Linkedlist not looping properly
int particle_update(struct particle **head ){
    struct particle *current = *head;
    struct particle *next;
    printf("particle_updaten");

    while(current != NULL){
        while(current != NULL && current->lifespan >=0){
            current->lifespan --;

            current->pos.y = current->pos.y + (current->spd.y * current->dir.y);
            current->pos.x = current->pos.x + (current->spd.x * current->dir.x);
            current->pos.z = current->pos.z + (current->spd.z * current->dir.z);

            current = current->next;
            if (current == NULL)
                current = *head;
        }
    }

    particle_destroy(head);
    return 0;
}

while(current->lifespan >= 0 && current != NULL){

int particle_update(struct particle **head ){

    struct particle * current = *head;
    struct particle * prev = NULL;

    while (current != NULL) {
        // lifespan check
        current->lifespan = (current -> lifespan > 0) ? current->lifespan-1:particle_destroy(&prev, &current);

        // update position of current
        ...


        // increment counter at end of while loop
        prev = current;
        current = current -> next;  //now current is always one node ahead of previous.
    }

    return 0;
}

void particle_destroy(struct particle ** prev, struct particle ** current) {
    if (*current = NULL) return;  //nothing to do

    struct particle * tmp = *current;
    if (*prev != NULL)  { /* need to modify previous node */
        (*prev) -> next = current -> next;
    } else { /* head has expired, so change head ptr to next node */
        (*current) = (*current) -> next;
    }

    /* free resources */

    // do other clean-up, if necessary.
    free(tmp);

    return;
}