=== modified file 'src/dired.c'
--- src/dired.c	2014-04-16 19:43:46 +0000
+++ src/dired.c	2014-08-01 08:11:30 +0000
@@ -133,7 +133,7 @@
    In the latter case, ID_FORMAT is passed to Ffile_attributes.  */
 
 Lisp_Object
-directory_files_internal (Lisp_Object directory, Lisp_Object full,
+directory_files_internal (Lisp_Object dir, Lisp_Object full,
 			  Lisp_Object match, Lisp_Object nosort, bool attrs,
 			  Lisp_Object id_format)
 {
@@ -149,6 +149,16 @@
 #ifdef WINDOWSNT
   Lisp_Object w32_save = Qnil;
 #endif
+#ifdef __clang__
+  /* It is suspected that clang (as of 3.4 running with -O2) can
+     optimize DIR away so there is no reference from C stack to
+     this object.  Since this can crash GC, we're using volatile
+     variable to disable such an optimization.  For details, see
+     http://debbugs.gnu.org/cgi/bugreport.cgi?bug=16986#32.  */
+  volatile Lisp_Object directory = dir;
+#else
+  Lisp_Object directory = dir;
+#endif
 
   /* Because of file name handlers, these functions might call
      Ffuncall, and cause a GC.  */