C: seperate header/function

/* You need three files: */
/*---------------------------*/
/* b.h */
#include <stdio.h>
#include <gsl/gsl_vector.h>

struct output_template{
  gsl_vector *v1;
  gsl_vector *v2;
};

struct output_template afunc();


/*---------------------------*/
/* b.c */
#include <stdio.h>
#include <gsl/gsl_vector.h>
#include "b.h"

struct output_template afunc(){
  struct output_template output;
  output.v1=gsl_vector_alloc(2);
  output.v2=gsl_vector_alloc(2);

  gsl_vector_set(output.v1,0,0.2);
  gsl_vector_set(output.v1,1,5.7);

  gsl_vector_set(output.v2,0,-0.2);
  gsl_vector_set(output.v2,1,1.5);

  return output;
}

/*---------------------------*/
/* c.c */
#include <stdio.h>
#include <gsl/gsl_vector.h>
#include "b.h"

int main()
{
  struct output_template output=afunc();

  printf("v1_1=%.5f\n",gsl_vector_get(output.v1,0));

  return(0);
}

/*---------------------------*/
/*---Compile these files-----*/
/*--- I use mkl for cblas needed by gsl -----*/

icc -c b.c
icc -c c.c
icc -o c.out b.o c.o -mkl -lgsl

/*---------------------------*/