5.7 Linking embedded applications using plld

The utility program plld may be used to link a combination of C-files and Prolog files into a stand-alone executable. It is a simple Bourne-shell script that automates most of the steps outlined in the previous sections.

In the normal usage, a copy is made of the default embedding template ... /pl/include/stub.c. Additional foreign predicates are defined and added to the extension table PL_extensions. The main() routine is modified to suit your application. PL_initialise() must be passed the program-name (argv[0]). The other elements of the command-line may be modified. Next, plld is typically invoked as:

plld will first split the options into various groups for both the C-compiler and the Prolog compiler. Next, it will add various default options to the C-compiler and call it to create an executable holding the user's C-code and the Prolog kernel. Then, it will call the SWI-Prolog compiler to create a saved state from the provided Prolog files and finally, it will attach this saved state to the created emulator to create the requested executable.

Below, it is described how the options are split and which additional options are passed.

-help

Print brief synopsis.

-pl prolog

Select the prolog to use. This prolog is used for two purposes: get the home-directory as well as the compiler/linker options and create a saved state of the Prolog code.

-v

Select verbose operation, showing the various programs and their options.

-o outfile

Reserved to specify the final output file.

-llibrary

Specifies a library for the C-compiler. By default, -lpl and the libraries needed by the Prolog kernel are given.

-Llibrary-directory

Specifies a library directory for the C-compiler. By default the directory containing -lpl for the current architecture is passed.

-g | -Iinclude-directory | -Ddefinition

These options are passed to the C-compiler. By default, the include directory containing SWI-Prolog.h is passed. plld adds two additional * -Ddef flags:

-D__SWI_PROLOG__

Indicates the code is to be connected to SWI-Prolog.

-D__SWI_EMBEDDED__

Indicates the creation of an embedded program.

*.o | *.c | *.C | *.cxx | *.cpp

Passed as input files to the C-compiler

*.pl | *.qlf

Passed as input files to the Prolog compiler to create the saved-state.

*

I.e. all other options. These are passed as linker options to the C-compiler.

• 5.7.1 A simple example