Compiling and running SWIG for Lua in Ubuntu 16.04 for the truly lazy

Previously, we were able to compile and run SWIG for Lua in Ubuntu 16.04 using a C source file. In this blog entry, we want to do something very similar except that we use a C header file.

We begin with the files needed starting with the header file, example.h:

	double My_variable;
	int fact(int n);
	int my_mod(int x, int y);
	char *get_time();

view raw example.h hosted with ❤ by GitHub

Then, we create the C implementation file, example.c:

	#include <example.h>
	#include <time.h>
	double My_variable = 3.0;
	int fact(int n)
	{
	if (n <= 1) return 1;
	else return n*fact(n-1);
	}
	int my_mod(int x, int y)
	{
	return (x%y);
	}
	char *get_time()
	{
	time_t ltime;
	time(&ltime);
	return ctime(&ltime);
	}

view raw example.c hosted with ❤ by GitHub

Finally, we create the interface file, example.i, which is needed by SWIG:

	%module example
	%{
	/* Includes the header in the wrapper code */
	#include "example.h"
	%}
	/* Parse the header file to generate wrappers */
	%include "example.h"

view raw example.i hosted with ❤ by GitHub

Notice how much simpler this interface file is compared to the previous one. This is why this entry has a subclause "for the truly lazy".

We then call SWIG to create the wrapper file, example_wrap.c:

% swig -lua example.i

Then we compile the generated wrapper file:

% gcc -fPIC -I/usr/include/lua5.2 -c example_wrap.c -o example_wrap.o

We also compile the C source file, example.c:

% gcc -fPIC -I. -c example.c -o example.o

Finally, we create the shared object which is to be used by our Lua script:

% gcc -shared -I/usr/include/lua5.2 example_wrap.o example.o -o example.so

The Lua script is just the same as our previous blog entry. For convenience:

	package.loadlib('./example.so', 'luaopen_example')()
	print(example.My_variable)
	print(example.fact(5))
	print(example.my_mod(5, 3))
	print(example.get_time())

view raw test.lua hosted with ❤ by GitHub

When run:

% lua test.lua
3
120
2
Wed Jun 14 14:56:54 2017

Hope this helps the world. :)