Add CHECK_POINTER_HAS_TYPE macro, and use it to make *_data macros safer.

[pspp-builds.git] / src / libpspp / tower.h

diff --git a/src/libpspp/tower.h b/src/libpspp/tower.h
index 246984a2c1bfd6cd1c46100fbe95f84140843a92..9be8231c98ad7c9b0c7fc217a14a513d2813aa92 100644 (file)
--- a/src/libpspp/tower.h
+++ b/src/libpspp/tower.h
@@ -1,5 +1,5 @@
 /* PSPP - a program for statistical analysis.
-   Copyright (C) 2007 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2009 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -51,12 +51,14 @@
 
 #include <stdbool.h>
 #include <libpspp/abt.h>
+#include <libpspp/cast.h>
 
 /* Returns the data structure corresponding to the given NODE,
    assuming that NODE is embedded as the given MEMBER name in
    data type STRUCT. */
-#define tower_data(NODE, STRUCT, MEMBER)                            \
-        ((STRUCT *) ((char *) (NODE) - offsetof (STRUCT, MEMBER)))
+#define tower_data(NODE, STRUCT, MEMBER)                        \
+        (CHECK_POINTER_HAS_TYPE (NODE, struct tower_node *),    \
+         UP_CAST (NODE, STRUCT, MEMBER))
 
 /* A node within a tower. */
 struct tower_node