Declaration EXT:NOTSPECIAL. Declarations (PROCLAIM '(SPECIAL variable)) and DEFCONSTANT are undone by the (PROCLAIM '(EXT:NOTSPECIAL variable)) declaration. This declaration can be used only in global PROCLAIM and DECLAIM forms, not in local DECLARE forms. Of course, you cannot expect miracles: functions compiled before the EXT:NOTSPECIAL proclamation was issued will still be treating variable as special even after the EXT:NOTSPECIAL proclamation.

Function EXT:SPECIAL-VARIABLE-P. You can use the function (EXT:SPECIAL-VARIABLE-P symbol &OPTIONAL environment) to check whether the symbol is a special variable. environment of NIL or omitted means use the global environment. You can also obtain the current lexical environment using the macro EXT:THE-ENVIRONMENT (interpreted code only). This function will always return T for global special variables and constant variables.

Declaration (OPTIMIZE (SAFETY 3)) results in “safe” compiled code: function calls are never eliminated. This guarantees the semantics described in [ANSI CL standard] Section 3.5.

The declaration (COMPILE) has the effect that the current form is compiled prior to execution. Examples:

(LOCALLY (DECLARE (compile)) form)

executes a compiled version of form.

(LET ((x 0))
  (FLET ((inc () (DECLARE (compile)) (INCF x))
         (dec () (DECF x)))
    (VALUES #'inc #'dec)))

returns two functions. The first is compiled and increments x, the second is interpreted (slower) and decrements the same x.

The declaration determines what metadata is recorded in the function object: