Made 'file_posix.cc' POSIX compatible

The `d_type` field is not part of the POSIX specification. Added a compile time check to see if we can use it. When not present fallback to a (slightly more expensive) call to 'stat'.

The reason why I need this is because I'm trying to port Bazel to a POSIX compliant platform. Even though my porting effort might fail miserably ;-) I think having a POSIX implementation which is POSIX compliant would be of benefit to the Bazel project.

Besides the POSIX spec I've based the implementation on information I found here:

* https://stackoverflow.com/questions/2197918/cross-platform-way-of-testing-whether-a-file-is-a-directory
* https://stackoverflow.com/questions/23958040/checking-if-a-dir-entry-returned-by-readdir-is-a-directory-link-or-file#answer-29094555
* https://stackoverflow.com/questions/39429803/how-to-list-first-level-directories-only-in-c/39430337#39430337

Closes #4967.

PiperOrigin-RevId: 192102522

1 files changed, 17 insertions, 13 deletions

diff --git a/src/main/cpp/util/file_posix.cc b/src/main/cpp/util/file_posix.cc
index f143ab125b..5136df0655 100644
--- a/src/main/cpp/util/file_posix.cc
+++ b/src/main/cpp/util/file_posix.cc
@@ -445,22 +445,26 @@ void ForEachDirectoryEntry(const string &path,
 
     string filename(blaze_util::JoinPath(path, ent->d_name));
     bool is_directory;
-    if (ent->d_type == DT_UNKNOWN) {
-      struct stat buf;
-      if (lstat(filename.c_str(), &buf) == -1) {
-        BAZEL_DIE(blaze_exit_code::INTERNAL_ERROR)
-            << "stat failed for filename '" << filename
-            << "': " << GetLastErrorString();
-      }
-      is_directory = S_ISDIR(buf.st_mode);
-    } else {
+// 'd_type' field isn't part of the POSIX spec.
+#ifdef _DIRENT_HAVE_D_TYPE
+    if (ent->d_type != DT_UNKNOWN) {
       is_directory = (ent->d_type == DT_DIR);
+    } else  // NOLINT (the brace is on the next line)
+#endif
+      {
+        struct stat buf;
+        if (lstat(filename.c_str(), &buf) == -1) {
+          BAZEL_DIE(blaze_exit_code::INTERNAL_ERROR)
+              << "stat failed for filename '" << filename
+              << "': " << GetLastErrorString();
+        }
+        is_directory = S_ISDIR(buf.st_mode);
+      }
+
+      consume->Consume(filename, is_directory);
     }
 
-    consume->Consume(filename, is_directory);
+    closedir(dir);
   }
 
-  closedir(dir);
-}
-
 }  // namespace blaze_util