The standard says "If the expression is a constant expression, it shall have a value greater than zero." Clang gives me a warning that "static 0" has no effect.

The standard says "If the expression is a constant expression, it shall have a value greater than zero." Clang gives me a warning that "static 0" has no effect. NULL is valid as a pointer to a 0-length array, so that makes sense that it wouldn't function as a non-NULL assertion.