((uintptr_t)&(ptr)->member - (uintptr_t)(ptr))
#endif /* !__GNUC__ */
+/*
+ * Prevent an overly clever compiler from optimizing an expression
+ * out, triggering a false positive when building with the
+ * -Wunreachable-code option. false_but_the_compiler_does_not_know_it_
+ * is defined in a compilation unit separate from where the macro is
+ * used, initialized to 0, and never modified.
+ */
+#define NOT_CONSTANT(expr) ((expr) || false_but_the_compiler_does_not_know_it_)
+extern int false_but_the_compiler_does_not_know_it_;
++
+ #ifdef CHECK_ASSERTION_SIDE_EFFECTS
+ #undef assert
+ extern int not_supposed_to_survive;
+ #define assert(expr) ((void)(not_supposed_to_survive || (expr)))
+ #endif /* CHECK_ASSERTION_SIDE_EFFECTS */
+
#endif