The foreign-symbol-address function is used to find out whether a foreign symbol is defined, by looking for it in the foreign-symbol table. If its associated object code has been loaded into the image, its address is returned. Otherwise nil is returned, unless errorp is nil .
The errorp keyword defines the behavior of the function when a symbol has not been defined. If it is non- nil (which is the default value), then an error will be signalled. If it is nil , no error will be reported, and the function will return nil .
The functionp keyword is used to specify the kind of symbol sought. If it is t , foreign-symbol-address will assume that name is the name of a function. If it is nil it will assume that name is the name of a variable. The default value is t .