name is a symbol or string to look up or to create as a foreign symbol. If it is a symbol, the symbol looked for is that which the function lisp-name-to-foreign-name would produce. If name is a string, it is taken literally
If supplied and the symbol is not already defined as a foreign symbol, force forces it to be an undefined foreign symbol. This provides a reference to the symbol so that a subsequent call to read-foreign-modules will attempt to resolve it
It is not usually necessary to use this function.In order to examine whether a foreign symbol is defined, use foreign-symbol-address. The act of defining a foreign function using
makes the symbol undefined, so the use of force is not usually needed.
LispWorks User Guide and Reference Manual - 21 Dec 2011