* src/fileio.c (check_writable) [CYGWIN]: Return non-zero if UID or

GID is unknown (Bug#10257).

src/ChangeLog

+2011-12-17  Ken Brown  <kbrown@cornell.edu>
+
+	* fileio.c (check_writable) [CYGWIN]: Return non-zero if UID or
+	GID is unknown (Bug#10257).
+
 2011-12-17  Paul Eggert  <eggert@cs.ucla.edu>
 
 	* s/gnu-linux.h: Fix mark_memory typo (Bug#10286).

src/fileio.c

@@ -2416,15 +2416,27 @@ check_writable (const char *filename)
   return (st.st_mode & S_IWRITE || S_ISDIR (st.st_mode));
 #else /* not MSDOS */
 #ifdef HAVE_EUIDACCESS
-  return (euidaccess (filename, 2) >= 0);
-#else
+  int res = (euidaccess (filename, 2) >= 0);
+#ifdef CYGWIN
+  /* euidaccess may have returned failure because Cygwin couldn't
+     determine the file's UID or GID; if so, we return success. */
+  if (!res)
+    {
+      struct stat st;
+      if (stat (filename, &st) < 0)
+        return 0;
+      res = (st.st_uid == -1 || st.st_gid == -1);
+    }
+#endif /* CYGWIN */
+  return res;
+#else /* not HAVE_EUIDACCESS */
   /* Access isn't quite right because it uses the real uid
      and we really want to test with the effective uid.
      But Unix doesn't give us a right way to do it.
      Opening with O_WRONLY could work for an ordinary file,
      but would lose for directories.  */
   return (access (filename, 2) >= 0);
-#endif
+#endif /* not HAVE_EUIDACCESS */
 #endif /* not MSDOS */
 }