+/* PSPP - a program for statistical analysis.
+ Copyright (C) 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
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#ifndef LIBPSPP_CAST_H
+#define LIBPSPP_CAST_H 1
+
+#include <stddef.h>
+
+/* Given expressions A and B, both of which have pointer type,
+ expands to a void expression that causes a compiler warning if
+ A and B are not pointers to qualified or unqualified versions
+ of compatible types. */
+#define CHECK_POINTER_COMPATIBILITY(A, B) ((void) sizeof ((A) == (B)))
+
+/* Given POINTER, a pointer to the given MEMBER within structure
+ STRUCT, returns the address of the STRUCT. */
+#define UP_CAST(POINTER, STRUCT, MEMBER) \
+ (CHECK_POINTER_COMPATIBILITY (&((STRUCT *) 0)->MEMBER, POINTER), \
+ (STRUCT *) ((char *) (POINTER) - offsetof (STRUCT, MEMBER)))
+
+#endif /* libpspp/cast.h */