Fix read buffer overflow in split_directories

* make-relative-prefix.c (split_directories):
        Return early on empty 'name'

From-SVN: r279068

libiberty/ChangeLog

@@ -1,3 +1,8 @@
+2019-12-06  Tim Ruehsen  <tim.ruehsen@gmx.de>
+
+	* make-relative-prefix.c (split_directories):
+	Return early on empty 'name'
+
 2019-11-16  Tim Ruehsen  <tim.ruehsen@gmx.de>
 
 	* cp-demangle.c (d_print_init): Remove const from 4th param.

libiberty/make-relative-prefix.c

@@ -122,6 +122,9 @@ split_directories (const char *name, int *ptr_num_dirs)
   const char *p, *q;
   int ch;
 
+  if (!*name)
+    return NULL;
+
   /* Count the number of directories.  Special case MSDOS disk names as part
      of the initial directory.  */
   p = name;