Using the library shlib for .DLL and .so files

This section discusses the functionality of the (autoload) library shlib.pl, providing an interface to shared libraries. Currently it supports MS-Windows DLL (.dll ) libraries and Unix .so

(shared object) files.

load_foreign_library( +Lib)

  Equivalent to load_foreign_library(Lib, install).

load_foreign_library( +Lib, +Entry)

  Search for the given foreign library and link it to the current SWI-Prolog instance. The library may be specified with or without the extension. It is searched for using the operating-system defined searching mechanism. If the library can be loaded, the function called Entry will be called without arguments. The return value of the function is ignored.

The Entry function will normally call PL_register_foreign() to declare functions in the library as foreign predicates.

unload_foreign_library( +Lib)

  If the foreign library defines the function uninstall , this function will be called without arguments and its return value is ignored. Next, abolish/2 is used to remove all known foreign predicates defined in the library. Finally the library itself is detatched from the process.

current_foreign_library( -Lib, -Predicates)

  Query the currently loaded foreign libraries and their predicates. Predicates is a list with elements of the form Module:Head, indicating the predicates installed with PL_register_foreign().

Figure connects a Windows message-box using a foreign function. This example was tested using Windows-NT and Microsoft Visual C++ 2.0.

  
Figure: MessageBox() example in Windows-NT