Make the strings utility reject directories.

PR binutils/21659
	* strings.c (strings_file): Warn about attempts to run strings on
	a directory.

binutils/ChangeLog

@@ -1,3 +1,9 @@
+2017-06-23  Nick Clifton  <nickc@redhat.com>
+
+	PR binutils/21659
+	* strings.c (strings_file): Warn about attempts to run strings on
+	a directory.
+
 2017-06-22  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* readelf.c (decode_x86_feature): Decode

binutils/strings.c

@@ -446,6 +446,11 @@ strings_file (char *file)
 		   file, strerror (errno));
       return FALSE;
     }
+  else if (S_ISDIR (st.st_mode))
+    {
+      non_fatal (_("Warning: '%s' is a directory"), file);
+      return FALSE;
+    }
 
   /* If we weren't told to scan the whole file,
      try to open it as an object file and only look at