[llvm] r366486 - FileSystem: Check for DTTOIF alone, not _DIRENT_HAVE_D_TYPE

[Jordan Rose via llvm-commits]

Author: jrose
Date: Thu Jul 18 13:05:11 2019
New Revision: 366486

URL: http://llvm.org/viewvc/llvm-project?rev=366486&view=rev
Log:
FileSystem: Check for DTTOIF alone, not _DIRENT_HAVE_D_TYPE

While 'd_type' is a non-standard extension to `struct dirent`, only
glibc signals its presence with a macro '_DIRENT_HAVE_D_TYPE'.
However, any platform with 'd_type' also includes a way to convert to
mode_t values using the macro 'DTTOIF', so we can check for that alone
and still be confident that the 'd_type' member exists.

(If this turns out to be wrong, I'll go back and set up an actual
CMake check.)

I couldn't think of how to write a test for this, because I couldn't
think of how to test that a 'stat' call doesn't happen without
controlling the filesystem or intercepting 'stat', and there's no good
cross-platform way to do that that I know of.

Follow-up (almost a year later) to r342089.

rdar://problem/50592673
https://reviews.llvm.org/D64940

Modified:
    llvm/trunk/lib/Support/Unix/Path.inc

Modified: llvm/trunk/lib/Support/Unix/Path.inc
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Unix/Path.inc?rev=366486&r1=366485&r2=366486&view=diff
==============================================================================
--- llvm/trunk/lib/Support/Unix/Path.inc (original)
+++ llvm/trunk/lib/Support/Unix/Path.inc Thu Jul 18 13:05:11 2019
@@ -833,7 +833,10 @@ std::error_code detail::directory_iterat
 static file_type direntType(dirent* Entry) {
   // Most platforms provide the file type in the dirent: Linux/BSD/Mac.
   // The DTTOIF macro lets us reuse our status -> type conversion.
-#if defined(_DIRENT_HAVE_D_TYPE) && defined(DTTOIF)
+  // Note that while glibc provides a macro to see if this is supported,
+  // _DIRENT_HAVE_D_TYPE, it's not defined on BSD/Mac, so we test for the
+  // d_type-to-mode_t conversion macro instead.
+#if defined(DTTOIF)
   return typeForMode(DTTOIF(Entry->d_type));
 #else
   // Other platforms such as Solaris require a stat() to get the type.