warning Language C: assignment makes pointer from integer without a cast

Question

I'm trying to call one function inside other but I'm doing something wrong and I don't know what. The error was acused where I call the function verifica_sub.

void subtracao(Lista * lista_1, Lista * lista_2)
{
    No_lista *aux1, *aux2, *aux_res_sub;
    int aux_sub = 0, empresta = 0;

    inicLista(&aux_res_sub);
    aux1 = *lista_1;
    aux2 = *lista_2;
    while (aux1 != NULL)
    {
        aux_sub = aux1->info - aux2->info;
        insereFim(&aux_res_sub, aux_sub);
        aux1 = aux1->prox;
        aux2 = aux2->prox;
    }
    aux_res_sub = verifica_sub(&aux_res_sub);
    exibe(&aux_res_sub);
}

void verifica_sub(Lista * aux_res_sub)
{
    No_lista *aux;

    aux = *aux_res_sub;
    while (aux != NULL)
    {
        if (aux->prox->info < 0)
        {
            aux->info = aux->info - 1;
            aux->prox->info = aux->prox->info + 10;
        }
        aux = aux->prox;
    }

Answer 1

You haven't included enough information to give a good answer to your question.

I did notice however that on the line in question you are trying to assign a the result of a void function to a variable. To do this you need to modify verifica_sub to return a value.

Answer 2

verifica_sub() is used without having been prototyped, so the compiler assumes it returns int . As it's result should be assigned to a pointer variable the compiler issues the warning you observe.

However as verifica_sub() is defined to return "nothing", that is void , assigning it to something doesn't make sense, and won't work anyway.