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

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

diff --git a/src/libpspp/abt.h b/src/libpspp/abt.h
index 3801eb86636c14d2d4a73420329d7c568768d630..24d7268a2d6543a383361c50914d796e52e7b6c1 100644 (file)
--- a/src/libpspp/abt.h
+++ b/src/libpspp/abt.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
@@ -150,12 +150,14 @@
    tree paper.  */
 
 #include <stddef.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 abt_data(NODE, STRUCT, MEMBER)                                  \
-        ((STRUCT *) ((char *) (NODE) - offsetof (STRUCT, MEMBER)))
+#define abt_data(NODE, STRUCT, MEMBER)                          \
+        (CHECK_POINTER_HAS_TYPE (NODE, struct abt_node *),      \
+         UP_CAST (NODE, STRUCT, MEMBER))
 
 /* Node in an augmented binary tree. */
 struct abt_node