Ruby C extension to use pthread c library

extconf.rb

require 'mkmf'
have_header("pthread.h")
create_makefile("pthread")

# to use the pthread just run
# ruby extconf.rb
# make
# make install

pthread.c

#include "ruby.h"
#include <pthread.h>
#include <string.h>
static VALUE
c_init(VALUE self, VALUE obj, VALUE func)
{
  Check_Type(func, T_STRING);
  pthread_t thread;
  rb_iv_set(self, "@func", func);
  rb_iv_set(self, "@obj", obj);
  rb_iv_set(self, "@thread", thread);
  return self;
}

void *exec_function(void * self)
{
  VALUE func = rb_iv_get(self, "@func");
  VALUE obj = rb_iv_get(self, "@obj");
  char *c_func = StringValuePtr(func);
  printf("\n Calling function : %s\n", c_func);
  if (! rb_respond_to(obj, rb_intern(c_func)))
    rb_raise(rb_eRuntimeError, "target must respond to function");
  rb_funcall(obj, rb_intern(c_func), 0);
  return (void *) 42;
}

int c_pthread_create(VALUE self)
{
  int result;
  VALUE thread = rb_iv_get(self, "@thread");
  printf("\n Thread launch \n");
  result = pthread_create (&thread, NULL, exec_function, (void *) self);
  return INT2NUM(result);
}

int c_pthread_cancel(VALUE self)
{
  int result;
  VALUE thread = rb_iv_get(self, "@thread");
  printf("\n Cancelling thread \n");
  result = pthread_cancel(&thread);
  return INT2NUM(result);
}

int c_pthread_join(VALUE self)
{
  int result;
  VALUE thread = rb_iv_get(self, "@thread");
  printf("\n Waiting for thread terminate \n");
  result = pthread_join(&thread, NULL);
  return INT2NUM(result);
}

VALUE cPthread; 
void Init_pthread() { 
   cPthread = rb_define_class("Pthread", rb_cObject);
   rb_define_method(cPthread, "initialize", c_init, 2);
   rb_define_method(cPthread, "pthread_create", c_pthread_create, 0);
   rb_define_method(cPthread, "pthread_cancel", c_pthread_cancel, 0);
   rb_define_method(cPthread, "pthread_join", c_pthread_join, 0);
}

sample.rb

require 'rubygems'
require 'pthread'

class Threadclass
  
  def run()
    puts "I am runing in thread"
  end

end

th1 = Threadrclass.new
p1 = Pthread.new(th1,'run')
p1.pthread_create