operator=(ExceptionChecker const&) = delete;
632 
633 };
634 
635 inline fs::path GetWindowsInaccessibleDir() {
636   // Only makes sense on windows, but the code can be compiled for
637   // any platform.
638   const fs::path dir("C:\\System Volume Information");
639   std::error_code ec;
640   const fs::path root("C:\\");
641   for (const auto &ent : fs::directory_iterator(root, ec)) {
642     if (ent != dir)
643       continue;
644     // Basic sanity checks on the directory_entry
645     if (!ent.exists() || !ent.is_directory()) {
646       std::fprintf(stderr, "The expected inaccessible directory \"%s\" was found "
647                            "but doesn't behave as expected, skipping tests "
648                            "regarding it\n", dir.string().c_str());
649       return fs::path();
650     }
651     // Check that it indeed is inaccessible as expected
652     (void)fs::exists(ent, ec);
653     if (!ec) {
654       std::fprintf(stderr, "The expected inaccessible directory \"%s\" was found "
655                            "but seems to be accessible, skipping tests "
656                            "regarding it\n", dir.string().c_str());
657       return fs::path();
658     }
659     return ent;
660   }
661   std::fprintf(stderr, "No inaccessible directory \"%s\" found, skipping tests "
662                        "regarding it\n", dir.string().c_str());
663   return fs::path();
664 }
665 
666 #endif /* FILESYSTEM_TEST_HELPER_H */
667