Multiple definition of first defined here

The problem here is that you are including commands.c in commands.h before the function prototype. Therefore, the C pre-processor inserts the content of commands.c into commands.h before the function prototype. commands.c contains the function definition. As a result, the function definition ends up before than the function declaration causing the error.

The content of commands.h after the pre-processor phase looks like this:

#ifndef COMMANDS_H_
#define COMMANDS_H_

// function definition
void f123(){

}

// function declaration
void f123();

#endif /* COMMANDS_H_ */

This is an error because you can't declare a function after its definition in C. If you swapped #include "commands.c" and the function declaration the error shouldn't happen because, now, the function prototype comes before the function declaration.

However, including a .c file is a bad practice and should be avoided. A better solution for this problem would be to include commands.h in commands.c and link the compiled version of command to the main file. For example:

commands.h

#ifndef COMMANDS_H_
#define COMMANDS_H_

void f123(); // function declaration

#endif

commands.c

#include "commands.h"

void f123(){} // function definition

05-18-2018 #1

Registered User

Multiple definition of ' ' first defined here

So I implemented a linked list and a separate chaining hashtable of a struct called Objective, so that I can implement some functions to work with that struct.

Hashtable.c:

Code:

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

#define hash(A,B) (A%B)

static link *heads;
static int M;

void Init(int m){
    int i;
    M = m;
    heads = (link*)malloc(M*sizeof(link));
    for(i = 0; i < M; i++)
        heads[i] = NULL;
}

pObjective search(unsigned long id){
    int i = hash(id, M);
    return searchList(heads[i], id);
}

void insert(pObjective o){
    int i = hash(o->id, M);
    heads[i] = insertBegin(heads[i], o);
}

void delete(unsigned long id){
    int i = hash(id, M);
    heads[i] = removeList(heads[i], id);
}

link insertBegin(link h, pObjective obj){

link new = (link)malloc(sizeof(struct nodehash));
new->obj = obj;
new->next = h;
return new;

}

pObjective searchList(link h, unsigned long id){
    link t, x;
    for(t = h; t != NULL; t = t->next){
        if(t->obj->id == id)
            x = t;
    }
    return x->obj;

}

link removeList(link h, unsigned long id){
    link t, x, z;
    for(t = h; t != NULL; t = t->next){
        if(t->next->obj->id == id)
            x = t;
    }
    z = x->next;
    x->next = z->next;
    free(z);
    return h; }

Hashtable.h:

Code:

#ifndef HASHTABLE_H#define HASHTABLE_H
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

typedef struct Objective{
    char name [8000];
    unsigned long id, duration, deps [9000];
    int hasDeps;
}*pObjective;

typedef struct nodehash{
    pObjective obj;
    struct nodehash*next;
}*link;


void Init(int M);
pObjective search(unsigned long id);
void insert(pObjective o);
void delete(unsigned long id);
link insertBegin(link h, pObjective obj);
pObjective searchList(link h, unsigned long id);
link removeList(link h, unsigned long id);


 #endif

List.c:

Code:

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



links insertEnd(links head, lObjective obj){

    links t;
    links new = (links)malloc(sizeof(struct node));
    new->obj = obj;
    new->next = NULL;
    if(head == NULL) return new;
    for(t = head; t->next != NULL; t = t->next)
        ;
    t->next = new;
    return head;
}

int checkId(links head, unsigned long id){
    links t;
    int count = 0;
    for(t = head; t != NULL; t = t->next){
        if(t->obj->id == id)
            count++;
    }
    return count;
}

links removeList2(links head, unsigned long id){
    links t, x, z;
    for(t = head; t != NULL; t = t->next){
        if(t->next->obj->id == id)
            x = t;
    }
    z = x->next;
    x->next = z->next;
    free(z);
    return head;
}

void print(links head){
    links t;
    int i;

    for(t = head; t!=NULL; t = t->next){
        printf("%lu %s %lu ", t->obj->id, t->obj->name, t->obj->duration);
        for(i = 0; i < 9000; i++){
            printf("%lu ",t->obj->deps[i]);
        }
        printf("\n");
    } }

List.h:

Code:

#ifndef LISTA_H#define LISTA_H
#include <stdio.h>
#include <stdlib.h>

typedef struct Objectives{
    char name [8000];
    unsigned long id, duration, deps [9000];
    int hasDeps;
}*lObjective;

typedef struct node{
 lObjective obj;
 struct node *next;
}*links;

links head = NULL;

links insertEnd(links head, lObjective obj);
int checkId(links head, unsigned long id);
links removeList2(links head, unsigned long id);
void print(links head);

#endif

Objective.c:

Code:

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


int existsDep(unsigned long dep [9000]){
    int count = 0, i;

    for(i=0; i < 9000; i++){
        if(checkId(head, dep[i]) == 0)
            count++;
    }
    if(count == 0)
        return 1;
    else
        return 0;
}

void newObjective(unsigned long id, char name [8000], unsigned long duration,
  unsigned long dep [9000]){

    int i; 

    pObjective obj = malloc(sizeof(pObjective));
    lObjective ob = malloc(sizeof(lObjective));
    obj->id = id;
    ob->id = id;
    obj->duration = duration;
    ob->duration = duration;
    obj->hasDeps = 1;
    ob->hasDeps= 1;
    strcpy(name, obj->name);
    strcpy(name, ob->name);

    for(i = 0; i < 9000; i++){
        obj->deps[i] = dep[i];
        ob->deps[i] = dep[i];
    }

    if(checkId(head, id) != 0)
        printf("id already exists\n");
    else if(existsDep(dep) == 0){
        printf("no such task\n");
    }    
    else{
        insert(obj);
        insertEnd(head, ob);
    }
    free(obj);
    free(ob);
}

void newObjectiveNoDeps(unsigned long id, char name [8000], unsigned long duration){

    pObjective obj = malloc(sizeof(pObjective));
    lObjective ob = malloc(sizeof(lObjective));
    obj->id = id;
    ob->id = id;
    obj->duration = duration;
    ob->duration = duration;
    obj->hasDeps = 0;
    ob->hasDeps = 0;
    strcpy(name, obj->name);
    strcpy(name, ob->name);

     if(checkId(head, id) != 0)
        printf("id already exists\n");
     else{
        insert(obj);
        insertEnd(head, ob);
    }
    free(obj);  
    free(ob);
}

void removeObj(unsigned long id){
    pObjective obj = search(id);

    if(obj->hasDeps == 1)
        printf("task with depedencies\n");
    else if(checkId(head, obj->id) == 0)
        printf("no such task\n");
    else
        delete(id);
        removeList2(head, id);
}

void depend(unsigned long id){
    pObjective obj = search(id);
    int i;

    if(obj->hasDeps == 0)
        printf("%lu: no depedencies\n", id);
    else if(checkId(head, obj->id) == 0)
        printf("no such task\n");
    else{
        printf("%lu: ",id );
        for(i = 0; i < 9000; i++){
            printf("%lu ", obj->deps[i]);
        }
    }
    printf("\n");
}

void duration(){
    print(head);
}

Objective.h:

Code:

#ifndef OBJECTIVES_H#define OBJECTIVES_H
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "LISTA.h"
#include "HASHTABLE.h"

int existsDep(unsigned long dep [9000]);
void newObjective(unsigned long id, char name [8000], unsigned long duration,
  unsigned long dep [9000]);
void newObjectiveNoDeps(unsigned long id, char name [8000], unsigned long duration);
void removeObj(unsigned long id);
void depend(unsigned long id);
void duration();

#endif

My problem is in the head of the list, i keep getting this error:

Code:

/tmp/ccIa32rv.o:(.bss+0x0): multiple definition of `head'/tmp/ccAvumDO.o:(.bss+0x0): first defined here
/tmp/ccuVImET.o:(.bss+0x0): multiple definition of `head'
/tmp/ccAvumDO.o:(.bss+0x0): first defined here
collect2: error: ld returned 1 exit status

And i don't know where I'm wrong... can anyone help me?

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