--- /dev/null
+#ifndef CCAN_BUILD_ASSERT_H
+#define CCAN_BUILD_ASSERT_H
+
+/**
+ * BUILD_ASSERT - assert a build-time dependency.
+ * @cond: the compile-time condition which must be true.
+ *
+ * Your compile will fail if the condition isn't true, or can't be evaluated
+ * by the compiler. This can only be used within a function.
+ *
+ * Example:
+ * char *foo_to_char(struct foo *foo)
+ * {
+ * // This code needs string to be at start of foo.
+ * BUILD_ASSERT(offsetof(struct foo, string) == 0);
+ * return (char *)foo;
+ * }
+ */
+#define BUILD_ASSERT(cond) \
+ do { (void) sizeof(char [1 - 2*!(cond)]); } while(0)
+
+/**
+ * EXPR_BUILD_ASSERT - assert a build-time dependency, as an expression.
+ * @cond: the compile-time condition which must be true.
+ *
+ * Your compile will fail if the condition isn't true, or can't be evaluated
+ * by the compiler. This can be used in an expression: its value is "0".
+ *
+ * Example:
+ * #define foo_to_char(foo) \
+ * ((char *)(foo) \
+ * + EXPR_BUILD_ASSERT(offsetof(struct foo, string) == 0))
+ */
+#define EXPR_BUILD_ASSERT(cond) \
+ (sizeof(char [1 - 2*!(cond)]) - 1)
+
+#endif /* CCAN_BUILD_ASSERT_H */