On calling PL_initialise(), SWI-Prolog searches for a saved-state holding the Prolog predicates that make up the system (or your application). If it fails, it will print the message above and exit.

First of all it will try to identify the running executable. If successful (which requires passing argv[0] from main() on Unix and nothing special on Windows) and the executable contains a state at the end, it is loaded.

Second, it tries to locate the SWI-Prolog home directory. For this, it first checks the environment variable SWI_HOME_DIR. If it exists and points to something that looks like the home-direcory it uses this directory. If not, it assumes this executable is installed in the bin directory of the installation (Unix: bin/architecture ). Finally, it will use the compiled-in installation direcory. It assumes the file boot32.prc to exist in the home directory and containing the required state.

This poses problems for embedded applications that do not have a saved-state associated (see the plld program), are not installed in the same directory as the SWI-Prolog executable and SWI-Prolog is installed as binary package (the compiled-in default is wrong).

solution

The simplest and most robust solution is to use putenv() to put an appropriate path into the environment before calling PL_initialise().

... putenv("SWI_HOME_DIR=C:\\Program Files\\pl"); if ( PL_initialise(argc, argv) ) PL_halt(1); ...

In the final version of your application you link the saved-state to the executable (using plld or cat (Unix)) and comment the putenv() call.

-- JanWielemaker - 01 Oct 2000