define-foreign-library (name-and-options &body pairs)

feature -- A feature expression.
library -- A library designator.
convention -- One of :cdecl (default) or :stdcall
search-path -- A path or list of paths where the library will be searched if not found in system-global directories. Paths specified in a load clause take priority over paths specified as library option, with *foreign-library-directories* having lowest priority.

A Symbol

Creates a new library designator called name. The load-clauses describe how to load that designator when passed to load-foreign-library or use-foreign-library.

When trying to load the library name, the relevant function searches the load-clauses in order for the first one where feature evaluates to true. That happens for any of the following situations:

1. If feature is a symbol present in *features*.
2. If feature is a list, depending on (first feature), a keyword:

   :and

   All of the feature expressions in (rest feature) are true.

   :or

   At least one of the feature expressions in (rest feature) is true.

   :not

   The feature expression (second feature) is not true.

3. Finally, if feature is t, this load-clause is picked unconditionally.

Upon finding the first true feature, the library loader then loads the library. The meaning of "library designator" is described in load-foreign-library.

Functions associated to a library defined by define-foreign-library, e.g. through defcfun's :library option, will inherit the library's options. The precedence is as follows:

1. defcfun/foreign-funcall specific options;
2. load-clause options;
3. global library options (the name-and-options argument)

See "Loading foreign libraries".