define-symbol-macro

(define-symbol-macro name expansion)

Defines a global symbol macro: from here on, a reference to name in a value position evaluates expansion in its place, and a setq/setf of name assigns through expansion as a setf place. It is the top-level sibling of symbol-macrolet and follows the same substitution rules -- quoted data, function-namespace positions (#'name, call heads), case-family keys, go tags and block names are never substituted, and an inner binding of the same name (let, a lambda parameter, dolist, ...) shadows it in its scope. name is not a variable: nothing binds it, and the expansion form is re-evaluated at every reference. Returns the name.

The definition must be a top-level form (a progn or eval-when wrapping it is fine, which is the shape cffi:defcvar expands into) and name must be a literal symbol; the compilers resolve the definition when they read the program, so a reference in a form that precedes it does not see it.