bug#10257: 23.3.1 Cygwin: network drives - file is write protected (false positive)

[Ken Brown <kbrown@cornell.edu>]

On 12/14/2011 12:57 PM, Ken Brown wrote:
> On 12/14/2011 12:30 PM, Eli Zaretskii wrote:
>> "Such cases" are those where UID and GID are returned as -1 (I think),
>> see the original report where Jari shows the result of
>> file-attributes.
>
> OK, I could certainly change check_writable to return success if
> euidaccess returns failure and UID and GID are both -1. I'll make a
> patch when I get a chance and let Jari test it.

How does the following patch look?

=== modified file 'src/fileio.c'
--- src/fileio.c	2011-12-05 08:55:25 +0000
+++ src/fileio.c	2011-12-15 02:17:01 +0000
@@ -2416,15 +2416,27 @@
    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 and 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 */
  }

Jari, can you test it and see if it solves your problem?

Ken