Thread: Breaking up source code into multiple files

Ok, I'm messing around trying to learn C and got my code working but it was just one large .c file. Now I wanted to break it up into multiple files so it would be easier to see what's going on but ran into some issues. I would appreciate any help with this.

main.c

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "functions.h"

int main()
{
	char *name;
	name = strdup_func("Brian Gable");
	struct employee *eptr = malloc(sizeof *eptr);
	
	build_employee( eptr);
	printf("Empolyee name is: %s\n",eptr->name);
	printf("Empolyee age is: %d\n",eptr->age);
	printf("Empolyee address is: %s\n",eptr->address);
	strcpy(eptr->name,name);
	printf("Empolyee name is: %s\n",eptr->name);
	printf("Empolyee age is: %d\n",eptr->age);
	printf("Empolyee address is: %s\n",eptr->address);
	name = substrg(name,1,5);
	printf("Substring: %s\n", name);
	name = reverse_string(name);
	printf("Substring reversed: %s\n", name);
	
	return (0);	
}

functions.c

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "type.h"

void build_employee(struct employee *employee_pointer)
{
	strcpy(employee_pointer->name, "Michael Clark");
	employee_pointer->age = 29;
	strcpy(employee_pointer->address, "3302 Runner Rd Apt 107");
	
}

char *strdup_func(char *instr)
{
	char *outstr;
	if (!instr)
	{
		fprintf(stderr, "strdup: FATAL - NULL argument!\n");
		return(NULL);
	}
	
	outstr = (char *) malloc(sizeof(char) * (strlen(instr)+1) );
	if (!outstr)
	{
		fprintf(stderr, "strdup: FATAL - malloc failed!");
		return(NULL);
	}
	
	strcpy(outstr, instr);
	
	return(outstr);
}

char *substrg(char *first_string, int start, int numchars)
{
	char *p;
	
	int count = 0, length = 0;
	
	length = strlen(first_string);
	
	if(start > length || length < 2 || start < 1)
	{
		return (NULL);
	}
	
	p = (char *) malloc(sizeof(char) * (numchars+1));
	
	start--;
	
	while (count < numchars)
	{
		p[count]= *(first_string+start+count);
		count++;
	}
	p[count] = '\0';	
	return (p);
	
}

char *reverse_string(char *string)
{
	char *p;
	int slen = 0, count = 0;
	slen = strlen(string);
	p = (char *) malloc(sizeof(char) * (slen+1));
	
	while (string[count] != '\0')
	{
		p[--slen]=string[count++];
	}
	
	return (p);
}
void update_employee_name(struct employee *employee_pointer, char new_name[80])
{
	strcpy(employee_pointer->name, new_name);
}

functions.h

Code:

#ifndef FUNC_H
#define FUNC_H

void build_employee(struct employee *employee_pointer);
char *strdup_func(char *instr);
char *substrg(char *first_string, int start, int numchars);
char *reverse_string(char *string);
void update_employee_name(struct employee *employee_pointer, char new_name[80]);

#endif

type.h

Code:

#ifndef TYPE_H
#define TYPE_H

struct employee 
{
    char name[80];
    int age;
    char  address[256];
};

extern struct employee *eptr;

#endif

errors

Code:

main.C: In function ‘int main()’:
main.C:9: warning: deprecated conversion from string constant to ‘char*’
main.C:10: error: invalid application of ‘sizeof’ to incomplete type ‘employee’ 
main.C:10: error: invalid conversion from ‘void*’ to ‘employee*’
main.C:13: error: invalid use of incomplete type ‘struct employee’
functions.h:4: error: forward declaration of ‘struct employee’
main.C:14: error: invalid use of incomplete type ‘struct employee’
functions.h:4: error: forward declaration of ‘struct employee’
main.C:15: error: invalid use of incomplete type ‘struct employee’
functions.h:4: error: forward declaration of ‘struct employee’
main.C:16: error: invalid use of incomplete type ‘struct employee’
functions.h:4: error: forward declaration of ‘struct employee’
main.C:17: error: invalid use of incomplete type ‘struct employee’
functions.h:4: error: forward declaration of ‘struct employee’
main.C:18: error: invalid use of incomplete type ‘struct employee’
functions.h:4: error: forward declaration of ‘struct employee’
main.C:19: error: invalid use of incomplete type ‘struct employee’
functions.h:4: error: forward declaration of ‘struct employee’